Type-level accessor for the shape parameter of this graph.
Type-level accessor for the shape parameter of this graph.
Add the given attributes to this Source.
Add the given attributes to this Source. If the specific attribute was already present on this graph this means the added attribute will be more specific than the existing one. If this Source is a composite of multiple graphs, new attributes on the composite will be less specific than attributes set directly on the individual graphs of the composite.
Attaches the given Sink to this Flow, meaning that elements that passes through will also be sent to the Sink.
Attaches the given Sink to this Flow, meaning that elements that passes through will also be sent to the Sink.
It is similar to #wireTap but will backpressure instead of dropping elements when the given Sink is not ready.
Emits when element is available and demand exists both from the Sink and the downstream.
Backpressures when downstream or Sink backpressures
Completes when upstream completes
Cancels when downstream or Sink cancels
Attaches the given Sink to this Flow, meaning that elements that passes through will also be sent to the Sink.
Attaches the given Sink to this Flow, meaning that elements that passes through will also be sent to the Sink.
It is similar to #wireTapMat but will backpressure instead of dropping elements when the given Sink is not ready.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Converts this Java DSL element to its Scala DSL counterpart.
Use the ask
pattern to send a request-reply message to the target ref
actor.
Use the ask
pattern to send a request-reply message to the target ref
actor.
If any of the asks times out it will fail the stream with a akka.pattern.AskTimeoutException.
The mapTo
class parameter is used to cast the incoming responses to the expected response type.
Similar to the plain ask pattern, the target actor is allowed to reply with akka.util.Status
.
An akka.util.Status#Failure
will cause the operator to fail with the cause carried in the Failure
message.
Parallelism limits the number of how many asks can be "in flight" at the same time. Please note that the elements emitted by this operator are in-order with regards to the asks being issued (i.e. same behaviour as mapAsync).
The operator fails with an akka.stream.WatchedActorTerminatedException if the target actor is terminated.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when any of the CompletionStages returned by the provided function complete
Backpressures when the number of futures reaches the configured parallelism and the downstream backpressures
Completes when upstream completes and all futures have been completed and all elements have been emitted
Fails when the passed in actor terminates, or a timeout is exceeded in any of the asks performed
Cancels when downstream cancels
Use the ask
pattern to send a request-reply message to the target ref
actor.
Use the ask
pattern to send a request-reply message to the target ref
actor.
If any of the asks times out it will fail the stream with a akka.pattern.AskTimeoutException.
The mapTo
class parameter is used to cast the incoming responses to the expected response type.
Similar to the plain ask pattern, the target actor is allowed to reply with akka.util.Status
.
An akka.util.Status#Failure
will cause the operator to fail with the cause carried in the Failure
message.
Defaults to parallelism of 2 messages in flight, since while one ask message may be being worked on, the second one still be in the mailbox, so defaulting to sending the second one a bit earlier than when first ask has replied maintains a slightly healthier throughput.
The operator fails with an akka.stream.WatchedActorTerminatedException if the target actor is terminated.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when any of the CompletionStages returned by the provided function complete
Backpressures when the number of futures reaches the configured parallelism and the downstream backpressures
Completes when upstream completes and all futures have been completed and all elements have been emitted
Fails when the passed in actor terminates, or a timeout is exceeded in any of the asks performed
Cancels when downstream cancels
Put an asynchronous boundary around this Source
Put an asynchronous boundary around this Source
Put an asynchronous boundary around this Source
If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses between element emission and downstream demand.
Cancels when downstream cancels
Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them.
Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them. For example a batch step might store received elements in an array up to the allowed max limit if the upstream publisher is faster.
This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when downstream stops backpressuring and there is an aggregated element available
Backpressures when there are max
batched elements and 1 pending element and downstream backpressures
Completes when upstream completes and there is no batched/pending element waiting
Cancels when downstream cancels
See also Source.conflate, Source.batchWeighted
maximum number of elements to batch before backpressuring upstream (must be positive non-zero)
Provides the first state for a batched value using the first unconsumed element as a start
Takes the currently batched value and the current pending element to produce a new aggregate
Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches until the subscriber is ready to accept them.
Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches
until the subscriber is ready to accept them. For example a batch step might concatenate ByteString
elements up to the allowed max limit if the upstream publisher is faster.
This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
Batching will apply for all elements, even if a single element cost is greater than the total allowed limit.
In this case, previous batched elements will be emitted, then the "heavy" element will be emitted (after
being applied with the seed
function) without batching further elements with it, and then the rest of the
incoming elements are batched.
Emits when downstream stops backpressuring and there is a batched element available
Backpressures when there are max
weighted batched elements + 1 pending element and downstream backpressures
Completes when upstream completes and there is no batched/pending element waiting
Cancels when downstream cancels
See also Source.conflate, Source.batch
maximum weight of elements to batch before backpressuring upstream (must be positive non-zero)
a function to compute a single element weight
Provides the first state for a batched value using the first unconsumed element as a start
Takes the currently batched value and the current pending element to produce a new batch
Adds a fixed size buffer in the flow that allows to store elements from a faster upstream until it becomes full.
Adds a fixed size buffer in the flow that allows to store elements from a faster upstream until it becomes full. Depending on the defined akka.stream.OverflowStrategy it might drop elements or backpressure the upstream if there is no space available
Emits when downstream stops backpressuring and there is a pending element in the buffer
Backpressures when downstream backpressures or depending on OverflowStrategy:
Completes when upstream completes and buffered elements has been drained
Cancels when downstream cancels
The size of the buffer in element count
Strategy that is used when incoming elements cannot fit inside the buffer
Transform this stream by applying the given partial function to each of the elements on which the function is defined as they pass through this processing step.
Transform this stream by applying the given partial function to each of the elements on which the function is defined as they pass through this processing step. Non-matching elements are filtered out.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the provided partial function is defined for the element
Backpressures when the partial function is defined for the element and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Transform this stream by testing the type of each of the elements on which the element is an instance of the provided type as they pass through this processing step.
Transform this stream by testing the type of each of the elements on which the element is an instance of the provided type as they pass through this processing step. Non-matching elements are filtered out.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the element is an instance of the provided type
Backpressures when the element is an instance of the provided type and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
If the completion of the stream does not happen until the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the completion of the stream does not happen until the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses before upstream completes
Cancels when downstream cancels
Concatenate this Source with the given one, meaning that once current is exhausted and all result elements have been generated, the given source elements will be produced.
Concatenate this Source with the given one, meaning that once current is exhausted and all result elements have been generated, the given source elements will be produced.
Note that given Source is materialized together with this Flow and just kept from producing elements by asserting back-pressure until its time comes.
If this Source gets upstream error - no elements from the given Source will be pulled.
Emits when element is available from current source or from the given Source when current is completed
Backpressures when downstream backpressures
Completes when given Source completes
Cancels when downstream cancels
Concatenate this Source with the given one, meaning that once current is exhausted and all result elements have been generated, the given source elements will be produced.
Concatenate this Source with the given one, meaning that once current is exhausted and all result elements have been generated, the given source elements will be produced.
Note that given Source is materialized together with this Flow and just kept from producing elements by asserting back-pressure until its time comes.
If this Source gets upstream error - no elements from the given Source will be pulled.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them.
Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the upstream publisher is faster. This version of conflate does not change the output type of the stream. See Source.conflateWithSeed for a more flexible version that can take a seed function and transform elements while rolling up.
This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when downstream stops backpressuring and there is a conflated element available
Backpressures when never
Completes when upstream completes
Cancels when downstream cancels
see also Source.conflateWithSeed Source.batch Source.batchWeighted
Takes the currently aggregated value and the current pending element to produce a new aggregate
Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them.
Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the upstream publisher is faster.
This version of conflate allows to derive a seed from the first element and change the aggregated type to be different than the input type. See Flow.conflate for a simpler version that does not change types.
This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not duplicate elements.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when downstream stops backpressuring and there is a conflated element available
Backpressures when never
Completes when upstream completes
Cancels when downstream cancels
Provides the first state for a conflated value using the first unconsumed element as a start
Takes the currently aggregated value and the current pending element to produce a new aggregate
Shifts elements emission in time by a specified amount.
Shifts elements emission in time by a specified amount. It allows to store elements in internal buffer while waiting for next element to be emitted. Depending on the defined akka.stream.DelayOverflowStrategy it might drop elements or backpressure the upstream if there is no space available in the buffer.
Delay precision is 10ms to avoid unnecessary timer scheduling cycles
Internal buffer has default capacity 16. You can set buffer size by calling withAttributes(inputBuffer)
Emits when there is a pending element in the buffer and configured time for this element elapsed * EmitEarly - strategy do not wait to emit element if buffer is full
Backpressures when depending on OverflowStrategy * Backpressure - backpressures when buffer is full * DropHead, DropTail, DropBuffer - never backpressures * Fail - fails the stream if buffer gets full
Completes when upstream completes and buffered elements has been drained
Cancels when downstream cancels
time to shift all messages
Strategy that is used when incoming elements cannot fit inside the buffer
Detaches upstream demand from downstream demand without detaching the stream rates; in other words acts like a buffer of size 1.
Detaches upstream demand from downstream demand without detaching the stream rates; in other words acts like a buffer of size 1.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Attaches the given Sink to this Flow, meaning that elements will be sent to the Sink
instead of being passed through if the predicate when
returns true
.
Attaches the given Sink to this Flow, meaning that elements will be sent to the Sink
instead of being passed through if the predicate when
returns true
.
Emits when emits when an element is available from the input and the chosen output has demand
Backpressures when the currently chosen output back-pressures
Completes when upstream completes and no output is pending
Cancels when any of the downstreams cancel
Attaches the given Sink to this Flow, meaning that elements will be sent to the Sink
instead of being passed through if the predicate when
returns true
.
Attaches the given Sink to this Flow, meaning that elements will be sent to the Sink
instead of being passed through if the predicate when
returns true
.
#divertTo
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Discard the given number of elements at the beginning of the stream.
Discard the given number of elements at the beginning of the stream.
No elements will be dropped if n
is zero or negative.
Emits when the specified number of elements has been dropped already
Backpressures when the specified number of elements has been dropped and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Discard elements at the beginning of the stream while predicate is true.
Discard elements at the beginning of the stream while predicate is true. No elements will be dropped after predicate first time returned false.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when predicate returned false and for all following stream elements
Backpressures when predicate returned false and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
predicate is evaluated for each new element until first time returns false
Discard the elements received within the given duration at beginning of the stream.
Discard the elements received within the given duration at beginning of the stream.
Emits when the specified time elapsed and a new upstream element arrives
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Allows a faster downstream to progress independently of a slower publisher by extrapolating elements from an older element until new element comes from the upstream.
Allows a faster downstream to progress independently of a slower publisher by extrapolating elements from an older element until new element comes from the upstream. For example an expand step might repeat the last element for the subscriber until it receives an update from upstream.
This element will never "drop" upstream elements as all elements go through at least one extrapolation step. This means that if the upstream is actually faster than the upstream it will be backpressured by the downstream subscriber.
Expand does not support akka.stream.Supervision#restart and akka.stream.Supervision#resume.
Exceptions from the expander
function will complete the stream with failure.
See also #extrapolate for a version that always preserves the original element and allows for an initial "startup" element.
Emits when downstream stops backpressuring
Backpressures when downstream backpressures or iterator runs empty
Completes when upstream completes
Cancels when downstream cancels
Takes the current extrapolation state to produce an output element and the next extrapolation state.
Allows a faster downstream to progress independent of a slower upstream.
Allows a faster downstream to progress independent of a slower upstream.
This is achieved by introducing "extrapolated" elements - based on those from upstream - whenever downstream signals demand.
Extrapolate does not support akka.stream.Supervision#restart and akka.stream.Supervision#resume.
Exceptions from the extrapolate
function will complete the stream with failure.
See also #expand for a version that can overwrite the original element.
Emits when downstream stops backpressuring, AND EITHER upstream emits OR initial element is present OR
extrapolate
is non-empty and applicable
Backpressures when downstream backpressures or current extrapolate
runs empty
Completes when upstream completes and current extrapolate
runs empty
Cancels when downstream cancels
takes the current upstream element and provides a sequence of "extrapolated" elements based on the original, to be emitted in case downstream signals demand.
the initial element to be emitted, in case upstream is able to stall the entire stream.
Allows a faster downstream to progress independent of a slower upstream.
Allows a faster downstream to progress independent of a slower upstream.
This is achieved by introducing "extrapolated" elements - based on those from upstream - whenever downstream signals demand.
Extrapolate does not support akka.stream.Supervision#restart and akka.stream.Supervision#resume.
Exceptions from the extrapolate
function will complete the stream with failure.
See also #expand for a version that can overwrite the original element.
Emits when downstream stops backpressuring, AND EITHER upstream emits OR initial element is present OR
extrapolate
is non-empty and applicable
Backpressures when downstream backpressures or current extrapolate
runs empty
Completes when upstream completes and current extrapolate
runs empty
Cancels when downstream cancels
Takes the current upstream element and provides a sequence of "extrapolated" elements based on the original, to be emitted in case downstream signals demand.
Only pass on those elements that satisfy the given predicate.
Only pass on those elements that satisfy the given predicate.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the given predicate returns true for the element
Backpressures when the given predicate returns true for the element and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Only pass on those elements that NOT satisfy the given predicate.
Only pass on those elements that NOT satisfy the given predicate.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the given predicate returns false for the element
Backpressures when the given predicate returns false for the element and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Transform each input element into a Source
of output elements that is
then flattened into the output stream by concatenation,
fully consuming one Source after the other.
Transform each input element into a Source
of output elements that is
then flattened into the output stream by concatenation,
fully consuming one Source after the other.
Emits when a currently consumed substream has an element available
Backpressures when downstream backpressures
Completes when upstream completes and all consumed substreams complete
Cancels when downstream cancels
Transform each input element into a Source
of output elements that is
then flattened into the output stream by merging, where at most breadth
substreams are being consumed at any given time.
Transform each input element into a Source
of output elements that is
then flattened into the output stream by merging, where at most breadth
substreams are being consumed at any given time.
Emits when a currently consumed substream has an element available
Backpressures when downstream backpressures
Completes when upstream completes and all consumed substreams complete
Cancels when downstream cancels
Similar to scan
but only emits its result when the upstream completes,
after which it also completes.
Similar to scan
but only emits its result when the upstream completes,
after which it also completes. Applies the given function f
towards its current and next value,
yielding the next current value.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
If the function f
throws an exception and the supervision decision is
akka.stream.Supervision#restart current value starts at zero
again
the stream will continue.
Note that the zero
value must be immutable.
Emits when upstream completes
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Similar to fold
but with an asynchronous function.
Similar to fold
but with an asynchronous function.
Applies the given function towards its current and next value,
yielding the next current value.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
If the function f
returns a failure and the supervision decision is
akka.stream.Supervision.Restart current value starts at zero
again
the stream will continue.
Note that the zero
value must be immutable.
Emits when upstream completes
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
This operation demultiplexes the incoming stream into separate output streams, one for each element key.
This operation demultiplexes the incoming stream into separate output streams, one for each element key. The key is computed for each element using the given function. When a new key is encountered for the first time a new substream is opened and subsequently fed with all elements belonging to that key.
The object returned from this method is not a normal Flow,
it is a SubSource. This means that after this operator all transformations
are applied to all encountered substreams in the same fashion. Substream mode
is exited either by closing the substream (i.e. connecting it to a Sink)
or by merging the substreams back together; see the to
and mergeBack
methods
on SubSource for more information.
It is important to note that the substreams also propagate back-pressure as
any other stream, which means that blocking one substream will block the groupBy
operator itself—and thereby all substreams—once all internal or
explicit buffers are filled.
If the group by function f
throws an exception and the supervision decision
is akka.stream.Supervision#stop the stream and substreams will be completed
with failure.
If the group by function f
throws an exception and the supervision decision
is akka.stream.Supervision#resume or akka.stream.Supervision#restart
the element is dropped and the stream and substreams continue.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when an element for which the grouping function returns a group that has not yet been created. Emits the new group
Backpressures when there is an element pending for a group whose substream backpressures
Completes when upstream completes
Cancels when downstream cancels and all substreams cancel
configures the maximum number of substreams (keys) that are supported; if more distinct keys are encountered then the stream fails
This operation demultiplexes the incoming stream into separate output streams, one for each element key.
This operation demultiplexes the incoming stream into separate output streams, one for each element key. The key is computed for each element using the given function. When a new key is encountered for the first time a new substream is opened and subsequently fed with all elements belonging to that key.
WARNING: If allowClosedSubstreamRecreation
is set to false
(default behavior) the operator
keeps track of all keys of streams that have already been closed. If you expect an infinite
number of keys this can cause memory issues. Elements belonging to those keys are drained
directly and not send to the substream.
Note: If allowClosedSubstreamRecreation
is set to true
substream completion and incoming
elements are subject to race-conditions. If elements arrive for a stream that is in the process
of closing these elements might get lost.
The object returned from this method is not a normal Flow,
it is a SubFlow. This means that after this operator all transformations
are applied to all encountered substreams in the same fashion. Substream mode
is exited either by closing the substream (i.e. connecting it to a Sink)
or by merging the substreams back together; see the to
and mergeBack
methods
on SubFlow for more information.
It is important to note that the substreams also propagate back-pressure as
any other stream, which means that blocking one substream will block the groupBy
operator itself—and thereby all substreams—once all internal or
explicit buffers are filled.
If the group by function f
throws an exception and the supervision decision
is akka.stream.Supervision#stop the stream and substreams will be completed
with failure.
If the group by function f
throws an exception and the supervision decision
is akka.stream.Supervision#resume or akka.stream.Supervision#restart
the element is dropped and the stream and substreams continue.
Function f
MUST NOT return null
. This will throw exception and trigger supervision decision mechanism.
Emits when an element for which the grouping function returns a group that has not yet been created. Emits the new group
Backpressures when there is an element pending for a group whose substream backpressures
Completes when upstream completes
Cancels when downstream cancels and all substreams cancel
configures the maximum number of substreams (keys) that are supported; if more distinct keys are encountered then the stream fails
computes the key for each element
enables recreation of already closed substreams if elements with their corresponding keys arrive after completion
Chunk up this stream into groups of the given size, with the last group possibly smaller than requested due to end-of-stream.
Chunk up this stream into groups of the given size, with the last group possibly smaller than requested due to end-of-stream.
n
must be positive, otherwise IllegalArgumentException is thrown.
Emits when the specified number of elements has been accumulated or upstream completed
Backpressures when a group has been assembled and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Chunk up this stream into groups of elements received within a time window, or limited by the weight of the elements, whatever happens first.
Chunk up this stream into groups of elements received within a time window, or limited by the weight of the elements, whatever happens first. Empty groups will not be emitted if no elements are received from upstream. The last group before end-of-stream will contain the buffered elements since the previously emitted group.
Emits when the configured time elapses since the last group has been emitted or weight limit reached
Backpressures when downstream backpressures, and buffered group (+ pending element) weighs more than maxWeight
Completes when upstream completes (emits last group)
Cancels when downstream completes
maxWeight
must be positive, and d
must be greater than 0 seconds, otherwise
IllegalArgumentException is thrown.
Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first.
Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first. Empty groups will not be emitted if no elements are received from upstream. The last group before end-of-stream will contain the buffered elements since the previously emitted group.
Emits when the configured time elapses since the last group has been emitted or n
elements is buffered
Backpressures when downstream backpressures, and there are n+1
buffered elements
Completes when upstream completes (emits last group)
Cancels when downstream completes
n
must be positive, and d
must be greater than 0 seconds, otherwise
IllegalArgumentException is thrown.
If the time between two processed elements exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the time between two processed elements exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses between two emitted elements
Cancels when downstream cancels
Delays the initial element by the specified duration.
Delays the initial element by the specified duration.
Emits when upstream emits an element if the initial delay is already elapsed
Backpressures when downstream backpressures or initial delay is not yet elapsed
Completes when upstream completes
Cancels when downstream cancels
If the first element has not passed through this operator before the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the first element has not passed through this operator before the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses before first element arrives
Cancels when downstream cancels
Interleave is a deterministic merge of the given Source with elements of this Flow.
Interleave is a deterministic merge of the given Source with elements of this Flow.
It first emits segmentSize
number of elements from this flow to downstream, then - same amount for that
source,
then repeat process.
If eagerClose is false and one of the upstreams complete the elements from the other upstream will continue passing through the interleave operator. If eagerClose is true and one of the upstream complete interleave will cancel the other upstream and complete itself.
If this Flow or Source gets upstream error - stream completes with failure.
Emits when element is available from the currently consumed upstream
Backpressures when downstream backpressures. Signal to current
upstream, switch to next upstream when received segmentSize
elements
Completes when the Flow and given Source completes
Cancels when downstream cancels
Interleave is a deterministic merge of the given Source with elements of this Source.
Interleave is a deterministic merge of the given Source with elements of this Source.
It first emits segmentSize
number of elements from this flow to downstream, then - same amount for that
source,
then repeat process.
Example:
Source.from(Arrays.asList(1, 2, 3)).interleave(Source.from(Arrays.asList(4, 5, 6, 7), 2) // 1, 2, 4, 5, 3, 6, 7
After one of sources is complete than all the rest elements will be emitted from the second one
If one of sources gets upstream error - stream completes with failure.
Emits when element is available from the currently consumed upstream
Backpressures when downstream backpressures. Signal to current
upstream, switch to next upstream when received segmentSize
elements
Completes when this Source and given one completes
Cancels when downstream cancels
Interleave is a deterministic merge of the given Source with elements of this Source.
Interleave is a deterministic merge of the given Source with elements of this Source.
It first emits segmentSize
number of elements from this flow to downstream, then - same amount for that
source,
then repeat process.
If eagerClose is false and one of the upstreams complete the elements from the other upstream will continue passing through the interleave operator. If eagerClose is true and one of the upstream complete interleave will cancel the other upstream and complete itself.
If this Flow or Source gets upstream error - stream completes with failure.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Interleave is a deterministic merge of the given Source with elements of this Source.
Interleave is a deterministic merge of the given Source with elements of this Source.
It first emits segmentSize
number of elements from this flow to downstream, then - same amount for that
source,
then repeat process.
After one of sources is complete than all the rest elements will be emitted from the second one
If one of sources gets upstream error - stream completes with failure.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
Additionally can inject start and end marker elements to stream.
Examples:
Source<Integer, ?> nums = Source.from(Arrays.asList(0, 1, 2, 3)); nums.intersperse(","); // 1 , 2 , 3 nums.intersperse("[", ",", "]"); // [ 1 , 2 , 3 ]
Emits when upstream emits (or before with the start
element if provided)
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
Intersperses stream with provided element, similar to how scala.collection.immutable.List.mkString injects a separator between a List's elements.
Additionally can inject start and end marker elements to stream.
Examples:
Source<Integer, ?> nums = Source.from(Arrays.asList(0, 1, 2, 3)); nums.intersperse(","); // 1 , 2 , 3 nums.intersperse("[", ",", "]"); // [ 1 , 2 , 3 ]
In case you want to only prepend or only append an element (yet still use the intercept
feature
to inject a separator between elements, you may want to use the following pattern instead of the 3-argument
version of intersperse (See Source.concat for semantics details):
Source.single(">> ").concat(list.intersperse(",")) list.intersperse(",").concat(Source.single("END"))
Emits when upstream emits (or before with the start
element if provided)
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Injects additional elements if upstream does not emit for a configured amount of time.
Injects additional elements if upstream does not emit for a configured amount of time. In other words, this operator attempts to maintains a base rate of emitted elements towards the downstream.
If the downstream backpressures then no element is injected until downstream demand arrives. Injected elements do not accumulate during this period.
Upstream elements are always preferred over injected elements.
Emits when upstream emits an element or if the upstream was idle for the configured period
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Ensure stream boundedness by limiting the number of elements from upstream.
Ensure stream boundedness by limiting the number of elements from upstream.
If the number of incoming elements exceeds max, it will signal
upstream failure StreamLimitException
downstream.
Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
The stream will be completed without producing any elements if n
is zero
or negative.
Emits when the specified number of elements to take has not yet been reached
Backpressures when downstream backpressures
Completes when the defined number of elements has been taken or upstream completes
Cancels when the defined number of elements has been taken or downstream cancels
See also Flow.take, Flow.takeWithin, Flow.takeWhile
Ensure stream boundedness by evaluating the cost of incoming elements using a cost function.
Ensure stream boundedness by evaluating the cost of incoming elements
using a cost function. Exactly how many elements will be allowed to travel downstream depends on the
evaluated cost of each element. If the accumulated cost exceeds max, it will signal
upstream failure StreamLimitException
downstream.
Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
The stream will be completed without producing any elements if n
is zero
or negative.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the specified number of elements to take has not yet been reached
Backpressures when downstream backpressures
Completes when the defined number of elements has been taken or upstream completes
Cancels when the defined number of elements has been taken or downstream cancels
See also Flow.take, Flow.takeWithin, Flow.takeWhile
Logs elements flowing through the stream as well as completion and erroring.
Logs elements flowing through the stream as well as completion and erroring.
By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
Uses an internally created LoggingAdapter which uses akka.stream.Log
as it's source (use this class to configure slf4j loggers).
Emits when the mapping function returns an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Logs elements flowing through the stream as well as completion and erroring.
Logs elements flowing through the stream as well as completion and erroring.
By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
Uses the given LoggingAdapter for logging.
Emits when the mapping function returns an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Logs elements flowing through the stream as well as completion and erroring.
Logs elements flowing through the stream as well as completion and erroring.
By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
The extract
function will be applied to each element before logging, so it is possible to log only those fields
of a complex object flowing through this element.
Uses an internally created LoggingAdapter which uses akka.stream.Log
as it's source (use this class to configure slf4j loggers).
Emits when the mapping function returns an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Logs elements flowing through the stream as well as completion and erroring.
Logs elements flowing through the stream as well as completion and erroring.
By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be adjusted according to your needs by providing a custom Attributes.LogLevels attribute on the given Flow:
The extract
function will be applied to each element before logging, so it is possible to log only those fields
of a complex object flowing through this element.
Uses the given LoggingAdapter for logging.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the mapping function returns an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Transform this stream by applying the given function to each of the elements as they pass through this processing step.
Transform this stream by applying the given function to each of the elements as they pass through this processing step.
Emits when the mapping function returns an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Transform this stream by applying the given function to each of the elements as they pass through this processing step.
Transform this stream by applying the given function to each of the elements
as they pass through this processing step. The function returns a CompletionStage
and the
value of that future will be emitted downstream. The number of CompletionStages
that shall run in parallel is given as the first argument to
.
These CompletionStages may complete in any order, but the elements that
are emitted downstream are in the same order as received from upstream.mapAsync
If the function f
throws an exception or if the CompletionStage
is completed
with failure and the supervision decision is akka.stream.Supervision#stop
the stream will be completed with failure.
If the function f
throws an exception or if the CompletionStage
is completed
with failure and the supervision decision is akka.stream.Supervision#resume or
akka.stream.Supervision#restart the element is dropped and the stream continues.
The function f
is always invoked on the elements in the order they arrive.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the CompletionStage returned by the provided function finishes for the next element in sequence
Backpressures when the number of CompletionStages reaches the configured parallelism and the downstream backpressures or the first CompletionStage is not completed
Completes when upstream completes and all CompletionStages has been completed and all elements has been emitted
Cancels when downstream cancels
Transform this stream by applying the given function to each of the elements as they pass through this processing step.
Transform this stream by applying the given function to each of the elements
as they pass through this processing step. The function returns a CompletionStage
and the
value of that future will be emitted downstream. The number of CompletionStages
that shall run in parallel is given as the first argument to
.
Each processed element will be emitted downstream as soon as it is ready, i.e. it is possible
that the elements are not emitted downstream in the same order as received from upstream.mapAsyncUnordered
If the function f
throws an exception or if the CompletionStage
is completed
with failure and the supervision decision is akka.stream.Supervision#stop
the stream will be completed with failure.
If the function f
throws an exception or if the CompletionStage
is completed
with failure and the supervision decision is akka.stream.Supervision#resume or
akka.stream.Supervision#restart the element is dropped and the stream continues.
The function f
is always invoked on the elements in the order they arrive (even though the result of the CompletionStages
returned by f
might be emitted in a different order).
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when any of the CompletionStages returned by the provided function complete
Backpressures when the number of CompletionStages reaches the configured parallelism and the downstream backpressures
Completes when upstream completes and all CompletionStages has been completed and all elements has been emitted
Cancels when downstream cancels
Transform each input element into an Iterable
of output elements that is
then flattened into the output stream.
Transform each input element into an Iterable
of output elements that is
then flattened into the output stream.
Make sure that the Iterable
is immutable or at least not modified after
being used as an output sequence. Otherwise the stream may fail with
ConcurrentModificationException
or other more subtle errors may occur.
The returned Iterable
MUST NOT contain null
values,
as they are illegal as stream elements - according to the Reactive Streams specification.
Emits when the mapping function returns an element or there are still remaining elements from the previously calculated collection
Backpressures when downstream backpressures or there are still remaining elements from the previously calculated collection
Completes when upstream completes and all remaining elements has been emitted
Cancels when downstream cancels
While similar to recover this operator can be used to transform an error signal to a different one *without* logging it as an error in the process.
While similar to recover this operator can be used to transform an error signal to a different one *without* logging
it as an error in the process. So in that sense it is NOT exactly equivalent to recover(t => throw t2)
since recover
would log the t2
error.
Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Similarly to recover throwing an exception inside mapError
_will_ be logged.
Emits when element is available from the upstream or upstream is failed and pf returns an element
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
Transform only the materialized value of this Source, leaving all other properties as they were.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Emits when one of the inputs has an element available
Backpressures when downstream backpressures
Completes when all upstreams complete (eagerComplete=false) or one upstream completes (eagerComplete=true), default value is false
Cancels when downstream cancels
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Emits when one of the inputs has an element available
Backpressures when downstream backpressures
Completes when all upstreams complete
Cancels when downstream cancels
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
Merge the given Source to the current one, taking elements as they arrive from input streams, picking randomly when several elements ready.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Merge the given Source to this Source, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available).
Merge the given Source to this Source, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available). This means that possible contiguity of the input streams is not exploited to avoid waiting for elements, this merge will block when one of the inputs does not have more elements (and does not complete).
Emits when all of the inputs have an element available
Backpressures when downstream backpressures
Completes when all upstreams complete
Cancels when downstream cancels
Merge the given Source to this Source, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available).
Merge the given Source to this Source, taking elements as they arrive from input streams, picking always the smallest of the available elements (waiting for one element from each side to be available). This means that possible contiguity of the input streams is not exploited to avoid waiting for elements, this merge will block when one of the inputs does not have more elements (and does not complete).
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Materializes to Pair<Mat, FlowMonitor<<Out>>
, which is unlike most other operators (!),
in which usually the default materialized value keeping semantics is to keep the left value
(by passing Keep.left()
to a *Mat
version of a method).
Materializes to Pair<Mat, FlowMonitor<<Out>>
, which is unlike most other operators (!),
in which usually the default materialized value keeping semantics is to keep the left value
(by passing Keep.left()
to a *Mat
version of a method). This operator is an exception from
that rule and keeps both values since dropping its sole purpose is to introduce that materialized value.
The FlowMonitor
allows monitoring of the current flow. All events are propagated
by the monitor unchanged. Note that the monitor inserts a memory barrier every time it processes an
event, and may therefor affect performance.
Materializes to FlowMonitor[Out]
that allows monitoring of the current flow.
Materializes to FlowMonitor[Out]
that allows monitoring of the current flow. All events are propagated
by the monitor unchanged. Note that the monitor inserts a memory barrier every time it processes an
event, and may therefor affect performance.
The combine
function is used to combine the FlowMonitor
with this flow's materialized value.
Add a
attribute to this Source.name
Provides a secondary source that will be consumed if this source completes without any elements passing by.
Provides a secondary source that will be consumed if this source completes without any elements passing by. As soon as the first element comes through this stream, the alternative will be cancelled.
Note that this Flow will be materialized together with the Source and just kept from producing elements by asserting back-pressure until its time comes or it gets cancelled.
On errors the operator is failed regardless of source of the error.
Emits when element is available from first stream or first stream closed without emitting any elements and an element is available from the second stream
Backpressures when downstream backpressures
Completes when the primary stream completes after emitting at least one element, when the primary stream completes without emitting and the secondary stream already has completed or when the secondary stream completes
Cancels when downstream cancels and additionally the alternative is cancelled as soon as an element passes by from this stream.
Provides a secondary source that will be consumed if this source completes without any elements passing by.
Provides a secondary source that will be consumed if this source completes without any elements passing by. As soon as the first element comes through this stream, the alternative will be cancelled.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Materializes this Source, immediately returning (1) its materialized value, and (2) a new Source that can be used to consume elements from the newly materialized Source.
Takes up to n
elements from the stream (less than n
if the upstream completes before emitting n
elements)
and returns a pair containing a strict sequence of the taken element
and a stream representing the remaining elements.
Takes up to n
elements from the stream (less than n
if the upstream completes before emitting n
elements)
and returns a pair containing a strict sequence of the taken element
and a stream representing the remaining elements. If n is zero or negative, then this will return a pair
of an empty collection and a stream containing the whole upstream unchanged.
In case of an upstream error, depending on the current state
n
elements has been seen, and therefore the substream
has not yet been emittedEmits when the configured number of prefix elements are available. Emits this prefix, and the rest as a substream
Backpressures when downstream backpressures or substream backpressures
Completes when prefix elements has been consumed and substream has been consumed
Cancels when downstream cancels or substream cancels
Prepend the given Source to this one, meaning that once the given source is exhausted and all result elements have been generated, the current source's elements will be produced.
Prepend the given Source to this one, meaning that once the given source is exhausted and all result elements have been generated, the current source's elements will be produced.
Note that the current Source is materialized together with this Flow and just kept from producing elements by asserting back-pressure until its time comes.
If the given Source gets upstream error - no elements from this Source will be pulled.
Emits when element is available from current source or from the given Source when current is completed
Backpressures when downstream backpressures
Completes when given Source completes
Cancels when downstream cancels
Prepend the given Source to this one, meaning that once the given source is exhausted and all result elements have been generated, the current source's elements will be produced.
Prepend the given Source to this one, meaning that once the given source is exhausted and all result elements have been generated, the current source's elements will be produced.
Note that the current Source is materialized together with this Flow and just kept from producing elements by asserting back-pressure until its time comes.
If the given Source gets upstream error - no elements from this Source will be pulled.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
RecoverWith allows to switch to alternative Source on flow failure.
RecoverWith allows to switch to alternative Source on flow failure. It will stay in effect after
a failure has been recovered so that each time there is a failure it is fed into the pf
and a new
Source may be materialized.
Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recoverWith
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and element is available from alternative Source
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
RecoverWith allows to switch to alternative Source on flow failure.
RecoverWith allows to switch to alternative Source on flow failure. It will stay in effect after
a failure has been recovered so that each time there is a failure it is fed into the pf
and a new
Source may be materialized.
Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recoverWith
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and element is available from alternative Source
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
RecoverWithRetries allows to switch to alternative Source on flow failure.
RecoverWithRetries allows to switch to alternative Source on flow failure. It will stay in effect after
a failure has been recovered up to attempts
number of times so that each time there is a failure
it is fed into the pf
and a new Source may be materialized. Note that if you pass in 0, this won't
attempt to recover at all.
A negative attempts
number is interpreted as "infinite", which results in the exact same behavior as recoverWith
.
Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recoverWithRetries
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and element is available from alternative Source
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
Maximum number of retries or -1 to retry indefinitely
the class object of the failure cause
supply the new Source to be materialized
RecoverWithRetries allows to switch to alternative Source on flow failure.
RecoverWithRetries allows to switch to alternative Source on flow failure. It will stay in effect after
a failure has been recovered up to attempts
number of times so that each time there is a failure
it is fed into the pf
and a new Source may be materialized. Note that if you pass in 0, this won't
attempt to recover at all.
A negative attempts
number is interpreted as "infinite", which results in the exact same behavior as recoverWith
.
Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recoverWithRetries
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and element is available from alternative Source
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
Similar to fold
but uses first element as zero element.
Similar to fold
but uses first element as zero element.
Applies the given function towards its current and next value,
yielding the next current value.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when upstream completes
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Shortcut for running this Source
with a fold function.
Shortcut for running this Source
with a fold function.
The given function is invoked for every received element, giving it its previous
output (or the given zero
value) and the element as input.
The returned java.util.concurrent.CompletionStage will be completed with value of the final
function evaluation when the input stream ends, or completed with Failure
if there is a failure is signaled in the stream.
Shortcut for running this Source
with an asynchronous fold function.
Shortcut for running this Source
with an asynchronous fold function.
The given function is invoked for every received element, giving it its previous
output (or the given zero
value) and the element as input.
The returned java.util.concurrent.CompletionStage will be completed with value of the final
function evaluation when the input stream ends, or completed with Failure
if there is a failure is signaled in the stream.
Shortcut for running this Source
with a foreach procedure.
Shortcut for running this Source
with a foreach procedure. The given procedure is invoked
for each received element.
The returned java.util.concurrent.CompletionStage will be completed normally when reaching the
normal end of the stream, or completed exceptionally if there is a failure is signaled in
the stream.
Shortcut for running this Source
with a reduce function.
Shortcut for running this Source
with a reduce function.
The given function is invoked for every received element, giving it its previous
output (from the second ones) an the element as input.
The returned java.util.concurrent.CompletionStage will be completed with value of the final
function evaluation when the input stream ends, or completed with Failure
if there is a failure is signaled in the stream.
If the stream is empty (i.e. completes before signalling any elements), the reduce operator will fail its downstream with a NoSuchElementException, which is semantically in-line with that Scala's standard library collections do in such situations.
Connect this Source
to a Sink
and run it.
Connect this Source
to a Sink
and run it. The returned value is the materialized value
of the Sink
, e.g. the Publisher
of a Sink.asPublisher
.
Similar to fold
but is not a terminal operation,
emits its current value which starts at zero
and then
applies the current and next value to the given function f
,
emitting the next current value.
Similar to fold
but is not a terminal operation,
emits its current value which starts at zero
and then
applies the current and next value to the given function f
,
emitting the next current value.
If the function f
throws an exception and the supervision decision is
akka.stream.Supervision#restart current value starts at zero
again
the stream will continue.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Note that the zero
value must be immutable.
Emits when the function scanning the element returns a new element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Similar to scan
but with a asynchronous function,
emits its current value which starts at zero
and then
applies the current and next value to the given function f
,
emitting a Future
that resolves to the next current value.
Similar to scan
but with a asynchronous function,
emits its current value which starts at zero
and then
applies the current and next value to the given function f
,
emitting a Future
that resolves to the next current value.
If the function f
throws an exception and the supervision decision is
akka.stream.Supervision.Restart current value starts at zero
again
the stream will continue.
If the function f
throws an exception and the supervision decision is
akka.stream.Supervision.Resume current value starts at the previous
current value, or zero when it doesn't have one, and the stream will continue.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Note that the zero
value must be immutable.
Emits when the future returned by f completes
Backpressures when downstream backpressures
Completes when upstream completes and the last future returned by f
completes
Cancels when downstream cancels
See also FlowOps.scan
The shape of a graph is all that is externally visible: its inlets and outlets.
Apply a sliding window over the stream and return the windows as groups of elements, with the last group possibly smaller than requested due to end-of-stream.
Apply a sliding window over the stream and return the windows as groups of elements, with the last group possibly smaller than requested due to end-of-stream.
n
must be positive, otherwise IllegalArgumentException is thrown.
step
must be positive, otherwise IllegalArgumentException is thrown.
Emits when enough elements have been collected within the window or upstream completed
Backpressures when a window has been assembled and downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams. It *ends* the current substream when the predicate is true.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams. It *ends* the current substream when the predicate is true. This means that for the following series of predicate values, three substreams will be produced with lengths 2, 2, and 3:
false, true, // elements go into first substream false, true, // elements go into second substream false, false, true // elements go into third substream
The object returned from this method is not a normal Flow,
it is a SubSource. This means that after this operator all transformations
are applied to all encountered substreams in the same fashion. Substream mode
is exited either by closing the substream (i.e. connecting it to a Sink)
or by merging the substreams back together; see the to
and mergeBack
methods
on SubSource for more information.
It is important to note that the substreams also propagate back-pressure as
any other stream, which means that blocking one substream will block the splitAfter
operator itself—and thereby all substreams—once all internal or
explicit buffers are filled.
If the split predicate p
throws an exception and the supervision decision
is akka.stream.Supervision.Stop the stream and substreams will be completed
with failure.
If the split predicate p
throws an exception and the supervision decision
is akka.stream.Supervision.Resume or akka.stream.Supervision.Restart
the element is dropped and the stream and substreams continue.
Emits when an element passes through. When the provided predicate is true it emits the element and opens a new substream for subsequent element
Backpressures when there is an element pending for the next substream, but the previous is not fully consumed yet, or the substream backpressures
Completes when upstream completes
Cancels when downstream cancels and substreams cancel
See also Source.splitWhen.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams, always beginning a new one with the current element if the given predicate returns true for it.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams, always beginning a new one with the current element if the given predicate returns true for it.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams, always beginning a new one with the current element if the given predicate returns true for it.
This operation applies the given predicate to all incoming elements and emits them to a stream of output streams, always beginning a new one with the current element if the given predicate returns true for it. This means that for the following series of predicate values, three substreams will be produced with lengths 1, 2, and 3:
false, // element goes into first substream true, false, // elements go into second substream true, false, false // elements go into third substream
In case the *first* element of the stream matches the predicate, the first substream emitted by splitWhen will start from that element. For example:
true, false, false // first substream starts from the split-by element true, false // subsequent substreams operate the same way
The object returned from this method is not a normal Flow,
it is a SubSource. This means that after this operator all transformations
are applied to all encountered substreams in the same fashion. Substream mode
is exited either by closing the substream (i.e. connecting it to a Sink)
or by merging the substreams back together; see the to
and mergeBack
methods
on SubSource for more information.
It is important to note that the substreams also propagate back-pressure as
any other stream, which means that blocking one substream will block the splitWhen
operator itself—and thereby all substreams—once all internal or
explicit buffers are filled.
If the split predicate p
throws an exception and the supervision decision
is akka.stream.Supervision.Stop the stream and substreams will be completed
with failure.
If the split predicate p
throws an exception and the supervision decision
is akka.stream.Supervision.Resume or akka.stream.Supervision.Restart
the element is dropped and the stream and substreams continue.
Emits when an element for which the provided predicate is true, opening and emitting a new substream for subsequent element
Backpressures when there is an element pending for the next substream, but the previous is not fully consumed yet, or the substream backpressures
Completes when upstream completes
Cancels when downstream cancels and substreams cancel
See also Source.splitAfter.
API MAY CHANGE
API MAY CHANGE
Transform each input element into an Iterable
of output elements that is
then flattened into the output stream.
Transform each input element into an Iterable
of output elements that is
then flattened into the output stream. The transformation is meant to be stateful,
which is enabled by creating the transformation function anew for every materialization —
the returned function will typically close over mutable objects to store state between
invocations. For the stateless variant see #mapConcat.
Make sure that the Iterable
is immutable or at least not modified after
being used as an output sequence. Otherwise the stream may fail with
ConcurrentModificationException
or other more subtle errors may occur.
The returned Iterable
MUST NOT contain null
values,
as they are illegal as stream elements - according to the Reactive Streams specification.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the mapping function returns an element or there are still remaining elements from the previously calculated collection
Backpressures when downstream backpressures or there are still remaining elements from the previously calculated collection
Completes when upstream completes and all remaining elements has been emitted
Cancels when downstream cancels
Terminate processing (and cancel the upstream publisher) after the given number of elements.
Terminate processing (and cancel the upstream publisher) after the given number of elements. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
The stream will be completed without producing any elements if n
is zero
or negative.
Emits when the specified number of elements to take has not yet been reached
Backpressures when downstream backpressures
Completes when the defined number of elements has been taken or upstream completes
Cancels when the defined number of elements has been taken or downstream cancels
Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time.
Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
The stream will be completed without producing any elements if predicate is false for the first stream element.
Emits when the predicate is true
Backpressures when downstream backpressures
Completes when predicate returned false or upstream completes
Cancels when predicate returned false or downstream cancels
See also Source.limit, Source.limitWeighted
Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, including the first failed element if inclusive is true Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
Terminate processing (and cancel the upstream publisher) after predicate returns false for the first time, including the first failed element if inclusive is true Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
The stream will be completed without producing any elements if predicate is false for the first stream element.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
Emits when the predicate is true
Backpressures when downstream backpressures
Completes when predicate returned false (or 1 after predicate returns false if inclusive
or upstream completes
Cancels when predicate returned false or downstream cancels
See also Source.limit, Source.limitWeighted
Terminate processing (and cancel the upstream publisher) after the given duration.
Terminate processing (and cancel the upstream publisher) after the given duration. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
Note that this can be combined with #take to limit the number of elements within the duration.
Emits when an upstream element arrives
Backpressures when downstream backpressures
Completes when upstream completes or timer fires
Cancels when downstream cancels or timer fires
Sends elements downstream with speed limited to cost/per
.
Sends elements downstream with speed limited to cost/per
. Cost is
calculating for each element individually by calling calculateCost
function.
This operator works for streams when elements have different cost(length).
Streams of ByteString
for example.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and started.
Parameter mode
manages behavior when upstream is faster than throttle rate:
It is recommended to use non-zero burst sizes as they improve both performance and throttling precision by allowing the implementation to avoid using the scheduler when input rates fall below the enforced limit and to reduce most of the inaccuracy caused by the scheduler resolution (which is in the range of milliseconds).
WARNING: Be aware that throttle is using scheduler to slow down the stream. This scheduler has minimal time of triggering
next push. Consequently it will slow down the stream as it has minimal pause for emitting. This can happen in
case burst is 0 and speed is higher than 30 events per second. You need to increase the maximumBurst
if
elements arrive with small interval (30 milliseconds or less). Use the overloaded throttle
method without
maximumBurst
parameter to automatically calculate the maximumBurst
based on the given rate (cost/per
).
In other words the throttler always enforces the rate limit when maximumBurst
parameter is given, but in
certain cases (mostly due to limited scheduler resolution) it enforces a tighter bound than what was prescribed.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
Sends elements downstream with speed limited to cost/per
.
Sends elements downstream with speed limited to cost/per
. Cost is
calculating for each element individually by calling calculateCost
function.
This operator works for streams when elements have different cost(length).
Streams of ByteString
for example.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and
started.
The burst size is calculated based on the given rate (cost/per
) as 0.1 * rate, for example:
- rate < 20/second => burst size 1
- rate 20/second => burst size 2
- rate 100/second => burst size 10
- rate 200/second => burst size 20
The throttle mode
is akka.stream.ThrottleMode.Shaping, which makes pauses before emitting messages to
meet throttle rate.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
Sends elements downstream with speed limited to elements/per
.
Sends elements downstream with speed limited to elements/per
. In other words, this operator set the maximum rate
for emitting messages. This operator works for streams where all elements have the same cost or length.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and started.
Parameter mode
manages behavior when upstream is faster than throttle rate:
It is recommended to use non-zero burst sizes as they improve both performance and throttling precision by allowing the implementation to avoid using the scheduler when input rates fall below the enforced limit and to reduce most of the inaccuracy caused by the scheduler resolution (which is in the range of milliseconds).
WARNING: Be aware that throttle is using scheduler to slow down the stream. This scheduler has minimal time of triggering
next push. Consequently it will slow down the stream as it has minimal pause for emitting. This can happen in
case burst is 0 and speed is higher than 30 events per second. You need to increase the maximumBurst
if
elements arrive with small interval (30 milliseconds or less). Use the overloaded throttle
method without
maximumBurst
parameter to automatically calculate the maximumBurst
based on the given rate (cost/per
).
In other words the throttler always enforces the rate limit when maximumBurst
parameter is given, but in
certain cases (mostly due to limited scheduler resolution) it enforces a tighter bound than what was prescribed.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
Sends elements downstream with speed limited to elements/per
.
Sends elements downstream with speed limited to elements/per
. In other words, this operator set the maximum rate
for emitting messages. This operator works for streams where all elements have the same cost or length.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and
started.
The burst size is calculated based on the given rate (cost/per
) as 0.1 * rate, for example:
- rate < 20/second => burst size 1
- rate 20/second => burst size 2
- rate 100/second => burst size 10
- rate 200/second => burst size 20
The throttle mode
is akka.stream.ThrottleMode.Shaping, which makes pauses before emitting messages to
meet throttle rate.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
Connect this Source to a Sink, concatenating the processing steps of both.
Connect this Source to a Sink, concatenating the processing steps of both.
+----------------------------+
| Resulting RunnableGraph |
| |
| +------+ +------+ |
| | | | | |
| | this | ~Out~> | sink | |
| | | | | |
| +------+ +------+ |
+----------------------------+
The materialized value of the combined Sink will be the materialized
value of the current flow (ignoring the given Sink’s value), use
toMat
if a different strategy is needed.
Connect this Source to a Sink, concatenating the processing steps of both.
Connect this Source to a Sink, concatenating the processing steps of both.
+----------------------------+
| Resulting RunnableGraph |
| |
| +------+ +------+ |
| | | | | |
| | this | ~Out~> | sink | |
| | | | | |
| +------+ +------+ |
+----------------------------+
The combine
function is used to compose the materialized values of this flow and that
Sink into the materialized value of the resulting Sink.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
INTERNAL API.
Transform this Source by appending the given processing operators.
Transform this Source by appending the given processing operators.
+----------------------------+
| Resulting Source |
| |
| +------+ +------+ |
| | | | | |
| | this | ~Out~> | flow | ~~> T
| | | | | |
| +------+ +------+ |
+----------------------------+
The materialized value of the combined Flow will be the materialized
value of the current flow (ignoring the other Flow’s value), use
viaMat
if a different strategy is needed.
Transform this Source by appending the given processing operators.
Transform this Source by appending the given processing operators.
+----------------------------+
| Resulting Source |
| |
| +------+ +------+ |
| | | | | |
| | this | ~Out~> | flow | ~~> T
| | | | | |
| +------+ +------+ |
+----------------------------+
The combine
function is used to compose the materialized values of this flow and that
flow into the materialized value of the resulting Flow.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
The operator fails with an akka.stream.WatchedActorTerminatedException if the target actor is terminated.
The operator fails with an akka.stream.WatchedActorTerminatedException if the target actor is terminated.
Emits when upstream emits
Backpressures when downstream backpressures
Completes when upstream completes
Fails when the watched actor terminates
Cancels when downstream cancels
Materializes to Future[Done]
that completes on getting termination message.
Materializes to Future[Done]
that completes on getting termination message.
The Future completes with success when received complete message from upstream or cancel
from downstream. It fails with the same error when received error message from
downstream.
This is a simplified version of wireTap(Sink)
that takes only a simple procedure.
This is a simplified version of wireTap(Sink)
that takes only a simple procedure.
Elements will be passed into this "side channel" function, and any of its results will be ignored.
If the wire-tap operation is slow (it backpressures), elements that would've been sent to it will be dropped instead.
It is similar to #alsoTo which does backpressure instead of dropping elements.
This operation is useful for inspecting the passed through element, usually by means of side-effecting
operations (such as println
, or emitting metrics), for each element without having to modify it.
For logging signals (elements, completion, error) consider using the log operator instead,
along with appropriate ActorAttributes.createLogLevels
.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels; Note that failures of the f
function will not cause cancellation
Attaches the given Sink to this Flow as a wire tap, meaning that elements that pass through will also be sent to the wire-tap Sink, without the latter affecting the mainline flow.
Attaches the given Sink to this Flow as a wire tap, meaning that elements that pass through will also be sent to the wire-tap Sink, without the latter affecting the mainline flow. If the wire-tap Sink backpressures, elements that would've been sent to it will be dropped instead.
It is similar to #alsoTo which does backpressure instead of dropping elements.
Emits when element is available and demand exists from the downstream; the element will also be sent to the wire-tap Sink if there is demand.
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Attaches the given Sink to this Flow as a wire tap, meaning that elements that pass through will also be sent to the wire-tap Sink, without the latter affecting the mainline flow.
Attaches the given Sink to this Flow as a wire tap, meaning that elements that pass through will also be sent to the wire-tap Sink, without the latter affecting the mainline flow. If the wire-tap Sink backpressures, elements that would've been sent to it will be dropped instead.
It is similar to #alsoToMat which does backpressure instead of dropping elements.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Replace the attributes of this Source with the given ones.
Combine the elements of current Source and the given one into a stream of tuples.
Combine the elements of current Source and the given one into a stream of tuples.
Emits when all of the inputs has an element available
Backpressures when downstream backpressures
Completes when any upstream completes
Cancels when downstream cancels
Combine the elements of 2 streams into a stream of tuples, picking always the latest element of each.
Combine the elements of 2 streams into a stream of tuples, picking always the latest element of each.
A ZipLatest
has a left
and a right
input port and one out
port.
No element is emitted until at least one element from each Source becomes available.
Emits when all of the inputs have at least an element available, and then each time an element becomes * available on either of the inputs
Backpressures when downstream backpressures
Completes when any upstream completes
Cancels when downstream cancels
Combine the elements of current Source and the given one into a stream of tuples, picking always the latest element of each.
Combine the elements of current Source and the given one into a stream of tuples, picking always the latest element of each.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Combine the elements of multiple streams into a stream of combined elements using a combiner function, picking always the latest of the elements of each source.
Combine the elements of multiple streams into a stream of combined elements using a combiner function, picking always the latest of the elements of each source.
No element is emitted until at least one element from each Source becomes available. Whenever a new element appears, the zipping function is invoked with a tuple containing the new element and the other last seen elements.
Emits when all of the inputs have at least an element available, and then each time an element becomes available on either of the inputs
Backpressures when downstream backpressures
Completes when any of the upstreams completes
Cancels when downstream cancels
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function, picking always the latest of the elements of each source.
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function, picking always the latest of the elements of each source.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
Combine the elements of current Source and the given one into a stream of tuples.
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function.
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function.
Emits when all of the inputs has an element available
Backpressures when downstream backpressures
Completes when any upstream completes
Cancels when downstream cancels
Combine the elements of current Source into a stream of tuples consisting of all elements paired with their index.
Combine the elements of current Source into a stream of tuples consisting of all elements paired with their index. Indices start at 0.
Emits when upstream emits an element and is paired with their index
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function.
Put together the elements of current Source and the given one into a stream of combined elements using a combiner function.
It is recommended to use the internally optimized Keep.left
and Keep.right
combiners
where appropriate instead of manually writing functions that pass through one of the values.
If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the time between the emission of an element and the following downstream demand exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses between element emission and downstream demand.
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
If the completion of the stream does not happen until the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the completion of the stream does not happen until the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses before upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Shifts elements emission in time by a specified amount.
Shifts elements emission in time by a specified amount. It allows to store elements in internal buffer while waiting for next element to be emitted. Depending on the defined akka.stream.DelayOverflowStrategy it might drop elements or backpressure the upstream if there is no space available in the buffer.
Delay precision is 10ms to avoid unnecessary timer scheduling cycles
Internal buffer has default capacity 16. You can set buffer size by calling withAttributes(inputBuffer)
Emits when there is a pending element in the buffer and configured time for this element elapsed * EmitEarly - strategy do not wait to emit element if buffer is full
Backpressures when depending on OverflowStrategy * Backpressure - backpressures when buffer is full * DropHead, DropTail, DropBuffer - never backpressures * Fail - fails the stream if buffer gets full
Completes when upstream completes and buffered elements has been drained
Cancels when downstream cancels
time to shift all messages
Strategy that is used when incoming elements cannot fit inside the buffer
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Discard the elements received within the given duration at beginning of the stream.
Discard the elements received within the given duration at beginning of the stream.
Emits when the specified time elapsed and a new upstream element arrives
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Chunk up this stream into groups of elements received within a time window, or limited by the weight of the elements, whatever happens first.
Chunk up this stream into groups of elements received within a time window, or limited by the weight of the elements, whatever happens first. Empty groups will not be emitted if no elements are received from upstream. The last group before end-of-stream will contain the buffered elements since the previously emitted group.
Emits when the configured time elapses since the last group has been emitted or weight limit reached
Backpressures when downstream backpressures, and buffered group (+ pending element) weighs more than maxWeight
Completes when upstream completes (emits last group)
Cancels when downstream completes
maxWeight
must be positive, and d
must be greater than 0 seconds, otherwise
IllegalArgumentException is thrown.
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first.
Chunk up this stream into groups of elements received within a time window, or limited by the given number of elements, whatever happens first. Empty groups will not be emitted if no elements are received from upstream. The last group before end-of-stream will contain the buffered elements since the previously emitted group.
Emits when the configured time elapses since the last group has been emitted or n
elements is buffered
Backpressures when downstream backpressures, and there are n+1
buffered elements
Completes when upstream completes (emits last group)
Cancels when downstream completes
n
must be positive, and d
must be greater than 0 seconds, otherwise
IllegalArgumentException is thrown.
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
If the time between two processed elements exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the time between two processed elements exceeds the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException. The timeout is checked periodically, so the resolution of the check is one period (equals to timeout value).
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses between two emitted elements
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Delays the initial element by the specified duration.
Delays the initial element by the specified duration.
Emits when upstream emits an element if the initial delay is already elapsed
Backpressures when downstream backpressures or initial delay is not yet elapsed
Completes when upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
If the first element has not passed through this operator before the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
If the first element has not passed through this operator before the provided timeout, the stream is failed with a java.util.concurrent.TimeoutException.
Emits when upstream emits an element
Backpressures when downstream backpressures
Completes when upstream completes or fails if timeout elapses before first element arrives
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Injects additional elements if upstream does not emit for a configured amount of time.
Injects additional elements if upstream does not emit for a configured amount of time. In other words, this operator attempts to maintains a base rate of emitted elements towards the downstream.
If the downstream backpressures then no element is injected until downstream demand arrives. Injected elements do not accumulate during this period.
Upstream elements are always preferred over injected elements.
Emits when upstream emits an element or if the upstream was idle for the configured period
Backpressures when downstream backpressures
Completes when upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Materializes to FlowMonitor<Out>
that allows monitoring of the current flow.
Materializes to FlowMonitor<Out>
that allows monitoring of the current flow. All events are propagated
by the monitor unchanged. Note that the monitor inserts a memory barrier every time it processes an
event, and may therefor affect performance.
The combine
function is used to combine the FlowMonitor
with this flow's materialized value.
(Since version 2.5.17) Use monitor() or monitorMat(combine) instead
Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements.
Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recover
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and pf returns an element
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
(Since version 2.4.4) Use recoverWithRetries instead.
Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements.
Recover allows to send last element on failure and gracefully complete the stream Since the underlying failure signal onError arrives out-of-band, it might jump over existing elements. This operator can recover the failure signal, but not the skipped elements, which will be dropped.
Throwing an exception inside recover
_will_ be logged on ERROR level automatically.
Emits when element is available from the upstream or upstream is failed and pf returns an element
Backpressures when downstream backpressures
Completes when upstream completes or upstream failed with exception pf can handle
Cancels when downstream cancels
(Since version 2.4.4) Use recoverWithRetries instead.
Terminate processing (and cancel the upstream publisher) after the given duration.
Terminate processing (and cancel the upstream publisher) after the given duration. Due to input buffering some elements may have been requested from upstream publishers that will then not be processed downstream of this step.
Note that this can be combined with #take to limit the number of elements within the duration.
Emits when an upstream element arrives
Backpressures when downstream backpressures
Completes when upstream completes or timer fires
Cancels when downstream cancels or timer fires
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Sends elements downstream with speed limited to cost/per
.
Sends elements downstream with speed limited to cost/per
. Cost is
calculating for each element individually by calling calculateCost
function.
This operator works for streams when elements have different cost(length).
Streams of ByteString
for example.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and started.
Parameter mode
manages behavior when upstream is faster than throttle rate:
It is recommended to use non-zero burst sizes as they improve both performance and throttling precision by allowing the implementation to avoid using the scheduler when input rates fall below the enforced limit and to reduce most of the inaccuracy caused by the scheduler resolution (which is in the range of milliseconds).
WARNING: Be aware that throttle is using scheduler to slow down the stream. This scheduler has minimal time of triggering
next push. Consequently it will slow down the stream as it has minimal pause for emitting. This can happen in
case burst is 0 and speed is higher than 30 events per second. You need to increase the maximumBurst
if
elements arrive with small interval (30 milliseconds or less). Use the overloaded throttle
method without
maximumBurst
parameter to automatically calculate the maximumBurst
based on the given rate (cost/per
).
In other words the throttler always enforces the rate limit when maximumBurst
parameter is given, but in
certain cases (mostly due to limited scheduler resolution) it enforces a tighter bound than what was prescribed.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
Sends elements downstream with speed limited to elements/per
.
Sends elements downstream with speed limited to elements/per
. In other words, this operator set the maximum rate
for emitting messages. This operator works for streams where all elements have the same cost or length.
Throttle implements the token bucket model. There is a bucket with a given token capacity (burst size or maximumBurst).
Tokens drops into the bucket at a given rate and can be spared
for later use up to bucket capacity
to allow some burstiness. Whenever stream wants to send an element, it takes as many
tokens from the bucket as element costs. If there isn't any, throttle waits until the
bucket accumulates enough tokens. Elements that costs more than the allowed burst will be delayed proportionally
to their cost minus available tokens, meeting the target rate. Bucket is full when stream just materialized and started.
Parameter mode
manages behavior when upstream is faster than throttle rate:
It is recommended to use non-zero burst sizes as they improve both performance and throttling precision by allowing the implementation to avoid using the scheduler when input rates fall below the enforced limit and to reduce most of the inaccuracy caused by the scheduler resolution (which is in the range of milliseconds).
WARNING: Be aware that throttle is using scheduler to slow down the stream. This scheduler has minimal time of triggering
next push. Consequently it will slow down the stream as it has minimal pause for emitting. This can happen in
case burst is 0 and speed is higher than 30 events per second. You need to increase the maximumBurst
if
elements arrive with small interval (30 milliseconds or less). Use the overloaded throttle
method without
maximumBurst
parameter to automatically calculate the maximumBurst
based on the given rate (cost/per
).
In other words the throttler always enforces the rate limit when maximumBurst
parameter is given, but in
certain cases (mostly due to limited scheduler resolution) it enforces a tighter bound than what was prescribed.
Emits when upstream emits an element and configured time per each element elapsed
Backpressures when downstream backpressures or the incoming rate is higher than the speed limit
Completes when upstream completes
Cancels when downstream cancels
(Since version 2.5.12) Use the overloaded one which accepts java.time.Duration instead.
This is a simplified version of throttle that spreads events evenly across the given time interval.
This is a simplified version of throttle that spreads events evenly across the given time interval.
Use this operator when you need just slow down a stream without worrying about exact amount of time between events.
If you want to be sure that no time interval has no more than specified number of events you need to use throttle() with maximumBurst attribute.
(Since version 2.5.12) Use throttle without maximumBurst
parameter instead.
This is a simplified version of throttle that spreads events evenly across the given time interval.
This is a simplified version of throttle that spreads events evenly across the given time interval.
Use this operator when you need just slow down a stream without worrying about exact amount of time between events.
If you want to be sure that no time interval has no more than specified number of events you need to use throttle() with maximumBurst attribute.
(Since version 2.5.12) Use throttle without maximumBurst
parameter instead.
This is a simplified version of throttle that spreads events evenly across the given time interval.
This is a simplified version of throttle that spreads events evenly across the given time interval.
Use this operator when you need just slow down a stream without worrying about exact amount of time between events.
If you want to be sure that no time interval has no more than specified number of events you need to use throttle() with maximumBurst attribute.
(Since version 2.5.12) Use throttle without maximumBurst
parameter instead.
This is a simplified version of throttle that spreads events evenly across the given time interval.
This is a simplified version of throttle that spreads events evenly across the given time interval.
Use this operator when you need just slow down a stream without worrying about exact amount of time between events.
If you want to be sure that no time interval has no more than specified number of events you need to use throttle() with maximumBurst attribute.
(Since version 2.5.12) Use throttle without maximumBurst
parameter instead.
Java API
A
Source
is a set of stream processing steps that has one open output and an attached input. Can be used as aPublisher