org.apache.cassandra.utils.concurrent

Class SyncFuture<V>

java.lang.Object

org.apache.cassandra.utils.concurrent.AbstractFuture<V>

org.apache.cassandra.utils.concurrent.SyncFuture<V>

Type Parameters:

V -

All Implemented Interfaces:

com.google.common.util.concurrent.ListenableFuture<V>, java.util.concurrent.Future<V>, Awaitable

Direct Known Subclasses:

SyncFutureTask, SyncPromise

public class SyncFuture<V>
extends AbstractFuture<V>

Netty's DefaultPromise uses a mutex to coordinate notifiers AND waiters between the eventLoop and the other threads. Since we register cross-thread listeners, this has the potential to block internode messaging for an unknown number of threads for an unknown period of time, if we are unlucky with the scheduler (which will certainly happen, just with some unknown but low periodicity) At the same time, we manage some other efficiencies: - We save some space when registering listeners, especially if there is only one listener, as we perform no extra allocations in this case. - We permit efficient initial state declaration, avoiding unnecessary CAS or lock acquisitions when mutating a Promise we are ourselves constructing (and can easily add more; only those we use have been added) We can also make some guarantees about our behaviour here, although we primarily mirror Netty. Specifically, we can guarantee that notifiers are always invoked in the order they are added (which may be true for netty, but was unclear and is not declared). This is useful for ensuring the correctness of some of our behaviours in OutboundConnection without having to jump through extra hoops. The implementation loosely follows that of Netty's DefaultPromise, with some slight changes; notably that we have no synchronisation on our listeners, instead using a CoW list that is cleared each time we notify listeners. We handle special values slightly differently. We do not use a special value for null, instead using a special value to indicate the result has not been set yet. This means that once isSuccess() holds, the result must be a correctly typed object (modulo generics pitfalls). All special values are also instances of FailureHolder, which simplifies a number of the logical conditions.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.cassandra.utils.concurrent.Awaitable

Awaitable.AbstractAwaitable, Awaitable.AsyncAwaitable, Awaitable.Defaults, Awaitable.SyncAwaitable

Field Summary

Fields inherited from class org.apache.cassandra.utils.concurrent.AbstractFuture

CANCELLED, UNCANCELLABLE, UNSET

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SyncFuture()
protected	SyncFuture(org.apache.cassandra.utils.concurrent.AbstractFuture.FailureHolder initialState)
protected	SyncFuture(org.apache.cassandra.utils.concurrent.AbstractFuture.FailureHolder initialState, io.netty.util.concurrent.GenericFutureListener<? extends io.netty.util.concurrent.Future<? super V>> listener)
protected	SyncFuture(io.netty.util.concurrent.GenericFutureListener<? extends io.netty.util.concurrent.Future<? super V>> listener)
protected	SyncFuture(java.lang.Throwable immediateFailure)
protected	SyncFuture(V immediateSuccess)

Method Summary

Modifier and Type	Method and Description
Future<V>	await() Wait indefinitely for this future to complete, throwing any interrupt
boolean	awaitUntil(long deadline) Await until the deadline (in nanoTime), throwing any interrupt.
<T> Future<T>	flatMap(java.util.function.Function<? super V,? extends Future<T>> flatMapper, java.util.concurrent.Executor executor) Support Futures.transformAsync(ListenableFuture, AsyncFunction, Executor) natively See AbstractFuture.addListener(GenericFutureListener) for ordering semantics.
<T> Future<T>	map(java.util.function.Function<? super V,? extends T> mapper, java.util.concurrent.Executor executor) Support Futures.transform(com.google.common.util.concurrent.ListenableFuture<I>, com.google.common.base.Function<? super I, ? extends O>, java.util.concurrent.Executor) natively See AbstractFuture.addListener(GenericFutureListener) for ordering semantics.

Methods inherited from class org.apache.cassandra.utils.concurrent.AbstractFuture

addCallback, addCallback, addCallback, addCallback, addCallback, addCallback, addListener, addListener, addListener, addListeners, await, awaitThrowUncheckedOnInterrupt, awaitThrowUncheckedOnInterrupt, awaitUninterruptibly, awaitUninterruptibly, awaitUntilThrowUncheckedOnInterrupt, awaitUntilUninterruptibly, cancel, cause, description, flatMap, get, get, getNow, getWhenDone, isCancellable, isCancelled, isDone, isSuccess, isUncancellable, map, map, notifyExecutor, removeListener, removeListeners, setUncancellable, setUncancellableExclusive, toString, tryFailure, trySuccess

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.cassandra.utils.concurrent.Future

await, awaitUninterruptibly, flatMap, rethrowIfFailed, sync, syncThrowUncheckedOnInterrupt, syncUninterruptibly

Constructor Detail

SyncFuture

protected SyncFuture()

SyncFuture

protected SyncFuture(V immediateSuccess)

SyncFuture

protected SyncFuture(java.lang.Throwable immediateFailure)

SyncFuture

protected SyncFuture(org.apache.cassandra.utils.concurrent.AbstractFuture.FailureHolder initialState)

SyncFuture

protected SyncFuture(io.netty.util.concurrent.GenericFutureListener<? extends io.netty.util.concurrent.Future<? super V>> listener)

SyncFuture

protected SyncFuture(org.apache.cassandra.utils.concurrent.AbstractFuture.FailureHolder initialState,
                     io.netty.util.concurrent.GenericFutureListener<? extends io.netty.util.concurrent.Future<? super V>> listener)

Method Detail

map

public <T> Future<T> map(java.util.function.Function<? super V,? extends T> mapper,
                         java.util.concurrent.Executor executor)

Support Futures.transform(com.google.common.util.concurrent.ListenableFuture<I>, com.google.common.base.Function<? super I, ? extends O>, java.util.concurrent.Executor) natively See AbstractFuture.addListener(GenericFutureListener) for ordering semantics.

flatMap

public <T> Future<T> flatMap(java.util.function.Function<? super V,? extends Future<T>> flatMapper,
                             @Nullable
                             java.util.concurrent.Executor executor)

Support Futures.transformAsync(ListenableFuture, AsyncFunction, Executor) natively See AbstractFuture.addListener(GenericFutureListener) for ordering semantics.

awaitUntil

public boolean awaitUntil(long deadline)
                   throws java.lang.InterruptedException

Description copied from interface: Awaitable

Await until the deadline (in nanoTime), throwing any interrupt. No spurious wakeups.

Returns:

true if we were signalled, false if the deadline elapsed

Throws:

java.lang.InterruptedException - if interrupted

await

public Future<V> await()
                throws java.lang.InterruptedException

Description copied from interface: Future

Wait indefinitely for this future to complete, throwing any interrupt

Throws:

java.lang.InterruptedException - if interrupted