akka.persistence.query.journal.leveldb.javadsl
Same type of query as #eventsByPersistenceId but the event stream is completed immediately when it reaches the end of the "result set".
Same type of query as #eventsByPersistenceId but the event stream is completed immediately when it reaches the end of the "result set". Events that are stored after the query is completed are not included in the event stream.
Same type of query as #eventsByTag but the event stream is completed immediately when it reaches the end of the "result set".
Same type of query as #eventsByTag but the event stream is completed immediately when it reaches the end of the "result set". Events that are stored after the query is completed are not included in the event stream.
Same type of query as #persistenceIds but the stream is completed immediately when it reaches the end of the "result set".
Same type of query as #persistenceIds but the stream is completed immediately when it reaches the end of the "result set". Persistent actors that are created after the query is completed are not included in the stream.
eventsByPersistenceId
is used for retrieving events for a specific
PersistentActor
identified by persistenceId
.
eventsByPersistenceId
is used for retrieving events for a specific
PersistentActor
identified by persistenceId
.
You can retrieve a subset of all events by specifying fromSequenceNr
and toSequenceNr
or use 0L
and Long.MaxValue
respectively to retrieve all events. Note that
the corresponding sequence number of each event is provided in the
akka.persistence.query.EventEnvelope, which makes it possible to resume the
stream at a later point from a given sequence number.
The returned event stream is ordered by sequence number, i.e. the same order as the
PersistentActor
persisted the events. The same prefix of stream elements (in same order)
are returned for multiple executions of the query, except for when events have been deleted.
The stream is not completed when it reaches the end of the currently stored events, but it continues to push new events when new events are persisted. Corresponding query that is completed when it reaches the end of the currently stored events is provided by #currentEventsByPersistenceId.
The LevelDB write journal is notifying the query side as soon as events are persisted, but for
efficiency reasons the query side retrieves the events in batches that sometimes can
be delayed up to the configured refresh-interval
.
The stream is completed with failure if there is a failure in executing the query in the backend journal.
eventsByTag
is used for retrieving events that were marked with
a given tag, e.g.
eventsByTag
is used for retrieving events that were marked with
a given tag, e.g. all events of an Aggregate Root type.
To tag events you create an akka.persistence.journal.EventAdapter that wraps the events
in a akka.persistence.journal.Tagged with the given tags
.
You can retrieve a subset of all events by specifying offset
, or use 0L
to retrieve all
events with a given tag. The offset
corresponds to an ordered sequence number for
the specific tag. Note that the corresponding offset of each event is provided in the
akka.persistence.query.EventEnvelope, which makes it possible to resume the
stream at a later point from a given offset.
In addition to the offset
the EventEnvelope
also provides persistenceId
and sequenceNr
for each event. The sequenceNr
is the sequence number for the persistent actor with the
persistenceId
that persisted the event. The persistenceId
+ sequenceNr
is an unique
identifier for the event.
The offset
is exclusive, i.e. the event with the exact same sequence number will not be included
in the returned stream. This means that you can use the offset that is returned in EventEnvelope
as the offset
parameter in a subsequent query.
The returned event stream is ordered by the offset (tag sequence number), which corresponds to the same order as the write journal stored the events. The same stream elements (in same order) are returned for multiple executions of the query. Deleted events are not deleted from the tagged event stream.
The stream is not completed when it reaches the end of the currently stored events, but it continues to push new events when new events are persisted. Corresponding query that is completed when it reaches the end of the currently stored events is provided by #currentEventsByTag.
The LevelDB write journal is notifying the query side as soon as tagged events are persisted, but for
efficiency reasons the query side retrieves the events in batches that sometimes can
be delayed up to the configured refresh-interval
.
The stream is completed with failure if there is a failure in executing the query in the backend journal.
persistenceIds
is used for retrieving all persistenceIds
of all
persistent actors.
persistenceIds
is used for retrieving all persistenceIds
of all
persistent actors.
The returned event stream is unordered and you can expect different order for multiple executions of the query.
The stream is not completed when it reaches the end of the currently used persistenceIds
,
but it continues to push new persistenceIds
when new persistent actors are created.
Corresponding query that is completed when it reaches the end of the currently
currently used persistenceIds
is provided by #currentPersistenceIds.
The LevelDB write journal is notifying the query side as soon as new persistenceIds
are
created and there is no periodic polling or batching involved in this query.
The stream is completed with failure if there is a failure in executing the query in the backend journal.
Java API: akka.persistence.query.javadsl.ReadJournal implementation for LevelDB.
It is retrieved with:
LeveldbReadJournal queries = PersistenceQuery.get(system).getReadJournalFor(LeveldbReadJournal.class, LeveldbReadJournal.Identifier());
Corresponding Scala API is in akka.persistence.query.journal.leveldb.javadsl.LeveldbReadJournal.
Configuration settings can be defined in the configuration section with the absolute path corresponding to the identifier, which is
"akka.persistence.query.journal.leveldb"
for the default LeveldbReadJournal#Identifier. Seereference.conf
.