akka.persistence.query.journal.leveldb.javadsl

Class LeveldbReadJournal

java.lang.Object

akka.persistence.query.journal.leveldb.javadsl.LeveldbReadJournal

All Implemented Interfaces:

AllPersistenceIdsQuery, CurrentEventsByPersistenceIdQuery, CurrentEventsByTagQuery, CurrentEventsByTagQuery2, CurrentPersistenceIdsQuery, EventsByPersistenceIdQuery, EventsByTagQuery, EventsByTagQuery2, ReadJournal

public class LeveldbReadJournal
extends java.lang.Object
implements ReadJournal, AllPersistenceIdsQuery, CurrentPersistenceIdsQuery, EventsByPersistenceIdQuery, CurrentEventsByPersistenceIdQuery, EventsByTagQuery, EventsByTagQuery2, CurrentEventsByTagQuery, CurrentEventsByTagQuery2

Java API: ReadJournal implementation for LevelDB.

It is retrieved with:

 LeveldbReadJournal queries =
   PersistenceQuery.get(system).getReadJournalFor(LeveldbReadJournal.class, LeveldbReadJournal.Identifier());
 

Corresponding Scala API is in 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 Identifier(). See reference.conf.

Constructor Summary

Constructors

Constructor and Description
LeveldbReadJournal(LeveldbReadJournal scaladslReadJournal)

Method Summary

Modifier and Type	Method and Description
Source<java.lang.String,NotUsed>	allPersistenceIds() allPersistenceIds is used for retrieving all persistenceIds of all persistent actors.
Source<EventEnvelope,NotUsed>	currentEventsByPersistenceId(java.lang.String persistenceId, long fromSequenceNr, long toSequenceNr) Same type of query as eventsByPersistenceId(java.lang.String, long, long) but the event stream is completed immediately when it reaches the end of the "result set".
Source<EventEnvelope,NotUsed>	currentEventsByTag(java.lang.String tag, long offset) Same type of query as EventsByTagQuery.eventsByTag(java.lang.String, long) but the event stream is completed immediately when it reaches the end of the "result set".
Source<EventEnvelope2,NotUsed>	currentEventsByTag(java.lang.String tag, Offset offset) Same type of query as eventsByTag(java.lang.String, akka.persistence.query.Offset) but the event stream is completed immediately when it reaches the end of the "result set".
Source<java.lang.String,NotUsed>	currentPersistenceIds() Same type of query as allPersistenceIds() but the stream is completed immediately when it reaches the end of the "result set".
Source<EventEnvelope,NotUsed>	eventsByPersistenceId(java.lang.String persistenceId, long fromSequenceNr, long toSequenceNr) eventsByPersistenceId is used for retrieving events for a specific PersistentActor identified by persistenceId.
Source<EventEnvelope,NotUsed>	eventsByTag(java.lang.String tag, long offset) Query events that have a specific tag.
Source<EventEnvelope2,NotUsed>	eventsByTag(java.lang.String tag, Offset offset) eventsByTag is used for retrieving events that were marked with a given tag, e.g.
static java.lang.String	Identifier() The default identifier for LeveldbReadJournal to be used with PersistenceQuery.getReadJournalFor(java.lang.Class<T>, java.lang.String).

Methods inherited from class java.lang.Object

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

Constructor Detail

LeveldbReadJournal

public LeveldbReadJournal(LeveldbReadJournal scaladslReadJournal)

Method Detail

Identifier

public static final java.lang.String Identifier()

The default identifier for LeveldbReadJournal to be used with PersistenceQuery.getReadJournalFor(java.lang.Class<T>, java.lang.String).

The value is "akka.persistence.query.journal.leveldb" and corresponds to the absolute path to the read journal configuration entry.

Returns:

(undocumented)

allPersistenceIds

public Source<java.lang.String,NotUsed> allPersistenceIds()

allPersistenceIds 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.

Specified by:

allPersistenceIds in interface AllPersistenceIdsQuery

Returns:

(undocumented)

currentPersistenceIds

public Source<java.lang.String,NotUsed> currentPersistenceIds()

Same type of query as allPersistenceIds() 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.

Specified by:

currentPersistenceIds in interface CurrentPersistenceIdsQuery

Returns:

(undocumented)

eventsByPersistenceId

public Source<EventEnvelope,NotUsed> eventsByPersistenceId(java.lang.String persistenceId,
                                                           long fromSequenceNr,
                                                           long toSequenceNr)

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 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(java.lang.String, long, long).

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.

Specified by:

eventsByPersistenceId in interface EventsByPersistenceIdQuery

Parameters:

persistenceId - (undocumented)

fromSequenceNr - (undocumented)

toSequenceNr - (undocumented)

Returns:

(undocumented)

currentEventsByPersistenceId

public Source<EventEnvelope,NotUsed> currentEventsByPersistenceId(java.lang.String persistenceId,
                                                                  long fromSequenceNr,
                                                                  long toSequenceNr)

Same type of query as eventsByPersistenceId(java.lang.String, long, long) 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.

Specified by:

currentEventsByPersistenceId in interface CurrentEventsByPersistenceIdQuery

Parameters:

persistenceId - (undocumented)

fromSequenceNr - (undocumented)

toSequenceNr - (undocumented)

Returns:

(undocumented)

eventsByTag

public Source<EventEnvelope2,NotUsed> eventsByTag(java.lang.String tag,
                                                  Offset offset)

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 EventAdapter that wraps the events in a 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 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 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(java.lang.String, akka.persistence.query.Offset).

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.

Specified by:

eventsByTag in interface EventsByTagQuery2

Parameters:

tag - (undocumented)

offset - (undocumented)

Returns:

(undocumented)

eventsByTag

public Source<EventEnvelope,NotUsed> eventsByTag(java.lang.String tag,
                                                 long offset)

Description copied from interface: EventsByTagQuery

Query events that have a specific tag. A tag can for example correspond to an aggregate root type (in DDD terminology).

The consumer can keep track of its current position in the event stream by storing the offset and restart the query from a given offset after a crash/restart.

The exact meaning of the offset depends on the journal and must be documented by the read journal plugin. It may be a sequential id number that uniquely identifies the position of each event within the event stream. Distributed data stores cannot easily support those semantics and they may use a weaker meaning. For example it may be a timestamp (taken when the event was created or stored). Timestamps are not unique and not strictly ordered, since clocks on different machines may not be synchronized.

The returned event stream should be ordered by offset if possible, but this can also be difficult to fulfill for a distributed data store. The order must be documented by the read journal plugin.

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 CurrentEventsByTagQuery.currentEventsByTag(java.lang.String, long).

Specified by:

eventsByTag in interface EventsByTagQuery

Parameters:

tag - (undocumented)

offset - (undocumented)

Returns:

(undocumented)

currentEventsByTag

public Source<EventEnvelope2,NotUsed> currentEventsByTag(java.lang.String tag,
                                                         Offset offset)

Same type of query as eventsByTag(java.lang.String, akka.persistence.query.Offset) 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.

Specified by:

currentEventsByTag in interface CurrentEventsByTagQuery2

Parameters:

tag - (undocumented)

offset - (undocumented)

Returns:

(undocumented)

currentEventsByTag

public Source<EventEnvelope,NotUsed> currentEventsByTag(java.lang.String tag,
                                                        long offset)

Description copied from interface: CurrentEventsByTagQuery

Same type of query as EventsByTagQuery.eventsByTag(java.lang.String, long) 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.

Specified by:

currentEventsByTag in interface CurrentEventsByTagQuery

Parameters:

tag - (undocumented)

offset - (undocumented)

Returns:

(undocumented)