Package org.axonframework.eventsourcing.eventstore

Interface EventStorageEngine

All Superinterfaces:

DescribableComponent

All Known Implementing Classes:

AggregateBasedAxonServerEventStorageEngine, AggregateBasedJpaEventStorageEngine, AxonServerEventStorageEngine, InMemoryEventStorageEngine

@Internal
public interface EventStorageEngine
extends DescribableComponent

Interface for providing storage engines for the StorageEngineBackedEventStore.

Provides a mechanism to

invalid reference

#appendEvents(AppendCondition, TaggedEventMessage[])

append} as well as retrieve events from an underlying storage mechanism.

Retrieval can be done either through sourcing or streaming. The former generates a finite stream intended to event source (for example) a model. The latter provides an infinite stream.

Since:

3.0

Author:

Allard Buijze, Milan Savić, Rene de Waele, Steven van Beelen

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	EventStorageEngine.AppendTransaction<R>	Interface representing the transaction of an appendEvents invocation.

Method Summary

Modifier and Type	Method	Description
CompletableFuture<EventStorageEngine.AppendTransaction<?>>	appendEvents(AppendCondition condition, ProcessingContext context, List<TaggedEventMessage<?>> events)	Appends a List of events to the underlying storage solution.
default CompletableFuture<EventStorageEngine.AppendTransaction<?>>	appendEvents(AppendCondition condition, ProcessingContext context, TaggedEventMessage<?>... events)	Append one or more events to the underlying storage solution.
CompletableFuture<TrackingToken>	firstToken()	Creates a TrackingToken that is at the first position of an event stream.
CompletableFuture<TrackingToken>	latestToken()	Creates a TrackingToken that is at the latest position of an event stream.
MessageStream<EventMessage>	source(SourcingCondition condition)	Creates a finite MessageStream of events matching the given condition.
MessageStream<EventMessage>	stream(StreamingCondition condition)	Creates an infinite MessageStream of events matching the given condition.
CompletableFuture<TrackingToken>	tokenAt(Instant at)	Creates a TrackingToken that tracks all events after the given at.

Methods inherited from interface org.axonframework.common.infra.DescribableComponent

describeTo

Method Details

appendEvents

default CompletableFuture<EventStorageEngine.AppendTransaction<?>> appendEvents(@Nonnull
 AppendCondition condition,
 @Nullable
 ProcessingContext context,
 @Nonnull
 TaggedEventMessage<?>... events)

Append one or more events to the underlying storage solution.

Events will be appended in the order that they are offered in, validating the given condition before being stored. Note that all events should have a unique event identifier. Tags paired with the events will be stored as well.

By default, this method creates a List of the offered events and then invokes

invalid reference

#appendEvents(AppendCondition, List)

.

Called during the PREPARE_COMMIT phase.

Parameters:

condition - The condition describing the transactional requirements for the append transaction

context - The current ProcessingContext, if any.

events - One or more events to append to the underlying storage solution.

Returns:

A transaction instance that can be committed or rolled back.

appendEvents

CompletableFuture<EventStorageEngine.AppendTransaction<?>> appendEvents(@Nonnull
 AppendCondition condition,
 @Nullable
 ProcessingContext context,
 @Nonnull
 List<TaggedEventMessage<?>> events)

Appends a List of events to the underlying storage solution.

Events will be appended in the order that they are offered in, validating the given condition before being stored. Note that all events should have a unique event identifier. Tags paired with the events will be stored as well.

Implementations may be able to detect conflicts during the append stage. In such case, the returned completable future will complete exceptionally, indicating such conflict. Other implementations may delay such checks until the EventStorageEngine.AppendTransaction.commit() is called.

Called during the PREPARE_COMMIT phase.

Parameters:

condition - The condition describing the transactional requirements for the append transaction

context - The current ProcessingContext, if any.

events - The List of events to append to the underlying storage solution.

Returns:

A transaction instance that can be committed or rolled back.

source

MessageStream<EventMessage> source(@Nonnull
 SourcingCondition condition)

Creates a finite MessageStream of events matching the given condition.

The final entry of the stream always contains a ConsistencyMarker in the MessageStream.Entry's resources, paired with a TerminalEventMessage. This ConsistencyMarker should be used to construct the AppendCondition when

invalid reference

appending events

.

The condition dictates the sequence to load based on the EventsCondition.criteria(). Additionally, an optional SourcingCondition.start() and

invalid reference

SourcingCondition#end()

position may be provided.

The returned stream is finite, i.e. it should not block to wait for further events if the end of the event stream of the aggregate is reached.

Parameters:

condition - The SourcingCondition dictating the stream of events to source.

Returns:

A finite MessageStream of events matching the given condition.

stream

MessageStream<EventMessage> stream(@Nonnull
 StreamingCondition condition)

Creates an infinite MessageStream of events matching the given condition.

The condition may dictate the StreamingCondition.position() to start streaming from, as well as define filter criteria for the returned MessageStream.

Parameters:

condition - The StreamingCondition dictating the StreamingCondition.position() to start streaming from, as well as the filter criteria used for the returned MessageStream.

Returns:

An infinite MessageStream of events matching the given condition.

firstToken

CompletableFuture<TrackingToken> firstToken()

Creates a TrackingToken that is at the first position of an event stream.

In other words, a token that tracks events from the beginning of time.

Returns:

A CompletableFuture of a TrackingToken at the first position of an event stream.

latestToken

CompletableFuture<TrackingToken> latestToken()

Creates a TrackingToken that is at the latest position of an event stream.

In other words, a token that tracks all new events from this point forward.

Returns:

A CompletableFuture of a TrackingToken at the latest position of an event stream.

tokenAt

CompletableFuture<TrackingToken> tokenAt(@Nonnull
 Instant at)

Creates a TrackingToken that tracks all events after the given at.

If there is an event exactly at the given at, it will be tracked too.

Parameters:

at - The Instant determining how the TrackingToken should be created. A tracking token should point to very first event before this Instant.

Returns:

A CompletableFuture of a TrackingToken at the given at, if there aren't events matching this criteria null is returned