Package org.axonframework.messaging.eventhandling.processing.streaming.token.store

Interface TokenStore

All Known Implementing Classes:
InMemoryTokenStore, JdbcTokenStore, JpaTokenStore
public interface TokenStore
Describes a component capable of storing and retrieving event tracking tokens.

A StreamingEventProcessor that is tracking an event stream can use the store to keep track of its position in the event stream. Tokens are stored by process name and segment index, enabling the same processor to be distributed over multiple processes or machines.

Since:
3.0.0
Author:
Allard Buijze, Rene de Waele

  • Method Details

    • initializeTokenSegments

      @Nonnull CompletableFuture<List<Segment>> initializeTokenSegments(@Nonnull String processorName, int segmentCount, @Nullable TrackingToken initialToken, @Nullable ProcessingContext context)
      Initializes a given number of segments for the given processorName to track its tokens.

      Returns a CompletableFuture that completes when the segments were successfully initialized. The returned future will complete exceptionally with an UnableToClaimTokenException when a segment to be initialized already exists.

      This method should only be invoked when no tokens have been stored for the given processor, yet.

      This method will store the given initialToken for all segments as the starting point for the processor with the given processorName, but not claim them. It will create the segments ranging from 0 until segmentCount - 1.

      The exact behavior when this method is called while tokens were already present is undefined in case the token already present is not owned by the initializing process.

      Parameters:
      processorName - The name of the processor to initialize segments for.
      segmentCount - The number of segments to initialize.
      initialToken - The initial token which is used as a starting point for the processor.
      context - The processing context to use when initializing the segments, if any.
      Returns:
      A CompletableFuture that completes when the segments have been initialized

    • storeToken

      @Nonnull CompletableFuture<Void> storeToken(@Nullable TrackingToken token, @Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Stores the given token in the store.

      Returns a CompletableFuture that completes when the token was successfully stored. The returned future will complete exceptionally with an UnableToClaimTokenException if the token was not initialized, or was claimed by another process.

      The token marks the current position of the process with given processorName and segment. The given token may be null. Any claims made by the current process have their timestamp updated.

      Parameters:
      token - The token to store for a given process and segment. May be null.
      processorName - The name of the process for which to store the token.
      segmentId - The index of the segment for which to store the token.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that completes when the token has been stored.

    • fetchToken

      @Nonnull CompletableFuture<TrackingToken> fetchToken(@Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Fetches the last stored token for the given processorName and segmentId.

      Returns a CompletableFuture that completes with the fetched token, or null if the token was null. The returned future will complete exceptionally with an UnableToClaimTokenException if the token did not exist or was claimed by another process.

      The token will be claimed by the current process (JVM instance), preventing access by other instances. To release the claim, use releaseClaim(String, int, ProcessingContext)

      Parameters:
      processorName - The process name for which to fetch the token.
      segmentId - The segment index for which to fetch the token.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture with the last stored TrackingToken or null if the store holds no token for the given process and segment.

    • fetchToken

      @Nonnull default CompletableFuture<TrackingToken> fetchToken(@Nonnull String processorName, @Nonnull Segment segment, @Nullable ProcessingContext context)
      Fetches the last stored token for the given processorName and segment.

      Returns a CompletableFuture that completes with the fetched token, or null if the token was null. The returned future will complete exceptionally with an UnableToClaimTokenException if the token did not exist or was claimed by another process.

      The token will be claimed by the current process (JVM instance), preventing access by other instances. To release the claim, use releaseClaim(String, int, ProcessingContext)

      Parameters:
      processorName - The process name for which to fetch the token.
      segment - The segment for which to fetch the token.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture with the last stored token or null if the store holds no token for the given process and segment.

    • extendClaim

      @Nonnull default CompletableFuture<Void> extendClaim(@Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Extends the claim on the current token held by this node for the given processorName and segment.

      Returns a CompletableFuture that completes when the claim has been successfully extended. The returned future will complete exceptionally with an UnableToClaimTokenException if the token did not exist or was claimed by another process.

      Parameters:
      processorName - The process name for which to fetch the token.
      segmentId - The segment index for which to fetch the token.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that completes when the claim-extension has been completed.

    • releaseClaim

      @Nonnull CompletableFuture<Void> releaseClaim(@Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Release a claim of the token for given processorName and segment. If no such claim existed, nothing happens.

      The caller must ensure not to use any streams opened based on the token for which the claim is released.

      Parameters:
      processorName - The name of the process owning the token (e.g. a PooledStreamingEventProcessor name).
      segmentId - The segment for which a token was obtained.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that completes when the claim-release has been completed.

    • initializeSegment

      @Nonnull CompletableFuture<Void> initializeSegment(@Nullable TrackingToken token, @Nonnull String processorName, @Nonnull Segment segment, @Nullable ProcessingContext context)
      Initializes a segment with given segment for the processor with given processorName to contain the given token.

      Returns a CompletableFuture that completes when the token segment has been successfully initialized. The returned future will complete exceptionally with an UnableToInitializeTokenException if the token already exists.

      This method fails if a token already exists for the given processor and segment, even if that token has been claimed by the active instance. This method will not claim the initialized segment. Use fetchToken(String, int, ProcessingContext) to retrieve and claim the token.

      Parameters:
      token - The token to initialize the segment with.
      processorName - The name of the processor to create the segment for.
      segment - The segment to initialize.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that completes when the segment has been initialized.
      Throws:
      UnsupportedOperationException - If this implementation does not support explicit initialization.

    • deleteToken

      @Nonnull CompletableFuture<Void> deleteToken(@Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Deletes the token associated with the specified processorName and segmentId.

      Returns a CompletableFuture that completes when the token has been successfully deleted. The returned future will complete exceptionally with an UnableToClaimTokenException if the token is not currently claimed by this node.

      The token must be owned by the current process (JVM instance) to be able to delete it.

      Parameters:
      processorName - The name of the processor to remove the token for.
      segmentId - The segment to delete.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that completes when the token deletion is complete.
      Throws:
      UnsupportedOperationException - If this operation is not supported by this implementation.

    • fetchSegment

      @Nonnull CompletableFuture<Segment> fetchSegment(@Nonnull String processorName, int segmentId, @Nullable ProcessingContext context)
      Returns a CompletableFuture that supplies the specified Segment, or null if there was no such segment.
      Parameters:
      processorName - The process name for which to fetch the segment.
      segmentId - The segment index to fetch
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture with the segment, or null on completion

    • fetchSegments

      @Nonnull CompletableFuture<List<Segment>> fetchSegments(@Nonnull String processorName, @Nullable ProcessingContext context)
      Returns a CompletableFuture that supplies a list of known segments for a given processorName on completion.

      The segments returned are segments for which a token has been stored previously. When the TokenStore is empty, the CompletableFuture will return an empty array.

      Parameters:
      processorName - The process name for which to fetch the segments.
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture with a list of segments on completion.

    • fetchAvailableSegments

      @Nonnull CompletableFuture<List<Segment>> fetchAvailableSegments(@Nonnull String processorName, @Nullable ProcessingContext context)
      Returns a CompletableFuture supplying a List of known available Segments for a given processorName.

      A segment is considered available if it is not claimed by any other event processor.

      The segments returned are segments for which a token has been stored previously and have not been claimed by another processor. When the TokenStore is empty, an empty list is returned.

      Parameters:
      processorName - The processor's name for which to fetch the segments.
      context - The current ProcessingContext, if any.
      Returns:
      A List of available Segments for the specified processorName.

    • retrieveStorageIdentifier

      @Nonnull CompletableFuture<String> retrieveStorageIdentifier(@Nullable ProcessingContext context)
      Retrieves the storage identifier associated with this store. The returned identifier uniquely identifies the storage location for the tokens in this store.

      Returns a CompletableFuture that completes with the storage identifier associated with this store. The returned future will complete exceptionally with an UnableToRetrieveIdentifierException if the identifier could not be retrieved.

      Two token store implementations that share state must return the same identifier. Two token store implementations that do not share a location must return a different identifier (or an empty optional if identifiers are not supported).

      Note that this method may require the implementation to consult its underlying storage. Therefore, a transaction should be active when this method is called, similarly to invocations like fetchToken(String, int, ProcessingContext), fetchSegments(String, ProcessingContext), etc. When no transaction is active, the behavior is undefined.

      Parameters:
      context - The current ProcessingContext, if any.
      Returns:
      A CompletableFuture that provides an identifier to uniquely identify the storage location of tokens in this TokenStore on completion.