Package org.axonframework.eventhandling.tokenstore.inmemory

Class InMemoryTokenStore

java.lang.Object
org.axonframework.eventhandling.tokenstore.inmemory.InMemoryTokenStore
All Implemented Interfaces:
TokenStore
public class InMemoryTokenStore extends Object implements TokenStore
Implementation of a TokenStore that stores tracking tokens in memory. This implementation is thread-safe.
Author:
Rene de Waele, Christophe Bouhier

  • Constructor Details

    • InMemoryTokenStore

      public InMemoryTokenStore()
      No-arg constructor for the InMemoryTokenStore which will log a warning on initialization.

  • Method Details

    • initializeTokenSegments

      public void initializeTokenSegments(@Nonnull String processorName, int segmentCount) throws UnableToClaimTokenException
      Description copied from interface: TokenStore
      Initializes the given segmentCount number of segments for the given processorName to track its tokens. This method should only be invoked when no tokens have been stored for the given processor, yet.

      This method will initialize the tokens, 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.

      Specified by:
      initializeTokenSegments in interface TokenStore
      Parameters:
      processorName - The name of the processor to initialize segments for
      segmentCount - The number of segments to initialize
      Throws:
      UnableToClaimTokenException - when a segment has already been created

    • initializeTokenSegments

      public void initializeTokenSegments(@Nonnull String processorName, int segmentCount, TrackingToken initialToken) throws UnableToClaimTokenException
      Description copied from interface: TokenStore
      Initializes the given segmentCount number of segments for the given processorName to track its tokens. This method should only be invoked when no tokens have been stored for the given processor, yet.

      This method will store initialToken for all segments as starting point for processor, 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.

      Specified by:
      initializeTokenSegments in interface TokenStore
      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 processor
      Throws:
      UnableToClaimTokenException - when a segment has already been created

    • storeToken

      public void storeToken(TrackingToken token, @Nonnull String processorName, int segment)
      Description copied from interface: TokenStore
      Stores the given token in the store. 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.

      This method should throw an UnableToClaimTokenException when the given segment has not been initialized with a Token (albeit null) yet. In that case, a segment must have been explicitly initialized. A TokenStore implementation's ability to do so is exposed by the TokenStore.requiresExplicitSegmentInitialization() method. If that method returns false, this method may implicitly initialize a token and return that token upon invocation.

      Specified by:
      storeToken in interface TokenStore
      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
      segment - The index of the segment for which to store the token

    • fetchToken

      public TrackingToken fetchToken(@Nonnull String processorName, int segment)
      Description copied from interface: TokenStore
      Returns the last stored token for the given processorName and segment. Returns null if the stored token for the given process and segment is null.

      This method should throw an UnableToClaimTokenException when the given segment has not been initialized with a Token (albeit null) yet. In that case, a segment must have been explicitly initialized. A TokenStore implementation's ability to do so is exposed by the TokenStore.requiresExplicitSegmentInitialization() method. If that method returns false, this method may implicitly initialize a token and return that token upon invocation.

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

      Specified by:
      fetchToken in interface TokenStore
      Parameters:
      processorName - The process name for which to fetch the token
      segment - The segment index for which to fetch the token
      Returns:
      The last stored TrackingToken or null if the store holds no token for given process and segment

    • releaseClaim

      public void releaseClaim(@Nonnull String processorName, int segment)
      Description copied from interface: TokenStore
      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.

      Specified by:
      releaseClaim in interface TokenStore
      Parameters:
      processorName - The name of the process owning the token (e.g. a TrackingEventProcessor name)
      segment - the segment for which a token was obtained

    • deleteToken

      public void deleteToken(@Nonnull String processorName, int segment) throws UnableToClaimTokenException
      Description copied from interface: TokenStore
      Deletes the token for the processor with given processorName and segment. The token must be owned by the current node, to be able to delete it.

      Implementations should implement this method only when TokenStore.requiresExplicitSegmentInitialization() is overridden to return true. Deleting tokens using implementations that do not require explicit token initialization is unsafe, as a claim will automatically recreate the deleted token instance, which may result in concurrency issues.

      Specified by:
      deleteToken in interface TokenStore
      Parameters:
      processorName - The name of the processor to remove the token for
      segment - The segment to delete
      Throws:
      UnableToClaimTokenException - if the token is not currently claimed by this node

    • initializeSegment

      public void initializeSegment(TrackingToken token, @Nonnull String processorName, int segment) throws UnableToInitializeTokenException
      Description copied from interface: TokenStore
      Initializes a segment with given segment for the processor with given processorName to contain the given token.

      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 TokenStore.fetchToken(String, int) to retrieve and claim the token.

      Specified by:
      initializeSegment in interface TokenStore
      Parameters:
      token - The token to initialize the segment with
      processorName - The name of the processor to create the segment for
      segment - The identifier of the segment to initialize
      Throws:
      UnableToInitializeTokenException - if a Token already exists

    • requiresExplicitSegmentInitialization

      public boolean requiresExplicitSegmentInitialization()
      Description copied from interface: TokenStore
      Indicates whether this TokenStore instance requires segments to be explicitly initialized, before any tokens can be claimed for that segment.
      Specified by:
      requiresExplicitSegmentInitialization in interface TokenStore
      Returns:
      true if this instance requires tokens to be explicitly initialized, otherwise false.
      See Also:

    • fetchSegments

      public int[] fetchSegments(@Nonnull String processorName)
      Description copied from interface: TokenStore
      Returns an array of known segments for a given processorName.

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

      Specified by:
      fetchSegments in interface TokenStore
      Parameters:
      processorName - The process name for which to fetch the segments
      Returns:
      an array of segment identifiers.

    • retrieveStorageIdentifier

      public Optional<String> retrieveStorageIdentifier()
      Description copied from interface: TokenStore
      Returns a unique identifier that uniquely identifies the storage location of the tokens in this store. 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 TokenStore.fetchToken(String, int), TokenStore.fetchSegments(String), etc. When no Transaction is active, the behavior is undefined.

      Specified by:
      retrieveStorageIdentifier in interface TokenStore
      Returns:
      an identifier to uniquely identify the storage location of tokens in this TokenStore.