Package org.apache.flink.runtime.state

Class SnapshotResult<T extends StateObject>

java.lang.Object
org.apache.flink.runtime.state.SnapshotResult<T>
All Implemented Interfaces:
Serializable, StateObject
public class SnapshotResult<T extends StateObject> extends Object implements StateObject
This class contains the combined results from the snapshot of a state backend:
  • A state object representing the state that will be reported to the Job Manager to acknowledge the checkpoint.
  • A state object that represents the state for the TaskLocalStateStoreImpl.
Both state objects are optional and can be null, e.g. if there was no state to snapshot in the backend. A local state object that is not null also requires a state to report to the job manager that is not null, because the Job Manager always owns the ground truth about the checkpointed state.
See Also:

  • Method Details

    • getJobManagerOwnedSnapshot

      @Nullable public T getJobManagerOwnedSnapshot()

    • getTaskLocalSnapshot

      @Nullable public T getTaskLocalSnapshot()

    • discardState

      public void discardState() throws Exception
      Description copied from interface: StateObject
      Discards the state referred to and solemnly owned by this handle, to free up resources in the persistent storage. This method is called when the state represented by this object will not be used anymore.
      Specified by:
      discardState in interface StateObject
      Throws:
      Exception

    • getStateSize

      public long getStateSize()
      Description copied from interface: StateObject
      Returns the size of the state in bytes. If the size is not known, this method should return 0.

      The values produced by this method are only used for informational purposes and for metrics/monitoring. If this method returns wrong values, the checkpoints and recovery will still behave correctly. However, efficiency may be impacted (wrong space pre-allocation) and functionality that depends on metrics (like monitoring) will be impacted.

      Note for implementors: This method should not perform any I/O operations while obtaining the state size (hence it does not declare throwing an IOException). Instead, the state size should be stored in the state object, or should be computable from the state stored in this object. The reason is that this method is called frequently by several parts of the checkpointing and issuing I/O requests from this method accumulates a heavy I/O load on the storage system at higher scale.

      Specified by:
      getStateSize in interface StateObject
      Returns:
      Size of the state in bytes.

    • empty

      public static <T extends StateObject> SnapshotResult<T> empty()

    • of

      public static <T extends StateObject> SnapshotResult<T> of(@Nullable T jobManagerState)

    • withLocalState

      public static <T extends StateObject> SnapshotResult<T> withLocalState(@Nonnull T jobManagerState, @Nonnull T localState)