1. @Public
    2. public interface CheckpointedFunction {
    4.     /**
    5.      * This method is called when a snapshot for a checkpoint is requested. This acts as a hook to
    6.      * the function to ensure that all state is exposed by means previously offered through {@link
    7.      * FunctionInitializationContext} when the Function was initialized, or offered now by {@link
    8.      * FunctionSnapshotContext} itself.
    9.      *
    10.      * @param context the context for drawing a snapshot of the operator
    11.      * @throws Exception Thrown, if state could not be created ot restored.
    12.      */
    13.     void snapshotState(FunctionSnapshotContext context) throws Exception;
    15.     /**
    16.      * This method is called when the parallel function instance is created during distributed
    17.      * execution. Functions typically set up their state storing data structures in this method.
    18.      *
    19.      * @param context the context for initializing the operator
    20.      * @throws Exception Thrown, if state could not be created ot restored.
    21.      */
    22.     void initializeState(FunctionInitializationContext context) throws Exception;
    23. }