Package org.apache.flink.streaming.api.functions.source.legacy

Class StatefulSequenceSource

  • All Implemented Interfaces:
    Serializable, org.apache.flink.api.common.functions.Function, org.apache.flink.api.common.functions.RichFunction, CheckpointedFunction, ParallelSourceFunction<Long>, SourceFunction<Long>
    @Internal
public class StatefulSequenceSource
extends RichParallelSourceFunction<Long>
implements CheckpointedFunction
    Deprecated.
    This class is based on the SourceFunction API, which is due to be removed. Use the new Source API instead.
    A stateful streaming source that emits each number from a given interval exactly once, possibly in parallel.

    For the source to be re-scalable, the first time the job is run, we precompute all the elements that each of the tasks should emit and upon checkpointing, each element constitutes its own partition. When rescaling, these partitions will be randomly re-assigned to the new tasks.

    This strategy guarantees that each element will be emitted exactly-once, but elements will not necessarily be emitted in ascending order, even for the same tasks.

    NOTE: this source will be removed together with the deprecated StreamExecutionEnvironmetn#generateSequence() method.

    See Also:
    Serialized Form

    • Constructor Detail

      • StatefulSequenceSource

        public StatefulSequenceSource​(long start,
                              long end)
        Deprecated.
        Creates a source that emits all numbers from the given interval exactly once.
        Parameters:
        start - Start of the range of numbers to emit.
        end - End of the range of numbers to emit.

    • Method Detail

      • initializeState

        public void initializeState​(FunctionInitializationContext context)
                     throws Exception
        Deprecated.
        Description copied from interface: CheckpointedFunction
        This method is called when the parallel function instance is created during distributed execution. Functions typically set up their state storing data structures in this method.
        Specified by:
        initializeState in interface CheckpointedFunction
        Parameters:
        context - the context for initializing the operator
        Throws:
        Exception - Thrown, if state could not be created ot restored.

      • cancel

        public void cancel()
        Deprecated.
        Description copied from interface: SourceFunction
        Cancels the source. Most sources will have a while loop inside the SourceFunction.run(SourceContext) method. The implementation needs to ensure that the source will break out of that loop after this method is called.

        A typical pattern is to have an "volatile boolean isRunning" flag that is set to false in this method. That flag is checked in the loop condition.

        In case of an ungraceful shutdown (cancellation of the source operator, possibly for failover), the thread that calls SourceFunction.run(SourceContext) will also be interrupted) by the Flink runtime, in order to speed up the cancellation (to ensure threads exit blocking methods fast, like I/O, blocking queues, etc.). The interruption happens strictly after this method has been called, so any interruption handler can rely on the fact that this method has completed (for example to ignore exceptions that happen after cancellation).

        During graceful shutdown (for example stopping a job with a savepoint), the program must cleanly exit the SourceFunction.run(SourceContext) method soon after this method was called. The Flink runtime will NOT interrupt the source thread during graceful shutdown. Source implementors must ensure that no thread interruption happens on any thread that emits records through the SourceContext from the SourceFunction.run(SourceContext) method; otherwise the clean shutdown may fail when threads are interrupted while processing the final records.

        Because the SourceFunction cannot easily differentiate whether the shutdown should be graceful or ungraceful, we recommend that implementors refrain from interrupting any threads that interact with the SourceContext at all. You can rely on the Flink runtime to interrupt the source thread in case of ungraceful cancellation. Any additionally spawned threads that directly emit records through the SourceContext should use a shutdown method that does not rely on thread interruption.

        Specified by:
        cancel in interface SourceFunction<Long>