Package org.apache.storm.streams.processors

Class UpdateStateByKeyProcessor<K,V,R>

java.lang.Object
org.apache.storm.streams.processors.UpdateStateByKeyProcessor<K,V,R>
All Implemented Interfaces:
Serializable, Processor<Pair<K,V>>, StatefulProcessor<K,R>
public class UpdateStateByKeyProcessor<K,V,R> extends Object implements StatefulProcessor<K,R>
See Also:

  • Field Details

  • Constructor Details

    • UpdateStateByKeyProcessor

      public UpdateStateByKeyProcessor(StateUpdater<V,R> stateUpdater)

  • Method Details

    • initState

      public void initState(KeyValueState<K,R> keyValueState)
      Description copied from interface: StatefulProcessor
      Initialize the state of the processor with the given KeyValueState.
      Specified by:
      initState in interface StatefulProcessor<K,V>
      Parameters:
      keyValueState - the key-value state

    • execute

      protected void execute(Pair<K,V> input)
      Execute some operation on the input value. Sub classes can override this when then don't care about the source stream from where the input is received.
      Parameters:
      input - the input

    • init

      public void init(ProcessorContext context)
      Initializes the processor. This is typically invoked from the underlying storm bolt's prepare method.
      Specified by:
      init in interface Processor<T>
      Parameters:
      context - the processor context

    • execute

      public void execute(Pair<K,V> input, String streamId)
      Executes some operations on the input and possibly emits some results. Processors that do not care about the source stream should override BaseProcessor.execute(Object) instead.
      Specified by:
      execute in interface Processor<T>
      Parameters:
      input - the input to be processed
      streamId - the source stream id from where the input is received

    • punctuate

      public void punctuate(String stream)
      Punctuation marks end of a batch which can be used to compute and pass the results of one stage in the pipeline to the next. For e.g. emit the results of an aggregation.
      Specified by:
      punctuate in interface Processor<T>
      Parameters:
      stream - the stream id on which the punctuation arrived

    • finish

      protected void finish()
      This is triggered to signal the end of the current batch of values. Sub classes can override this to emit the result of a batch of values, for e.g. to emit the result of an aggregate or join operation on a batch of values. If a processor does per-value operation like filter, map etc, they can choose to ignore this.

    • mayBeForwardAggUpdate

      protected final <R> void mayBeForwardAggUpdate(Supplier<R> result)
      Forwards the result update to downstream processors. Processors that operate on a batch of tuples, like aggregation, join etc can use this to emit the partial results on each input if they are operating in non-windowed mode.
      Type Parameters:
      R - the result type
      Parameters:
      result - the result function