Package org.apache.storm.topology

Class CheckpointTupleForwarder

java.lang.Object
org.apache.storm.topology.BaseStatefulBoltExecutor
org.apache.storm.topology.CheckpointTupleForwarder
All Implemented Interfaces:
Serializable, IBolt, IComponent, IRichBolt
public class CheckpointTupleForwarder extends BaseStatefulBoltExecutor
Wraps IRichBolt and forwards checkpoint tuples in a stateful topology.

When a storm topology contains one or more IStatefulBolt all non-stateful bolts are wrapped in CheckpointTupleForwarder so that the checkpoint tuples can flow through the entire topology DAG.

See Also:

  • Constructor Details

    • CheckpointTupleForwarder

      public CheckpointTupleForwarder(IRichBolt bolt)

  • Method Details

    • prepare

      public void prepare(Map<String,Object> topoConf, TopologyContext context, OutputCollector outputCollector)
      Description copied from interface: IBolt
      Called when a task for this component is initialized within a worker on the cluster. It provides the bolt with the environment in which the bolt executes.

      This includes the:

      Parameters:
      topoConf - The Storm configuration for this bolt. This is the configuration provided to the topology merged in with cluster configuration on this machine.
      context - This object can be used to get information about this task's place within the topology, including the task id and component id of this task, input and output information, etc.
      outputCollector - The collector is used to emit tuples from this bolt. Tuples can be emitted at any time, including the prepare and cleanup methods. The collector is thread-safe and should be saved as an instance variable of this bolt object.

    • cleanup

      public void cleanup()
      Description copied from interface: IBolt
      Called when an IBolt is going to be shutdown. Storm will make a best-effort attempt to call this if the worker shutdown is orderly. The Config.SUPERVISOR_WORKER_SHUTDOWN_SLEEP_SECS setting controls how long orderly shutdown is allowed to take. There is no guarantee that cleanup will be called if shutdown is not orderly, or if the shutdown exceeds the time limit.

      The one context where cleanup is guaranteed to be called is when a topology is killed when running Storm in local mode.

    • declareOutputFields

      public void declareOutputFields(OutputFieldsDeclarer declarer)
      Description copied from interface: IComponent
      Declare the output schema for all the streams of this topology.
      Parameters:
      declarer - this is used to declare output stream ids, output fields, and whether or not each output stream is a direct stream

    • getComponentConfiguration

      public Map<String,Object> getComponentConfiguration()
      Description copied from interface: IComponent
      Declare configuration specific to this component. Only a subset of the "topology.*" configs can be overridden. The component configuration can be further overridden when constructing the topology using TopologyBuilder

    • handleCheckpoint

      protected void handleCheckpoint(Tuple checkpointTuple, CheckPointState.Action action, long txid)
      Forwards the checkpoint tuple downstream.
      Specified by:
      handleCheckpoint in class BaseStatefulBoltExecutor
      Parameters:
      checkpointTuple - the checkpoint tuple
      action - the action (prepare, commit, rollback or initstate)
      txid - the transaction id.

    • handleTuple

      protected void handleTuple(Tuple input)
      Hands off tuple to the wrapped bolt to execute.

      Right now tuples continue to get forwarded while waiting for checkpoints to arrive on other streams after checkpoint arrives on one of the streams. This can cause duplicates but still at least once.

      Specified by:
      handleTuple in class BaseStatefulBoltExecutor
      Parameters:
      input - the input tuple