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:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.storm.topology.BaseStatefulBoltExecutor

BaseStatefulBoltExecutor.AnchoringOutputCollector

Field Summary

Fields inherited from class org.apache.storm.topology.BaseStatefulBoltExecutor

collector

Constructor Summary

Constructors

Constructor and Description
CheckpointTupleForwarder(IRichBolt bolt)

Method Summary

Modifier and Type	Method and Description
void	cleanup() Called when an IBolt is going to be shutdown.
void	declareOutputFields(OutputFieldsDeclarer declarer) Declare the output schema for all the streams of this topology.
Map<String,Object>	getComponentConfiguration() Declare configuration specific to this component.
protected void	handleCheckpoint(Tuple checkpointTuple, CheckPointState.Action action, long txid) Forwards the checkpoint tuple downstream.
protected void	handleTuple(Tuple input) Hands off tuple to the wrapped bolt to execute.
void	prepare(Map stormConf, TopologyContext context, OutputCollector outputCollector) Called when a task for this component is initialized within a worker on the cluster.

Methods inherited from class org.apache.storm.topology.BaseStatefulBoltExecutor

declareCheckpointStream, execute, init

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CheckpointTupleForwarder

public CheckpointTupleForwarder(IRichBolt bolt)

Method Detail

prepare

public void prepare(Map stormConf,
                    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:

stormConf - 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. There is no guarentee that cleanup will be called, because the supervisor kill -9’s worker processes on the cluster.

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