Package org.apache.storm.starter.bolt

Class SingleJoinBolt

java.lang.Object

org.apache.storm.topology.base.BaseComponent

org.apache.storm.topology.base.BaseRichBolt

org.apache.storm.starter.bolt.SingleJoinBolt

All Implemented Interfaces:

Serializable, IBolt, IComponent, IRichBolt

public class SingleJoinBolt
extends BaseRichBolt

Example of a simple custom bolt for joining two streams. NOTE: Prefer to use the built-in JoinBolt wherever applicable

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
SingleJoinBolt(Fields outFields)

Method Summary

Modifier and Type	Method	Description
void	declareOutputFields(OutputFieldsDeclarer declarer)	Declare the output schema for all the streams of this topology.
void	execute(Tuple tuple)	Process a single tuple of input.
void	prepare(Map<String,Object> conf, TopologyContext context, OutputCollector collector)	Called when a task for this component is initialized within a worker on the cluster.

Methods inherited from class org.apache.storm.topology.base.BaseRichBolt

cleanup

Methods inherited from class org.apache.storm.topology.base.BaseComponent

getComponentConfiguration

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.storm.topology.IComponent

getComponentConfiguration

Constructor Details

SingleJoinBolt

public SingleJoinBolt(Fields outFields)

Method Details

prepare

public void prepare(Map<String,Object> conf,
 TopologyContext context,
 OutputCollector collector)

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:

conf - 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.

collector - 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.

execute

public void execute(Tuple tuple)

Description copied from interface: IBolt

Process a single tuple of input. The Tuple object contains metadata on it about which component/stream/task it came from. The values of the Tuple can be accessed using Tuple#getValue. The IBolt does not have to process the Tuple immediately. It is perfectly fine to hang onto a tuple and process it later (for instance, to do an aggregation or join).

Tuples should be emitted using the OutputCollector provided through the prepare method. It is required that all input tuples are acked or failed at some point using the OutputCollector. Otherwise, Storm will be unable to determine when tuples coming off the spouts have been completed.

For the common case of acking an input tuple at the end of the execute method, see IBasicBolt which automates this.

Parameters:

tuple - The input tuple to be processed.

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