backtype.storm.topology

Class BasicBoltExecutor

java.lang.Object

backtype.storm.topology.BasicBoltExecutor

All Implemented Interfaces:

IBolt, IComponent, IRichBolt, Serializable

public class BasicBoltExecutor
extends Object
implements IRichBolt

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor and Description
BasicBoltExecutor(IBasicBolt bolt)

Method Summary

Methods

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.
void	execute(Tuple input) Process a single tuple of input.
Map<String,Object>	getComponentConfiguration() Declare configuration specific to this component.
void	prepare(Map stormConf, TopologyContext context, OutputCollector collector) Called when a task for this component is initialized within a worker on the cluster.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

public static org.slf4j.Logger LOG

Constructor Detail

BasicBoltExecutor

public BasicBoltExecutor(IBasicBolt bolt)

Method Detail

declareOutputFields

public void declareOutputFields(OutputFieldsDeclarer declarer)

Description copied from interface: IComponent

Declare the output schema for all the streams of this topology.

Specified by:

declareOutputFields in interface IComponent

Parameters:

declarer - this is used to declare output stream ids, output fields, and whether or not each output stream is a direct stream

prepare

public void prepare(Map stormConf,
           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:

Specified by:

prepare in interface IBolt

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.

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 input)

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.

Specified by:

execute in interface IBolt

Parameters:

input - The input tuple to be processed.

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.

Specified by:

cleanup in interface IBolt

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

Specified by:

getComponentConfiguration in interface IComponent