org.apache.storm.kafka

Class KafkaSpout

java.lang.Object

org.apache.storm.topology.base.BaseComponent

org.apache.storm.topology.base.BaseRichSpout

org.apache.storm.kafka.KafkaSpout

All Implemented Interfaces:

java.io.Serializable, ISpout, IComponent, IRichSpout

public class KafkaSpout
extends BaseRichSpout

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
KafkaSpout(SpoutConfig spoutConf)

Method Summary

Modifier and Type	Method and Description
void	ack(java.lang.Object msgId) Storm has determined that the tuple emitted by this spout with the msgId identifier has been fully processed.
void	close() Called when an ISpout is going to be shutdown.
void	deactivate() Called when a spout has been deactivated.
void	declareOutputFields(OutputFieldsDeclarer declarer) Declare the output schema for all the streams of this topology.
void	fail(java.lang.Object msgId) The tuple emitted by this spout with the msgId identifier has failed to be fully processed.
java.util.Map<java.lang.String,java.lang.Object>	getComponentConfiguration() Declare configuration specific to this component.
void	nextTuple() When this method is called, Storm is requesting that the Spout emit tuples to the output collector.
void	open(java.util.Map conf, TopologyContext context, SpoutOutputCollector aCollector) Called when a task for this component is initialized within a worker on the cluster.

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

activate

Methods inherited from class java.lang.Object

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

Constructor Detail

KafkaSpout

public KafkaSpout(SpoutConfig spoutConf)

Method Detail

open

public void open(java.util.Map conf,
                 TopologyContext context,
                 SpoutOutputCollector aCollector)

Description copied from interface: ISpout

Called when a task for this component is initialized within a worker on the cluster. It provides the spout with the environment in which the spout executes.

This includes the:

Parameters:

conf - The Storm configuration for this spout. 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.

aCollector - The collector is used to emit tuples from this spout. Tuples can be emitted at any time, including the open and close methods. The collector is thread-safe and should be saved as an instance variable of this spout object.

close

public void close()

Description copied from interface: ISpout

Called when an ISpout is going to be shutdown. There is no guarentee that close will be called, because the supervisor kill -9's worker processes on the cluster.

The one context where close is guaranteed to be called is a topology is killed when running Storm in simulator.

Specified by:

close in interface ISpout

Overrides:

close in class BaseRichSpout

nextTuple

public void nextTuple()

Description copied from interface: ISpout

When this method is called, Storm is requesting that the Spout emit tuples to the output collector. This method should be non-blocking, so if the Spout has no tuples to emit, this method should return. nextTuple, ack, and fail are all called in a tight loop in a single thread in the spout task. When there are no tuples to emit, it is courteous to have nextTuple sleep for a short amount of time (like a single millisecond) so as not to waste too much CPU.

ack

public void ack(java.lang.Object msgId)

Description copied from interface: ISpout

Storm has determined that the tuple emitted by this spout with the msgId identifier has been fully processed. Typically, an implementation of this method will take that message off the queue and prevent it from being replayed.

Specified by:

ack in interface ISpout

Overrides:

ack in class BaseRichSpout

fail

public void fail(java.lang.Object msgId)

Description copied from interface: ISpout

The tuple emitted by this spout with the msgId identifier has failed to be fully processed. Typically, an implementation of this method will put that message back on the queue to be replayed at a later time.

Specified by:

fail in interface ISpout

Overrides:

fail in class BaseRichSpout

deactivate

public void deactivate()

Description copied from interface: ISpout

Called when a spout has been deactivated. nextTuple will not be called while a spout is deactivated. The spout may or may not be reactivated in the future.

Specified by:

deactivate in interface ISpout

Overrides:

deactivate in class BaseRichSpout

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 java.util.Map<java.lang.String,java.lang.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

Overrides:

getComponentConfiguration in class BaseComponent