Package org.apache.heron.api.bolt
Class BasicBoltExecutor
- java.lang.Object
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- org.apache.heron.api.bolt.BasicBoltExecutor
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- All Implemented Interfaces:
Serializable
,IBolt
,IRichBolt
,IComponent
,IUpdatable
public class BasicBoltExecutor extends Object implements IRichBolt, IUpdatable
- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description BasicBoltExecutor(IBasicBolt aBolt)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method 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<String,Object> heronConf, TopologyContext context, OutputCollector aCollector)
Called when a task for this component is initialized within a worker on the cluster.void
update(TopologyContext topologyContext)
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Constructor Detail
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BasicBoltExecutor
public BasicBoltExecutor(IBasicBolt aBolt)
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Method Detail
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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 interfaceIComponent
- Parameters:
declarer
- this is used to declare output stream ids, output fields, and whether or not each output stream is a direct stream
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prepare
public void prepare(Map<String,Object> heronConf, TopologyContext context, OutputCollector aCollector)
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 interfaceIBolt
- Parameters:
heronConf
- The Heron 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.aCollector
- 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.
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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, Heron 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.
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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 Heron in simulator.
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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 usingTopologyBuilder
- Specified by:
getComponentConfiguration
in interfaceIComponent
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update
public void update(TopologyContext topologyContext)
- Specified by:
update
in interfaceIUpdatable
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