Class TransformOperator<R,T>
- java.lang.Object
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- org.apache.heron.api.topology.BaseComponent
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- org.apache.heron.api.bolt.BaseRichBolt
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- org.apache.heron.streamlet.impl.operators.StreamletOperator<R,T>
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- org.apache.heron.streamlet.impl.operators.TransformOperator<R,T>
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- All Implemented Interfaces:
Serializable
,IBolt
,IRichBolt
,IComponent
,IStatefulComponent<Serializable,Serializable>
,IStreamletOperator<R,T>
,IStreamletRichOperator<R,T>
public class TransformOperator<R,T> extends StreamletOperator<R,T> implements IStatefulComponent<Serializable,Serializable>
TransformOperator is the class that implements the transform functionality. It takes in the transformFunction Function as the input. It calls the transformFunction setup/cleanup at the beginning/end of the processing. And for every tuple, it applies the transformFunction, and emits the resulting value- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class org.apache.heron.streamlet.impl.operators.StreamletOperator
collector, OUTPUT_FIELD_NAME
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Constructor Summary
Constructors Constructor Description TransformOperator(SerializableTransformer<? super R,? extends T> serializableTransformer)
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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
execute(Tuple tuple)
Process a single tuple of input.void
initState(State<Serializable,Serializable> startupState)
Initializes the state of the function or operator to that of a previous checkpoint.void
prepare(Map<String,Object> map, TopologyContext topologyContext, OutputCollector outputCollector)
Called when a task for this component is initialized within a worker on the cluster.void
preSave(String checkpointId)
This is a hook for the component to perform some actions just before the framework saves its state.-
Methods inherited from class org.apache.heron.streamlet.impl.operators.StreamletOperator
declareOutputFields
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Methods inherited from class org.apache.heron.api.topology.BaseComponent
getComponentConfiguration
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.heron.api.topology.IComponent
declareOutputFields, getComponentConfiguration
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Constructor Detail
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TransformOperator
public TransformOperator(SerializableTransformer<? super R,? extends T> serializableTransformer)
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Method Detail
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initState
public void initState(State<Serializable,Serializable> startupState)
Description copied from interface:IStatefulComponent
Initializes the state of the function or operator to that of a previous checkpoint. This method is invoked when a component is executed as part of a recovery run. In case there was prior state associated with the component, the state will be empty. Stateful Spouts/Bolts are expected to hold on to the state variable to save their internal stateNote that initialState() is called before open() or prepare().
- Specified by:
initState
in interfaceIStatefulComponent<R,T>
- Parameters:
startupState
- the previously saved state of the component.
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preSave
public void preSave(String checkpointId)
Description copied from interface:IStatefulComponent
This is a hook for the component to perform some actions just before the framework saves its state.- Specified by:
preSave
in interfaceIStatefulComponent<R,T>
- Parameters:
checkpointId
- the ID of the checkpoint
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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.
- Specified by:
cleanup
in interfaceIBolt
- Overrides:
cleanup
in classBaseRichBolt
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prepare
public void prepare(Map<String,Object> map, TopologyContext topologyContext, 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:
- Specified by:
prepare
in interfaceIBolt
- Overrides:
prepare
in classStreamletOperator<R,T>
- Parameters:
map
- The Heron configuration for this bolt. This is the configuration provided to the topology merged in with cluster configuration on this machine.topologyContext
- 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.
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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, 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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