org.apache.flink.state.api.output

Class OperatorSubtaskStateReducer

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichGroupReduceFunction<TaggedOperatorSubtaskState,OperatorState>

org.apache.flink.state.api.output.OperatorSubtaskStateReducer

All Implemented Interfaces:

Serializable, Function, GroupReduceFunction<TaggedOperatorSubtaskState,OperatorState>, RichFunction

@Internal
public class OperatorSubtaskStateReducer
extends RichGroupReduceFunction<TaggedOperatorSubtaskState,OperatorState>

A reducer that aggregates all OperatorSubtaskState's for a particular operator into a single OperatorState.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
OperatorSubtaskStateReducer(OperatorID operatorID, int maxParallelism)

Method Summary

Modifier and Type	Method and Description
void	open(OpenContext openContext) Initialization method for the function.
void	reduce(Iterable<TaggedOperatorSubtaskState> values, Collector<OperatorState> out) The reduce method.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext

Methods inherited from class java.lang.Object

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

Constructor Detail

OperatorSubtaskStateReducer

public OperatorSubtaskStateReducer(OperatorID operatorID,
                                   int maxParallelism)

Method Detail

open

public void open(OpenContext openContext)
          throws Exception

Description copied from interface: RichFunction

Initialization method for the function. It is called before the actual working methods (like map or join) and thus suitable for one time setup work. For functions that are part of an iteration, this method will be invoked at the beginning of each iteration superstep.

The openContext object passed to the function can be used for configuration and initialization. The openContext contains some necessary information that were configured on the function in the program composition.

 public class MyFilter extends RichFilterFunction<String> {

     private String searchString;

     public void open(OpenContext openContext) {
         // initialize the value of searchString
     }

     public boolean filter(String value) {
         return value.equals(searchString);
     }
 }
 

By default, this method does nothing.

1. If you implement open(OpenContext openContext), the open(OpenContext openContext) will be invoked and the open(Configuration parameters) won't be invoked. 2. If you don't implement open(OpenContext openContext), the open(Configuration parameters) will be invoked in the default implementation of the open(OpenContext openContext).

Parameters:

openContext - The context containing information about the context in which the function is opened.

Throws:

Exception - Implementations may forward exceptions, which are caught by the runtime. When the runtime catches an exception, it aborts the task and lets the fail-over logic decide whether to retry the task execution.

reduce

public void reduce(Iterable<TaggedOperatorSubtaskState> values,
                   Collector<OperatorState> out)

Description copied from interface: GroupReduceFunction

The reduce method. The function receives one call per group of elements.

Specified by:

reduce in interface GroupReduceFunction<TaggedOperatorSubtaskState,OperatorState>

Specified by:

reduce in class RichGroupReduceFunction<TaggedOperatorSubtaskState,OperatorState>

Parameters:

values - All records that belong to the given input key.

out - The collector to hand results to.