Package org.apache.flink.streaming.api.functions

Class ProcessFunction<I,O>

java.lang.Object

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

org.apache.flink.streaming.api.functions.ProcessFunction<I,O>

Type Parameters:

I - Type of the input elements.

O - Type of the output elements.

All Implemented Interfaces:

Serializable, org.apache.flink.api.common.functions.Function, org.apache.flink.api.common.functions.RichFunction

@PublicEvolving
public abstract class ProcessFunction<I,O>
extends org.apache.flink.api.common.functions.AbstractRichFunction

A function that processes elements of a stream.

For every element in the input stream #processElement(Object, Context, Collector) is invoked. This can produce zero or more elements as output. Implementations can also query the time and set timers through the provided ProcessFunction.Context. For firing timers #onTimer(long, OnTimerContext, Collector) will be invoked. This can again produce zero or more elements as output and register further timers.

NOTE: Access to keyed state and timers (which are also scoped to a key) is only available if the ProcessFunction is applied on a KeyedStream.

NOTE: A ProcessFunction is always a RichFunction. Therefore, access to the RuntimeContext is always available and setup and teardown methods can be implemented. See RichFunction.open(OpenContext) and RichFunction.close().

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
class	ProcessFunction.Context	Information available in an invocation of #processElement(Object, Context, Collector) or #onTimer(long, OnTimerContext, Collector).
class	ProcessFunction.OnTimerContext	Information available in an invocation of #onTimer(long, OnTimerContext, Collector).

Constructor Summary

Constructors

Constructor	Description
ProcessFunction()

Method Summary

Modifier and Type	Method	Description
void	onTimer(long timestamp, ProcessFunction.OnTimerContext ctx, org.apache.flink.util.Collector<O> out)	Called when a timer set using TimerService fires.
abstract void	processElement(I value, ProcessFunction.Context ctx, org.apache.flink.util.Collector<O> out)	Process one element from the input stream.

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

ProcessFunction

public ProcessFunction()

Method Detail

processElement

public abstract void processElement(I value,
                                    ProcessFunction.Context ctx,
                                    org.apache.flink.util.Collector<O> out)
                             throws Exception

Process one element from the input stream.

This function can output zero or more elements using the Collector parameter and also update internal state or set timers using the ProcessFunction.Context parameter.

Parameters:

value - The input value.

ctx - A ProcessFunction.Context that allows querying the timestamp of the element and getting a TimerService for registering timers and querying the time. The context is only valid during the invocation of this method, do not store it.

out - The collector for returning result values.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.

onTimer

public void onTimer(long timestamp,
                    ProcessFunction.OnTimerContext ctx,
                    org.apache.flink.util.Collector<O> out)
             throws Exception

Called when a timer set using TimerService fires.

Parameters:

timestamp - The timestamp of the firing timer.

ctx - An ProcessFunction.OnTimerContext that allows querying the timestamp of the firing timer, querying the TimeDomain of the firing timer and getting a TimerService for registering timers and querying the time. The context is only valid during the invocation of this method, do not store it.

out - The collector for returning result values.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.