org.apache.flink.streaming.api.functions

Interface ProcessFunction<I,O>

Type Parameters:

I - Type of the input elements.

O - Type of the output elements.

All Superinterfaces:

Function, Serializable

All Known Implementing Classes:

RichProcessFunction

@PublicEvolving
public interface ProcessFunction<I,O>
extends Function

A function that processes elements of a stream.

The function will be called for every element in the input stream and can produce zero or more output. The function can also query the time and set timers. When reacting to the firing of set timers the function can emit yet more elements.

The function will be called for every element in the input stream and can produce zero or more output elements. Contrary to the FlatMapFunction, this function can also query the time (both event and processing) and set timers, through the provided ProcessFunction.Context. When reacting to the firing of set timers the function can directly emit a result, and/or register a timer that will trigger an action in the future.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	ProcessFunction.Context Information available in an invocation of processElement(Object, Context, Collector) or onTimer(long, OnTimerContext, Collector).
static interface	ProcessFunction.OnTimerContext Information available in an invocation of onTimer(long, OnTimerContext, Collector).

Method Summary

Methods

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

Method Detail

processElement

void processElement(I value,
                  ProcessFunction.Context ctx,
                  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

void onTimer(long timestamp,
           ProcessFunction.OnTimerContext ctx,
           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.