org.apache.flink.datastream.api.function

Interface ProcessFunction

All Superinterfaces:

Function, Serializable

All Known Subinterfaces:

OneInputStreamProcessFunction<IN,OUT>, TwoInputBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoInputNonBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoOutputStreamProcessFunction<IN,OUT1,OUT2>

@Experimental
public interface ProcessFunction
extends Function

Base class for all user defined process functions.

Method Summary

Modifier and Type	Method and Description
default void	close() Tear-down method for the user code.
default void	open() Initialization method for the function.
default Set<StateDeclaration>	usesStates() Explicitly declares states upfront.

Method Detail

open

default void open()
           throws Exception

Initialization method for the function. It is called before the actual working methods (like processRecord) and thus suitable for one time setup work.

By default, this method does nothing.

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.

usesStates

default Set<StateDeclaration> usesStates()

Explicitly declares states upfront. Each specific state must be declared in this method before it can be used.

Returns:

all declared states used by this process function.

close

default void close()
            throws Exception

Tear-down method for the user code. It is called after the last call to the main working methods (e.g. processRecord).

This method can be used for clean up work.

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.