Package org.apache.flink.state.api.functions

Class KeyedStateReaderFunction<K,OUT>

java.lang.Object

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

org.apache.flink.state.api.functions.KeyedStateReaderFunction<K,OUT>

Type Parameters:

K - Type of the keys

OUT - 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 KeyedStateReaderFunction<K,OUT>
extends org.apache.flink.api.common.functions.AbstractRichFunction

A function that processes keys from a restored operator

For every key readKey(Object, Context, Collector) is invoked. This can produce zero or more elements as output.

NOTE: State descriptors must be eagerly registered in open(Configuration). Any attempt to dynamically register states inside of readKey will result in a RuntimeException.

NOTE: A KeyedStateReaderFunction 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
static interface	KeyedStateReaderFunction.Context	Context that KeyedStateReaderFunction's can use for getting additional data about an input record.

Constructor Summary

Constructors

Constructor	Description
KeyedStateReaderFunction()

Method Summary

Modifier and Type	Method	Description
abstract void	open(org.apache.flink.configuration.Configuration parameters)	Initialization method for the function.
abstract void	readKey(K key, KeyedStateReaderFunction.Context ctx, org.apache.flink.util.Collector<OUT> out)	Process one key from the restored state backend.

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

close, getIterationRuntimeContext, getRuntimeContext, setRuntimeContext

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.flink.api.common.functions.RichFunction

open

Constructor Detail

KeyedStateReaderFunction

public KeyedStateReaderFunction()

Method Detail

open

public abstract void open(org.apache.flink.configuration.Configuration parameters)
                   throws Exception

Initialization method for the function. It is called before readKey(Object, Context, Collector) and thus suitable for one time setup work.

This is the only method that my register state descriptors within a KeyedStateReaderFunction.

Specified by:

open in interface org.apache.flink.api.common.functions.RichFunction

Overrides:

open in class org.apache.flink.api.common.functions.AbstractRichFunction

Throws:

Exception

readKey

public abstract void readKey(K key,
                             KeyedStateReaderFunction.Context ctx,
                             org.apache.flink.util.Collector<OUT> out)
                      throws Exception

Process one key from the restored state backend.

This function can read partitioned state from the restored state backend and output zero or more elements using the Collector parameter.

Parameters:

key - The input value.

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.