org.apache.flink.runtime.state.KeyedStateBackend Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.state;
import org.apache.flink.api.common.state.State;
import org.apache.flink.api.common.state.StateDescriptor;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.util.Disposable;
import java.util.stream.Stream;
/**
* A keyed state backend provides methods for managing keyed state.
*
* @param The key by which state is keyed.
*/
public interface KeyedStateBackend
extends KeyedStateFactory, PriorityQueueSetFactory, Disposable {
/**
* Sets the current key that is used for partitioned state.
* @param newKey The new current key.
*/
void setCurrentKey(K newKey);
/**
* @return Current key.
*/
K getCurrentKey();
/**
* @return Serializer of the key.
*/
TypeSerializer getKeySerializer();
/**
* Applies the provided {@link KeyedStateFunction} to the state with the provided
* {@link StateDescriptor} of all the currently active keys.
*
* @param namespace the namespace of the state.
* @param namespaceSerializer the serializer for the namespace.
* @param stateDescriptor the descriptor of the state to which the function is going to be applied.
* @param function the function to be applied to the keyed state.
*
* @param The type of the namespace.
* @param The type of the state.
*/
void applyToAllKeys(
final N namespace,
final TypeSerializer namespaceSerializer,
final StateDescriptor stateDescriptor,
final KeyedStateFunction function) throws Exception;
/**
* @return A stream of all keys for the given state and namespace. Modifications to the state during iterating
* over it keys are not supported.
* @param state State variable for which existing keys will be returned.
* @param namespace Namespace for which existing keys will be returned.
*/
Stream getKeys(String state, N namespace);
/**
* Creates or retrieves a keyed state backed by this state backend.
*
* @param namespaceSerializer The serializer used for the namespace type of the state
* @param stateDescriptor The identifier for the state. This contains name and can create a default state value.
*
* @param The type of the namespace.
* @param The type of the state.
*
* @return A new key/value state backed by this backend.
*
* @throws Exception Exceptions may occur during initialization of the state and should be forwarded.
*/
S getOrCreateKeyedState(
TypeSerializer namespaceSerializer,
StateDescriptor stateDescriptor) throws Exception;
/**
* Creates or retrieves a partitioned state backed by this state backend.
*
* TODO: NOTE: This method does a lot of work caching / retrieving states just to update the namespace.
* This method should be removed for the sake of namespaces being lazily fetched from the keyed
* state backend, or being set on the state directly.
*
* @param stateDescriptor The identifier for the state. This contains name and can create a default state value.
*
* @param The type of the namespace.
* @param The type of the state.
*
* @return A new key/value state backed by this backend.
*
* @throws Exception Exceptions may occur during initialization of the state and should be forwarded.
*/
S getPartitionedState(
N namespace,
TypeSerializer namespaceSerializer,
StateDescriptor stateDescriptor) throws Exception;
@Override
void dispose();
/** State backend will call {@link KeySelectionListener#keySelected} when key context is switched if supported. */
void registerKeySelectionListener(KeySelectionListener listener);
/**
* Stop calling listener registered in {@link #registerKeySelectionListener}.
*
* @return returns true iff listener was registered before.
*/
boolean deregisterKeySelectionListener(KeySelectionListener listener);
/** Listener is given a callback when {@link #setCurrentKey} is called (key context changes). */
@FunctionalInterface
interface KeySelectionListener {
/** Callback when key context is switched. */
void keySelected(K newKey);
}
}