org.apache.flink.runtime.state.KeyedStateBackend Maven / Gradle / Ivy
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* distributed with this work for additional information
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* 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,
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* 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.api.java.tuple.Tuple2;
import org.apache.flink.runtime.checkpoint.CheckpointType;
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);
/**
* @return A stream of all keys for the given state and namespace. Modifications to the state
* during iterating over it keys are not supported. Implementations go not make any ordering
* guarantees about the returned tupes. Two records with the same key or namespace may not
* be returned near each other in the stream.
* @param state State variable for which existing keys will be returned.
*/
Stream> getKeysAndNamespaces(String state);
/**
* 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);
default boolean isStateImmutableInStateBackend(CheckpointType checkpointOptions) {
return false;
}
/** 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);
}
}