org.apache.flink.runtime.state.internal.InternalKvState Maven / Gradle / Ivy
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* 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.internal;
import org.apache.flink.api.common.state.State;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.runtime.state.StateEntry;
import java.util.Collection;
/**
* The {@code InternalKvState} is the root of the internal state type hierarchy, similar to the
* {@link State} being the root of the public API state hierarchy.
*
* The internal state classes give access to the namespace getters and setters and access to
* additional functionality, like raw value access or state merging.
*
*
The public API state hierarchy is intended to be programmed against by Flink applications. The
* internal state hierarchy holds all the auxiliary methods that are used by the runtime and not
* intended to be used by user applications. These internal methods are considered of limited use to
* users and only confusing, and are usually not regarded as stable across releases.
*
*
Each specific type in the internal state hierarchy extends the type from the public state
* hierarchy:
*
*
* State
* |
* +-------------------InternalKvState
* | |
* MergingState |
* | |
* +-----------------InternalMergingState
* | |
* +--------+------+ |
* | | |
* ReducingState ListState +-----+-----------------+
* | | | |
* +-----------+ +----------- -----------------InternalListState
* | |
* +---------InternalReducingState
*
*
* @param The type of key the state is associated to
* @param The type of the namespace
* @param The type of values kept internally in state
*/
public interface InternalKvState extends State {
/** Returns the {@link TypeSerializer} for the type of key this state is associated to. */
TypeSerializer getKeySerializer();
/** Returns the {@link TypeSerializer} for the type of namespace this state is associated to. */
TypeSerializer getNamespaceSerializer();
/** Returns the {@link TypeSerializer} for the type of value this state holds. */
TypeSerializer getValueSerializer();
/**
* Sets the current namespace, which will be used when using the state access methods.
*
* @param namespace The namespace.
*/
void setCurrentNamespace(N namespace);
/**
* Returns the serialized value for the given key and namespace.
*
* If no value is associated with key and namespace, null is returned.
*
*
TO IMPLEMENTERS: This method is called by multiple threads. Anything stateful (e.g.
* serializers) should be either duplicated or protected from undesired consequences of
* concurrent invocations.
*
* @param serializedKeyAndNamespace Serialized key and namespace
* @param safeKeySerializer A key serializer which is safe to be used even in multi-threaded
* context
* @param safeNamespaceSerializer A namespace serializer which is safe to be used even in
* multi-threaded context
* @param safeValueSerializer A value serializer which is safe to be used even in multi-threaded
* context
* @return Serialized value or null if no value is associated with the key and
* namespace.
* @throws Exception Exceptions during serialization are forwarded
*/
byte[] getSerializedValue(
final byte[] serializedKeyAndNamespace,
final TypeSerializer safeKeySerializer,
final TypeSerializer safeNamespaceSerializer,
final TypeSerializer safeValueSerializer)
throws Exception;
/**
* Get global visitor of state entries.
*
* @param recommendedMaxNumberOfReturnedRecords hint to the visitor not to exceed this number of
* returned records per {@code nextEntries} call, it can still be exceeded by some smaller
* constant.
* @return global iterator over state entries
*/
StateIncrementalVisitor getStateIncrementalVisitor(
int recommendedMaxNumberOfReturnedRecords);
/**
* The state entry visitor which supports remove and update of the last returned entries.
*
* The visitor should tolerate concurrent modifications. It might trade this tolerance for
* consistency and return duplicates or not all values (created while visiting) but always state
* values which exist and up-to-date at the moment of calling {@code nextEntries()}.
*/
interface StateIncrementalVisitor {
/**
* Whether the visitor potentially has some next entries to return from {@code
* nextEntries()}.
*/
boolean hasNext();
/**
* Return some next entries which are available at the moment.
*
* If empty collection is returned, it does not mean that the visitor is exhausted but it
* means that the visitor has done some incremental work advancing and checking internal
* data structures. The finished state of the visitor has to be checked by {@code hasNext()}
* method.
*
*
The returned collection and state values must not be changed internally (there might
* be no defensive copies in {@code nextEntries()} for performance). It has to be deeply
* copied if it is to modify, e.g. with the {@code update()} method.
*/
Collection> nextEntries();
void remove(StateEntry stateEntry);
/**
* Update the value of the last returned entry from the {@code next()} method.
*
* @throws IllegalStateException if next() has never been called yet or iteration is over.
*/
void update(StateEntry stateEntry, V newValue);
}
}