org.apache.flink.runtime.state.CheckpointStorageWorkerView 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 java.io.IOException;
/**
* This interface implements the durable storage of checkpoint data and metadata streams.
* An individual checkpoint or savepoint is stored to a {@link CheckpointStorageLocation}
* which created by {@link CheckpointStorageCoordinatorView}.
*
* Methods of this interface act as a worker role in task manager.
*/
public interface CheckpointStorageWorkerView {
/**
* Resolves a storage location reference into a CheckpointStreamFactory.
*
*
The reference may be the {@link CheckpointStorageLocationReference#isDefaultReference() default reference},
* in which case the method should return the default location, taking existing configuration
* and checkpoint ID into account.
*
* @param checkpointId The ID of the checkpoint that the location is initialized for.
* @param reference The checkpoint location reference.
*
* @return A checkpoint storage location reflecting the reference and checkpoint ID.
*
* @throws IOException Thrown, if the storage location cannot be initialized from the reference.
*/
CheckpointStreamFactory resolveCheckpointStorageLocation(
long checkpointId,
CheckpointStorageLocationReference reference) throws IOException;
/**
* Opens a stream to persist checkpoint state data that is owned strictly by tasks and
* not attached to the life cycle of a specific checkpoint.
*
*
This method should be used when the persisted data cannot be immediately dropped once
* the checkpoint that created it is dropped. Examples are write-ahead-logs.
* For those, the state can only be dropped once the data has been moved to the target system,
* which may sometimes take longer than one checkpoint (if the target system is temporarily unable
* to keep up).
*
*
The fact that the job manager does not own the life cycle of this type of state means also
* that it is strictly the responsibility of the tasks to handle the cleanup of this data.
*
*
Developer note: In the future, we may be able to make this a special case of "shared state",
* where the task re-emits the shared state reference as long as it needs to hold onto the
* persisted state data.
*
* @return A checkpoint state stream to the location for state owned by tasks.
* @throws IOException Thrown, if the stream cannot be opened.
*/
CheckpointStreamFactory.CheckpointStateOutputStream createTaskOwnedStateStream() throws IOException;
}