samza-api/src/main/java/org/apache/samza/checkpoint/CheckpointManager.java

/*
 * 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.samza.checkpoint;

import java.util.HashMap;
import java.util.Map;
import org.apache.samza.container.TaskName;

/**
 * CheckpointManagers read and write {@link org.apache.samza.checkpoint.Checkpoint} to some
 * implementation-specific location.
 */
public interface CheckpointManager {
  /**
   * Creates checkpoint stream.
   */
  default void createResources() { }

  /**
   * Perform startup operations.
   */
  void start();

  /**
   * Registers this manager to write checkpoints of a specific Samza stream partition.
   * @param taskName Specific Samza taskName of which to write checkpoints for.
   */
  void register(TaskName taskName);

  /**
   * Writes a checkpoint based on the current state of a Samza stream partition.
   * @param taskName Specific Samza taskName of which to write a checkpoint of.
   * @param checkpoint Reference to a Checkpoint object to store offset data in.
   */
  void writeCheckpoint(TaskName taskName, Checkpoint checkpoint);

  /**
   * Returns the last recorded checkpoint for a specified taskName.
   * @param taskName Specific Samza taskName for which to get the last checkpoint of.
   * @return A Checkpoint object with the recorded offset data of the specified partition
   *         or null if there is no recorded checkpoints for the task.
   */
  Checkpoint readLastCheckpoint(TaskName taskName);

  /**
   * Perform teardown operations for the Manager. Checkpoints are still persisted.
   */
  void stop();

  /**
   * Clear the checkpoints in the checkpoint stream.
   */
  default void clearCheckpoints() { }

  /**
   * Returns the last recorded checkpoint for all tasks present in the implementation-specific location.
   * All tasks contains all the tasks within the current job model.
   * All tasks also includes tasks which may have been part of the job model during a previous deploy.
   * @return A Map of TaskName to Checkpoint object.
   *         The Checkpoint object has the recorded offset data of the specified partition.
   */
  default Map<TaskName, Checkpoint> readAllCheckpoints() {
    return new HashMap<>();
  };
}