runtime/common/src/main/java/org/apache/nemo/runtime/common/state/StageState.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.nemo.runtime.common.state;

import org.apache.nemo.common.StateMachine;

/**
 * Represents the states and their transitions of a stage.
 * <p>
 * Maintained as simple two (INCOMPLETE, COMPLETE) states to avoid ambiguity when the tasks are in different states.
 * For example it is not clear whether a stage should be EXECUTING or SHOULD_RESTART, if one of the tasks in the stage
 * is EXECUTING, and another is SHOULD_RESTART.
 */
public final class StageState {
  private final StateMachine stateMachine;

  public StageState() {
    stateMachine = buildTaskStateMachine();
  }

  private StateMachine buildTaskStateMachine() {
    final StateMachine.Builder stateMachineBuilder = StateMachine.newBuilder();

    // Add states
    stateMachineBuilder.addState(State.INCOMPLETE, "Some tasks in this stage are not complete.");
    stateMachineBuilder.addState(State.COMPLETE, "All of this stage's tasks have completed.");

    // Add transitions
    stateMachineBuilder.addTransition(
      State.INCOMPLETE, State.INCOMPLETE, "A task in the stage needs to be retried");
    stateMachineBuilder.addTransition(State.INCOMPLETE, State.COMPLETE, "All tasks complete");
    stateMachineBuilder.addTransition(State.COMPLETE, State.INCOMPLETE,
      "Completed before, but a task in this stage should be retried");
    stateMachineBuilder.addTransition(State.COMPLETE, State.COMPLETE,
      "Completed before, but probably a cloned task has completed again");

    stateMachineBuilder.setInitialState(State.INCOMPLETE);

    return stateMachineBuilder.build();
  }

  public StateMachine getStateMachine() {
    return stateMachine;
  }

  /**
   * StageState.
   */
  public enum State {
    INCOMPLETE,
    COMPLETE
  }

  @Override
  public String toString() {
    return stateMachine.getCurrentState().toString();
  }
}