content: /*
   * Copyright (c) 2024, Alibaba Cloud;
   * Licensed 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 com.aliyun.dataworks.migrationx.transformer.core.spark.command;
  
  import java.util.Optional;
  
  /**
   * A handle to a running Spark application.
   * <p>
   * Provides runtime information about the underlying Spark application, and actions to control it.
   *
   * @since 1.6.0
   */
  public interface SparkAppHandle {
  
      /**
       * Represents the application's state. A state can be "final", in which case it will not change after it's reached,
       * and means the application is not running anymore.
       *
       * @since 1.6.0
       */
      enum State {
          /**
           * The application has not reported back yet.
           */
          UNKNOWN(false),
          /**
           * The application has connected to the handle.
           */
          CONNECTED(false),
          /**
           * The application has been submitted to the cluster.
           */
          SUBMITTED(false),
          /**
           * The application is running.
           */
          RUNNING(false),
          /**
           * The application finished with a successful status.
           */
          FINISHED(true),
          /**
           * The application finished with a failed status.
           */
          FAILED(true),
          /**
           * The application was killed.
           */
          KILLED(true),
          /**
           * The Spark Submit JVM exited with a unknown status.
           */
          LOST(true);
  
          private final boolean isFinal;
  
          State(boolean isFinal) {
              this.isFinal = isFinal;
          }
  
          /**
           * Whether this state is a final state, meaning the application is not running anymore once it's reached.
           */
          public boolean isFinal() {
              return isFinal;
          }
      }
  
      /**
       * Adds a listener to be notified of changes to the handle's information. Listeners will be called from the thread
       * processing updates from the application, so they should avoid blocking or long-running operations.
       *
       * @param l Listener to add.
       */
      void addListener(Listener l);
  
      /**
       * Returns the current application state.
       */
      State getState();
  
      /**
       * Returns the application ID, or <code>null</code> if not yet known.
       */
      String getAppId();
  
      /**
       * Asks the application to stop. This is best-effort, since the application may fail to receive or act on the
       * command. Callers should watch for a state transition that indicates the application has really stopped.
       */
      void stop();
  
      /**
       * Tries to kill the underlying application. Implies {@link #disconnect()}. This will not send a {@link #stop()}
       * message to the application, so it's recommended that users first try to stop the application cleanly and only
       * resort to this method if that fails.
       */
      void kill();
  
      /**
       * Disconnects the handle from the application, without stopping it. After this method is called, the handle will
       * not be able to communicate with the application anymore.
       */
      void disconnect();
  
      /**
       * If the application failed due to an error, return the underlying error. If the app succeeded, this method returns
       * an empty {@link Optional}.
       */
      Optional<Throwable> getError();
  
      /**
       * Listener for updates to a handle's state. The callbacks do not receive information about what exactly has
       * changed, just that an update has occurred.
       *
       * @since 1.6.0
       */
      public interface Listener {
  
          /**
           * Callback for changes in the handle's state.
           *
           * @param handle The updated handle.
           * @see SparkAppHandle#getState()
           */
          void stateChanged(SparkAppHandle handle);
  
          /**
           * Callback for changes in any information that is not the handle's state.
           *
           * @param handle The updated handle.
           */
          void infoChanged(SparkAppHandle handle);
  
      }
  
  }
  