helix-core/src/main/java/org/apache/helix/controller/pipeline/Stage.java

package org.apache.helix.controller.pipeline;

/*
 * 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.
 */

import org.apache.helix.controller.stages.ClusterEvent;

/**
 * Logically independent unit in processing callbacks for cluster changes
 */
public interface Stage {

  /**
   * Initialize a stage
   * @param context
   */
  void init(StageContext context);

  /**
   * Called before process() on each callback
   */
  void preProcess();

  /**
   * Actual callback processing logic
   * @param event
   * @throws Exception
   */
  public void process(ClusterEvent event) throws Exception;

  /**
   * Called after process() on each callback
   */
  void postProcess();

  /**
   * Destruct a stage
   */
  void release();

  /**
   * Get the name of the stage
   * @return
   */
  String getStageName();
}