content: /**
   * 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.hive.service;
  
  import org.apache.hadoop.hive.conf.HiveConf;
  
  /**
   * Service.
   *
   */
  public interface Service {
  
    /**
     * Service states
     */
    enum STATE {
      /** Constructed but not initialized */
      NOTINITED,
  
      /** Initialized but not started or stopped */
      INITED,
  
      /** started and not stopped */
      STARTED,
  
      /** stopped. No further state transitions are permitted */
      STOPPED
    }
  
    /**
     * Initialize the service.
     *
     * The transition must be from {@link STATE#NOTINITED} to {@link STATE#INITED} unless the
     * operation failed and an exception was raised.
     *
     * @param config
     *          the configuration of the service
     */
    void init(HiveConf conf);
  
  
    /**
     * Start the service.
     *
     * The transition should be from {@link STATE#INITED} to {@link STATE#STARTED} unless the
     * operation failed and an exception was raised.
     */
    void start();
  
    /**
     * Stop the service.
     *
     * This operation must be designed to complete regardless of the initial state
     * of the service, including the state of all its internal fields.
     */
    void stop();
  
    /**
     * Register an instance of the service state change events.
     *
     * @param listener
     *          a new listener
     */
    void register(ServiceStateChangeListener listener);
  
    /**
     * Unregister a previously instance of the service state change events.
     *
     * @param listener
     *          the listener to unregister.
     */
    void unregister(ServiceStateChangeListener listener);
  
    /**
     * Get the name of this service.
     *
     * @return the service name
     */
    String getName();
  
    /**
     * Get the configuration of this service.
     * This is normally not a clone and may be manipulated, though there are no
     * guarantees as to what the consequences of such actions may be
     *
     * @return the current configuration, unless a specific implementation chooses
     *         otherwise.
     */
    HiveConf getHiveConf();
  
    /**
     * Get the current service state
     *
     * @return the state of the service
     */
    STATE getServiceState();
  
    /**
     * Get the service start time
     *
     * @return the start time of the service. This will be zero if the service
     *         has not yet been started.
     */
    long getStartTime();
  
  }
  