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.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hive.conf.HiveConf;
  
  /**
   * ServiceOperations.
   *
   */
  public final class ServiceOperations {
    private static final Log LOG = LogFactory.getLog(AbstractService.class);
  
    private ServiceOperations() {
    }
  
    /**
     * Verify that that a service is in a given state.
     * @param state the actual state a service is in
     * @param expectedState the desired state
     * @throws IllegalStateException if the service state is different from
     * the desired state
     */
    public static void ensureCurrentState(Service.STATE state,
                                          Service.STATE expectedState) {
      if (state != expectedState) {
        throw new IllegalStateException("For this operation, the " +
                                            "current service state must be "
                                            + expectedState
                                            + " instead of " + state);
      }
    }
  
    /**
     * Initialize a service.
     * <p/>
     * The service state is checked <i>before</i> the operation begins.
     * This process is <i>not</i> thread safe.
     * @param service a service that must be in the state
     *   {@link Service.STATE#NOTINITED}
     * @param configuration the configuration to initialize the service with
     * @throws RuntimeException on a state change failure
     * @throws IllegalStateException if the service is in the wrong state
     */
  
    public static void init(Service service, HiveConf configuration) {
      Service.STATE state = service.getServiceState();
      ensureCurrentState(state, Service.STATE.NOTINITED);
      service.init(configuration);
    }
  
    /**
     * Start a service.
     * <p/>
     * The service state is checked <i>before</i> the operation begins.
     * This process is <i>not</i> thread safe.
     * @param service a service that must be in the state
     *   {@link Service.STATE#INITED}
     * @throws RuntimeException on a state change failure
     * @throws IllegalStateException if the service is in the wrong state
     */
  
    public static void start(Service service) {
      Service.STATE state = service.getServiceState();
      ensureCurrentState(state, Service.STATE.INITED);
      service.start();
    }
  
    /**
     * Initialize then start a service.
     * <p/>
     * The service state is checked <i>before</i> the operation begins.
     * This process is <i>not</i> thread safe.
     * @param service a service that must be in the state
     *   {@link Service.STATE#NOTINITED}
     * @param configuration the configuration to initialize the service with
     * @throws RuntimeException on a state change failure
     * @throws IllegalStateException if the service is in the wrong state
     */
    public static void deploy(Service service, HiveConf configuration) {
      init(service, configuration);
      start(service);
    }
  
    /**
     * Stop a service.
     * <p/>Do nothing if the service is null or not
     * in a state in which it can be/needs to be stopped.
     * <p/>
     * The service state is checked <i>before</i> the operation begins.
     * This process is <i>not</i> thread safe.
     * @param service a service or null
     */
    public static void stop(Service service) {
      if (service != null) {
        Service.STATE state = service.getServiceState();
        if (state == Service.STATE.STARTED) {
          service.stop();
        }
      }
    }
  
    /**
     * Stop a service; if it is null do nothing. Exceptions are caught and
     * logged at warn level. (but not Throwables). This operation is intended to
     * be used in cleanup operations
     *
     * @param service a service; may be null
     * @return any exception that was caught; null if none was.
     */
    public static Exception stopQuietly(Service service) {
      try {
        stop(service);
      } catch (Exception e) {
        LOG.warn("When stopping the service " + service.getName()
                     + " : " + e,
                 e);
        return e;
      }
      return null;
    }
  
  }
  