/**
 * 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.hadoop.hdfs.server.federation.router;

import org.apache.hadoop.classification.VisibleForTesting;

import static org.apache.hadoop.util.ExitUtil.terminate;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.service.CompositeService.CompositeServiceShutdownHook;
import org.apache.hadoop.tools.fedbalance.FedBalance;
import org.apache.hadoop.util.ShutdownHookManager;
import org.apache.hadoop.util.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Tool to start the {@link Router} for Router-based federation.
 */
public final class DFSRouter {

  private static final Logger LOG = LoggerFactory.getLogger(DFSRouter.class);


  /** Usage string for help message. */
  private static final String USAGE = "Usage: hdfs dfsrouter";

  /** Priority of the Router shutdown hook. */
  public static final int SHUTDOWN_HOOK_PRIORITY = 30;


  private DFSRouter() {
    // This is just a class to trigger the Router
  }

  /**
   * Main run loop for the router.
   *
   * @param argv parameters.
   */
  public static void main(String[] argv) {
    if (DFSUtil.parseHelpArgument(argv, USAGE, System.out, true)) {
      System.exit(0);
    }

    try {
      StringUtils.startupShutdownMessage(Router.class, argv, LOG);

      Router router = new Router();

      ShutdownHookManager.get().addShutdownHook(
          new CompositeServiceShutdownHook(router), SHUTDOWN_HOOK_PRIORITY);

      Configuration conf = getConfiguration();
      router.init(conf);
      router.start();
    } catch (Throwable e) {
      LOG.error("Failed to start router", e);
      terminate(1, e);
    }
  }

  @VisibleForTesting
  static Configuration getConfiguration() {
    Configuration conf = new HdfsConfiguration();
    conf.addResource(FedBalance.FED_BALANCE_DEFAULT_XML);
    conf.addResource(FedBalance.FED_BALANCE_SITE_XML);
    return conf;
  }

}