content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.service.web;
  
  import alluxio.master.MasterProcess;
  import alluxio.master.service.rpc.RpcServerService;
  import alluxio.network.RejectingServer;
  
  import com.google.common.base.Preconditions;
  
  import java.net.InetSocketAddress;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.GuardedBy;
  
  /**
   * Created through {@link WebServerService.Factory}.
   * This service differs from {@link AlwaysOnWebServerService} because it deploys a web
   * server only after being promoted. It stops said web server after being demoted or stopped.
   * When a web server is not deployed, a rejecting server is deployed instead (after the service
   * has been started).
   */
  class PrimaryOnlyWebServerService extends WebServerService {
    private final InetSocketAddress mBindAddress;
    @Nullable @GuardedBy("this")
    private RejectingServer mRejectingServer = null;
  
    PrimaryOnlyWebServerService(InetSocketAddress bindAddress, MasterProcess masterProcess) {
      super(masterProcess);
      mBindAddress = bindAddress;
    }
  
    @Override
    public synchronized void start() {
      LOG.info("Starting {}", this.getClass().getSimpleName());
      startRejectingServer();
    }
  
    @Override
    public synchronized void promote() {
      LOG.info("Promoting {}", this.getClass().getSimpleName());
      stopRejectingServer();
      waitForFree();
      startWebServer();
    }
  
    @Override
    public synchronized void demote() {
      LOG.info("Demoting {}", this.getClass().getSimpleName());
      stopWebServer();
      waitForFree();
      startRejectingServer();
    }
  
    @Override
    public synchronized void stop() {
      LOG.info("Stopping {}", this.getClass().getSimpleName());
      stopWebServer();
      stopRejectingServer();
    }
  
    private synchronized void startRejectingServer() {
      Preconditions.checkState(mRejectingServer == null, "rejecting server must not be running");
      mRejectingServer = new RejectingServer(mBindAddress);
      mRejectingServer.start();
      waitForBound();
    }
  
    private synchronized void stopRejectingServer() {
      if (mRejectingServer != null) {
        mRejectingServer.stopAndJoin();
        mRejectingServer = null;
      }
    }
  
    private void waitForFree() {
      RpcServerService.waitFor(false, mBindAddress);
    }
  
    private void waitForBound() {
      RpcServerService.waitFor(true, mBindAddress);
    }
  }
  