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.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.master.AlluxioMasterProcess;
  import alluxio.master.MasterProcess;
  import alluxio.master.service.SimpleService;
  import alluxio.web.WebServer;
  
  import com.google.common.base.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.net.InetSocketAddress;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.GuardedBy;
  
  /**
   * Defines common interface for the two difference web server behavior.
   */
  public abstract class WebServerService implements SimpleService {
    protected static final Logger LOG = LoggerFactory.getLogger(WebServerService.class);
  
    private final MasterProcess mMasterProcess;
  
    @Nullable @GuardedBy("this")
    private WebServer mWebServer = null;
  
    protected WebServerService(MasterProcess masterProcess) {
      mMasterProcess = masterProcess;
    }
  
    /**
     * @return whether the web server is serving or not
     */
    public synchronized boolean isServing() {
      return mWebServer != null && mWebServer.getServer().isRunning();
    }
  
    protected synchronized void startWebServer() {
      LOG.info("Starting web server.");
      Preconditions.checkState(mWebServer == null, "web server must not already exist");
      mWebServer = mMasterProcess.createWebServer();
      mWebServer.start();
    }
  
    protected synchronized void stopWebServer() {
      LOG.info("Stopping web server.");
      if (mWebServer != null) {
        try {
          mWebServer.stop();
        } catch (Exception e) {
          LOG.warn("Failed to stop web server", e);
        }
        mWebServer = null;
      }
    }
  
    /**
     * Factory for WebServer service.
     */
    public static class Factory {
      /**
       * @param bindAddress the address the web server will bind to
       * @param masterProcess the master process referenced inside the web server
       * @return a {@link WebServerService} that behaves according to
       * {@link alluxio.conf.PropertyKey#STANDBY_MASTER_WEB_ENABLED}
       */
      public static WebServerService create(InetSocketAddress bindAddress,
          MasterProcess masterProcess) {
        if (masterProcess instanceof AlluxioMasterProcess
            && Configuration.getBoolean(PropertyKey.STANDBY_MASTER_WEB_ENABLED)) {
          return new AlwaysOnWebServerService(masterProcess);
        }
        return new PrimaryOnlyWebServerService(bindAddress, masterProcess);
      }
    }
  }
  