content: /**
   * Copyright 2011 The Apache Software Foundation
   *
   * 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 com.alibaba.wasp.master;
  
  import com.alibaba.wasp.ServerName;
  import com.alibaba.wasp.client.WaspAdmin;
  import com.alibaba.wasp.tmpl.master.MasterStatusTmpl;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.util.FSUtils;
  
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.util.List;
  import java.util.Set;
  
  /**
   * The servlet responsible for rendering the index page of the master.
   */
  public class FMasterStatusServlet extends HttpServlet {
    private static final Log LOG = LogFactory.getLog(FMasterStatusServlet.class);
    private static final long serialVersionUID = 1L;
  
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException {
      FMaster master = (FMaster) getServletContext().getAttribute(FMaster.MASTER);
      assert master != null : "No Master in context!";
  
      Configuration conf = master.getConfiguration();
      WaspAdmin admin = new WaspAdmin(conf);
  
      List<ServerName> servers = master.getFServerManager()
          .getOnlineServersList();
      Set<ServerName> deadServers = master.getFServerManager().getDeadServers();
  
      response.setContentType("text/html");
      MasterStatusTmpl tmpl = new MasterStatusTmpl()
          .setShowAppendWarning(shouldShowAppendWarning(conf))
          .setServers(servers).setDeadServers(deadServers);
      if (request.getParameter("filter") != null)
        tmpl.setFilter(request.getParameter("filter"));
      if (request.getParameter("format") != null)
        tmpl.setFormat(request.getParameter("format"));
      tmpl.render(response.getWriter(), master, admin);
    }
  
    static boolean shouldShowAppendWarning(Configuration conf) {
      try {
        return !FSUtils.isAppendSupported(conf) && FSUtils.isHDFS(conf);
      } catch (IOException e) {
        LOG.warn("Unable to determine if append is supported", e);
        return false;
      }
    }
  }
  