001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.tools.offlineImageViewer;
019
020import com.google.common.annotations.VisibleForTesting;
021import io.netty.bootstrap.ServerBootstrap;
022import io.netty.channel.Channel;
023import io.netty.channel.ChannelInitializer;
024import io.netty.channel.ChannelPipeline;
025import io.netty.channel.EventLoopGroup;
026import io.netty.channel.group.ChannelGroup;
027import io.netty.channel.group.DefaultChannelGroup;
028import io.netty.channel.nio.NioEventLoopGroup;
029import io.netty.channel.socket.SocketChannel;
030import io.netty.channel.socket.nio.NioServerSocketChannel;
031import io.netty.handler.codec.http.HttpRequestDecoder;
032import io.netty.handler.codec.http.HttpResponseEncoder;
033import io.netty.handler.codec.string.StringEncoder;
034import io.netty.util.concurrent.GlobalEventExecutor;
035import org.apache.commons.logging.Log;
036import org.apache.commons.logging.LogFactory;
037
038import java.io.Closeable;
039import java.io.IOException;
040import java.net.InetSocketAddress;
041
042/**
043 * WebImageViewer loads a fsimage and exposes read-only WebHDFS API for its
044 * namespace.
045 */
046public class WebImageViewer implements Closeable {
047  public static final Log LOG = LogFactory.getLog(WebImageViewer.class);
048
049  private Channel channel;
050  private InetSocketAddress address;
051
052  private final ServerBootstrap bootstrap;
053  private final EventLoopGroup bossGroup;
054  private final EventLoopGroup workerGroup;
055  private final ChannelGroup allChannels;
056
057  public WebImageViewer(InetSocketAddress address) {
058    this.address = address;
059    this.bossGroup = new NioEventLoopGroup();
060    this.workerGroup = new NioEventLoopGroup();
061    this.allChannels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
062    this.bootstrap = new ServerBootstrap()
063      .group(bossGroup, workerGroup)
064      .channel(NioServerSocketChannel.class);
065  }
066
067  /**
068   * Start WebImageViewer and wait until the thread is interrupted.
069   * @param fsimage the fsimage to load.
070   * @throws IOException if failed to load the fsimage.
071   */
072  public void start(String fsimage) throws IOException {
073    try {
074      initServer(fsimage);
075      channel.closeFuture().await();
076    } catch (InterruptedException e) {
077      LOG.info("Interrupted. Stopping the WebImageViewer.");
078      close();
079    }
080  }
081
082  /**
083   * Start WebImageViewer.
084   * @param fsimage the fsimage to load.
085   * @throws IOException if fail to load the fsimage.
086   */
087  @VisibleForTesting
088  public void initServer(String fsimage)
089          throws IOException, InterruptedException {
090    final FSImageLoader loader = FSImageLoader.load(fsimage);
091
092    bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
093      @Override
094      protected void initChannel(SocketChannel ch) throws Exception {
095        ChannelPipeline p = ch.pipeline();
096        p.addLast(new HttpRequestDecoder(),
097          new StringEncoder(),
098          new HttpResponseEncoder(),
099          new FSImageHandler(loader, allChannels));
100      }
101    });
102
103    channel = bootstrap.bind(address).sync().channel();
104    allChannels.add(channel);
105
106    address = (InetSocketAddress) channel.localAddress();
107    LOG.info("WebImageViewer started. Listening on " + address.toString() + ". Press Ctrl+C to stop the viewer.");
108  }
109
110  /**
111   * Get the listening port.
112   * @return the port WebImageViewer is listening on
113   */
114  @VisibleForTesting
115  public int getPort() {
116    return address.getPort();
117  }
118
119  @Override
120  public void close() {
121    allChannels.close().awaitUninterruptibly();
122    bossGroup.shutdownGracefully();
123    workerGroup.shutdownGracefully();
124  }
125}