Method newClient

src/HBaseClient.java:3736–3793

Returns a client to communicate with a Region Server. Note that this method is synchronized, so only one client at a time can be created. In practice this shouldn't be a problem as this method is not expected to be frequently called. @param host The normalized IP address of the

(final String host, final int port)

   * @return A client for this region server.
   */
  private RegionClient newClient(final String host, final int port) {
    // This big synchronized block is required because using a
    // ConcurrentHashMap wouldn't be sufficient.  We could still have 2
    // threads attempt to create the same client at the same time, and they
    // could both test the map at the same time and create 2 instances.
    final String hostport = host + ':' + port;

    RegionClient client;
    SocketChannel chan = null;
    synchronized (ip2client) {
      client = ip2client.get(hostport);
      if (client != null && client.isAlive()) {
        return client;
      }

      // We don't use Netty's ClientBootstrap class because it makes it
      // unnecessarily complicated to have control over which ChannelPipeline
      // exactly will be given to the channel.  It's over-designed.
      final RegionClientPipeline pipeline = new RegionClientPipeline();
      client = pipeline.init();
      chan = channel_factory.newChannel(pipeline);
      ip2client.put(hostport, client);  // This is guaranteed to return null.
    }
    client2regions.put(client, new ArrayList<RegionInfo>());
    num_connections_created.increment();
    // Configure and connect the channel without locking ip2client.
    final SocketChannelConfig socket_config = chan.getConfig();
    socket_config.setConnectTimeoutMillis(
        config.getInt("hbase.ipc.client.socket.timeout.connect"));
    socket_config.setTcpNoDelay(
        config.getBoolean("hbase.ipc.client.tcpnodelay"));
    // Unfortunately there is no way to override the keep-alive timeout in
    // Java since the JRE doesn't expose any way to call setsockopt() with
    // TCP_KEEPIDLE.  And of course the default timeout is >2h.  Sigh.
    socket_config.setKeepAlive(
        config.getBoolean("hbase.ipc.client.tcpkeepalive"));
    
    // socket overrides using system defaults instead of setting them in a conf
    if (config.hasProperty("hbase.ipc.client.socket.write.high_watermark")) {
      ((NioChannelConfig)config).setWriteBufferHighWaterMark(
          config.getInt("hbase.ipc.client.socket.write.high_watermark"));
    }
    if (config.hasProperty("hbase.ipc.client.socket.write.low_watermark")) {
      ((NioChannelConfig)config).setWriteBufferLowWaterMark(
          config.getInt("hbase.ipc.client.socket.write.low_watermark"));
    }
    if (config.hasProperty("hbase.ipc.client.socket.sendBufferSize")) {
      socket_config.setOption("sendBufferSize", 
          config.getInt("hbase.ipc.client.socket.sendBufferSize"));
    }
    if (config.hasProperty("hbase.ipc.client.socket.receiveBufferSize")) {
      socket_config.setOption("receiveBufferSize", 
          config.getInt("hbase.ipc.client.socket.receiveBufferSize"));
    }
    
    chan.connect(new InetSocketAddress(host, port));  // Won't block.
    return client;
  }