The version of Apache log4j used by SoundHelix.

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PRE_UGLI_MOVE :: src / java / org / apache / log4j / net /

SocketAppender.java

/*
 * Copyright 1999,2004 The Apache Software Foundation.
 * 
 * Licensed 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.
 */


// Contributors: Dan MacDonald <dan@redknee.com>
package org.apache.log4j.net;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.LogManager;
import org.apache.log4j.helpers.Constants;
import org.apache.log4j.spi.LoggingEvent;

import java.io.IOException;
import java.io.ObjectOutputStream;

import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;


/**
        Sends {@link LoggingEvent} objects to a remote a log server,
        usually a {@link SocketNode}.

        <p>The SocketAppender has the following properties:

        <ul>

          <p><li>If sent to a {@link SocketNode}, remote logging is
          non-intrusive as far as the log event is concerned. In other
          words, the event will be logged with the same time stamp, {@link
          org.apache.log4j.NDC}, location info as if it were logged locally by
          the client.

          <p><li>SocketAppenders do not use a layout. They ship a
          serialized {@link LoggingEvent} object to the server side.

          <p><li>Remote logging uses the TCP protocol. Consequently, if
          the server is reachable, then log events will eventually arrive
          at the server.

          <p><li>If the remote server is down, the logging requests are
          simply dropped. However, if and when the server comes back up,
          then event transmission is resumed transparently. This
          transparent reconneciton is performed by a <em>connector</em>
          thread which periodically attempts to connect to the server.

          <p><li>Logging events are automatically <em>buffered</em> by the
          native TCP implementation. This means that if the link to server
          is slow but still faster than the rate of (log) event production
          by the client, the client will not be affected by the slow
          network connection. However, if the network connection is slower
          then the rate of event production, then the client can only
          progress at the network rate. In particular, if the network link
          to the the server is down, the client will be blocked.

          <p>On the other hand, if the network link is up, but the server
          is down, the client will not be blocked when making log requests
          but the log events will be lost due to server unavailability.

          <p><li>Even if a <code>SocketAppender</code> is no longer
          attached to any category, it will not be garbage collected in
          the presence of a connector thread. A connector thread exists
          only if the connection to the server is down. To avoid this
          garbage collection problem, you should {@link #close} the the
          <code>SocketAppender</code> explicitly. See also next item.

          <p>Long lived applications which create/destroy many
          <code>SocketAppender</code> instances should be aware of this
          garbage collection problem. Most other applications can safely
          ignore it.

          <p><li>If the JVM hosting the <code>SocketAppender</code> exits
          before the <code>SocketAppender</code> is closed either
          explicitly or subsequent to garbage collection, then there might
          be untransmitted data in the pipe which might be lost. This is a
          common problem on Windows based systems.

          <p>To avoid lost data, it is usually sufficient to {@link
          #close} the <code>SocketAppender</code> either explicitly or by
          calling the {@link org.apache.log4j.LogManager#shutdown} method
          before exiting the application.


         </ul>

        @author  Ceki G&uuml;lc&uuml;
        @since 0.8.4 */
public class SocketAppender extends AppenderSkeleton {
  /**
   * The default port number of remote logging server (4560).
   */
  public static final int DEFAULT_PORT = 4560;

  /**
   * The default reconnection delay (30000 milliseconds or 30 seconds).
   */
  static final int DEFAULT_RECONNECTION_DELAY = 30000;

  // reset the ObjectOutputStream every 70 calls
  //private static final int RESET_FREQUENCY = 70;
  private static final int RESET_FREQUENCY = 1;

  /**
   * We remember host name as String in addition to the resolved
   * InetAddress so that it can be returned via getOption().
   */
  String remoteHost;
  InetAddress address;
  int port = DEFAULT_PORT;
  ObjectOutputStream oos;
  int reconnectionDelay = DEFAULT_RECONNECTION_DELAY;
  boolean locationInfo = false;
  private Connector connector;
  int counter = 0;
  String hostname;
  String application;

  public SocketAppender() {
  }

  /**
         Connects to remote server at <code>address</code> and <code>port</code>.
  */
  public SocketAppender(InetAddress address, int port) {
    this.address = address;
    this.remoteHost = address.getHostName();
    this.port = port;
    connect(address, port);
  }

  /**
         Connects to remote server at <code>host</code> and <code>port</code>.
  */
  public SocketAppender(String host, int port) {
    this.port = port;
    this.address = getAddressByName(host);
    this.remoteHost = host;
    connect(address, port);
  }

  /**
         Connect to the specified <b>RemoteHost</b> and <b>Port</b>.
  */
  public void activateOptions() {
    try {
      hostname = InetAddress.getLocalHost().getHostName();
    } catch (UnknownHostException uhe) {
      try {
        hostname = InetAddress.getLocalHost().getHostAddress();
      } catch (UnknownHostException uhe2) {
        hostname = "unknown";
      }
    }

    connect(address, port);
  }

  /**
   * Close this appender.
   *
   * <p>This will mark the appender as closed and call then {@link
   * #cleanUp} method.
   * */
  public synchronized void close() {
    if (closed) {
      return;
    }

    this.closed = true;
    cleanUp();
  }

  /**
   * Drop the connection to the remote host and release the underlying
   * connector thread if it has been created
   * */
  public void cleanUp() {
    if (oos != null) {
      try {
        oos.close();
      } catch (IOException e) {
        getLogger().error("Could not close oos.", e);
      }

      oos = null;
    }

    if (connector != null) {
      //LogLog.debug("Interrupting the connector.");
      connector.interrupted = true;
      connector = null; // allow gc
    }
  }

  void connect(InetAddress address, int port) {
    if (this.address == null) {
      return;
    }

    try {
      // First, close the previous connection if any.
      cleanUp();
      oos =
        new ObjectOutputStream(new Socket(address, port).getOutputStream());
    } catch (IOException e) {
      String msg =
        "Could not connect to remote log4j server at ["
        + address.getHostName() + "].";

      if (reconnectionDelay > 0) {
        msg += " We will try again later.";
        fireConnector(); // fire the connector thread
      }

      /**
       * Rather than log an ugly stack trace, output the msg
       */
      getLogger().error(msg + "(" + e.getMessage() + ")");
    }
  }

  public void append(LoggingEvent event) {
    if (event == null) {
      return;
    }

    if (address == null) {
      errorHandler.error(
        "No remote host is set for SocketAppender named \"" + this.name
        + "\".");

      return;
    }

    if (oos != null) {
      try {
        if (locationInfo) {
          event.getLocationInformation();
        }

        if (hostname != null) {
          event.setProperty(Constants.HOSTNAME_KEY, hostname);
        }

        if (application != null) {
          event.setProperty(Constants.APPLICATION_KEY, application);
        }

        oos.writeObject(event);

        //LogLog.debug("=========Flushing.");
        oos.flush();

        if (++counter >= RESET_FREQUENCY) {
          counter = 0;

          // Failing to reset the object output stream every now and
          // then creates a serious memory leak.
          //System.err.println("Doing oos.reset()");
          oos.reset();
        }
      } catch (IOException e) {
        oos = null;
        getLogger().warn("Detected problem with connection: " + e);

        if (reconnectionDelay > 0) {
          fireConnector();
        }
      }
    }
  }

  void fireConnector() {
    if (connector == null) {
      getLogger().debug("Starting a new connector thread.");
      connector = new Connector();
      connector.setDaemon(true);
      connector.setPriority(Thread.MIN_PRIORITY);
      connector.start();
    }
  }

  static InetAddress getAddressByName(String host) {
    try {
      return InetAddress.getByName(host);
    } catch (Exception e) {
      LogManager.getLogger(SocketAppender.class).error("Could not find address of [" + host + "].", e);

      return null;
    }
  }

  /**
   * The SocketAppender does not use a layout. Hence, this method
   * returns <code>false</code>.
   * */
  public boolean requiresLayout() {
    return false;
  }

  /**
   * The <b>RemoteHost</b> option takes a string value which should be
   * the host name of the server where a {@link SocketNode} is
   * running.
   * */
  public void setRemoteHost(String host) {
    address = getAddressByName(host);
    remoteHost = host;
  }

  /**
         Returns value of the <b>RemoteHost</b> option.
   */
  public String getRemoteHost() {
    return remoteHost;
  }

  /**
         The <b>Port</b> option takes a positive integer representing
         the port where the server is waiting for connections.
   */
  public void setPort(int port) {
    this.port = port;
  }

  /**
         Returns value of the <b>Port</b> option.
   */
  public int getPort() {
    return port;
  }

  /**
         The <b>LocationInfo</b> option takes a boolean value. If true,
         the information sent to the remote host will include location
         information. By default no location information is sent to the server.
   */
  public void setLocationInfo(boolean locationInfo) {
    this.locationInfo = locationInfo;
  }

  /**
         Returns value of the <b>LocationInfo</b> option.
   */
  public boolean getLocationInfo() {
    return locationInfo;
  }

  /**
         * The <b>App</b> option takes a string value which should be the
         * name of the application getting logged
         * If property was already set (via system property), don't set here.
   */
  public void setApplication(String lapp) {
    this.application = lapp;
  }

  /**
   *  Returns value of the <b>Application</b> option.
   */
  public String getApplication() {
    return application;
  }

  /**
         The <b>ReconnectionDelay</b> option takes a positive integer
         representing the number of milliseconds to wait between each
         failed connection attempt to the server. The default value of
         this option is 30000 which corresponds to 30 seconds.

         <p>Setting this option to zero turns off reconnection
         capability.
   */
  public void setReconnectionDelay(int delay) {
    this.reconnectionDelay = delay;
  }

  /**
         Returns value of the <b>ReconnectionDelay</b> option.
   */
  public int getReconnectionDelay() {
    return reconnectionDelay;
  }

  /**
         The Connector will reconnect when the server becomes available
         again.  It does this by attempting to open a new connection every
         <code>reconnectionDelay</code> milliseconds.

         <p>It stops trying whenever a connection is established. It will
         restart to try reconnect to the server when previpously open
         connection is droppped.

         @author  Ceki G&uuml;lc&uuml;
         @since 0.8.4
  */
  class Connector extends Thread {
    boolean interrupted = false;

    public void run() {
      Socket socket;

      while (!interrupted) {
        try {
          sleep(reconnectionDelay);
          getLogger().debug("Attempting connection to {}", address.getHostName());
          socket = new Socket(address, port);

          synchronized (this) {
            oos = new ObjectOutputStream(socket.getOutputStream());
            connector = null;
            getLogger().debug("Connection established. Exiting connector thread.");

            break;
          }
        } catch (InterruptedException e) {
          getLogger().debug("Connector interrupted. Leaving loop.");

          return;
        } catch (java.net.ConnectException e) {
          getLogger().debug(
            "Remote host " + address.getHostName() + " refused connection.");
        } catch (IOException e) {
          getLogger().debug(
            "Could not connect to {}. Exception is {}", address.getHostName(), e);
        }
      }

      //LogLog.debug("Exiting Connector.run() method.");
    }

    /**
       public
       void finalize() {
       LogLog.debug("Connector finalize() has been called.");
       }
    */
  }
}
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