SocketAppenderBase

/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
// Contributors: Dan MacDonald <dan@redknee.com>
package ch.qos.logback.core.net;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.net.InetAddress;
import java.net.Socket;

import ch.qos.logback.core.AppenderBase;
import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.spi.PreSerializationTransformer;

/**
 *
 * This is the base class for module specific SocketAppender implementations.
 *
 * @author Ceki G&uuml;lc&uuml;
 * @author S&eacute;bastien Pennec
 */

public abstract class SocketAppenderBase<E> extends AppenderBase<E> {

  /**
   * The default port number of remote logging server (4560).
   */
  static final int DEFAULT_PORT = 4560;

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

  /**
   * We remember host name as String in addition to the resolved InetAddress so
   * that it can be returned via getOption().
   */
  protected String remoteHost;

  protected InetAddress address;
  protected int port = DEFAULT_PORT;
  protected ObjectOutputStream oos;
  protected int reconnectionDelay = DEFAULT_RECONNECTION_DELAY;

  private Connector connector;

  protected int counter = 0;

  /**
   * Start this appender.
   */
  public void start() {
    int errorCount = 0;
    if (port == 0) {
      errorCount++;
      addError("No port was configured for appender"
          + name
          + " For more information, please visit http://logback.qos.ch/codes.html#socket_no_port");
    }

    if (address == null) {
      errorCount++;
      addError("No remote address was configured for appender"
          + name
          + " For more information, please visit http://logback.qos.ch/codes.html#socket_no_host");
    }

    connect(address, port);

    if (errorCount == 0) {
      this.started = true;
    }
  }

  /**
   * Strop this appender.
   *
   * <p>
   * This will mark the appender as closed and call then {@link #cleanUp}
   * method.
   */
  @Override
  public void stop() {
    if (!isStarted())
      return;

    this.started = false;
    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) {
        addError("Could not close oos.", e);
      }
      oos = null;
    }
    if (connector != null) {
      addInfo("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 logback server at ["
          + address.getHostName() + "].";
      if (reconnectionDelay > 0) {
        msg += " We will try again later.";
        fireConnector(); // fire the connector thread
      }
      addInfo(msg, e);
    }
  }

  @Override
  protected void append(E event) {

    if (event == null)
      return;

    if (address == null) {
      addError("No remote host is set for SocketAppender named \""
          + this.name
          + "\". For more information, please visit http://logback.qos.ch/codes.html#socket_no_host");
      return;
    }

    if (oos != null) {
      try {
        postProcessEvent(event);
        Serializable serEvent = getPST().transform(event);
        oos.writeObject(serEvent);
        oos.flush();
        if (++counter >= CoreConstants.OOS_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) {
        if (oos != null) {
          try {
            oos.close();
          } catch (IOException ignore) {
          }
        }

        oos = null;
        addWarn("Detected problem with connection: " + e);
        if (reconnectionDelay > 0) {
          fireConnector();
        }
      }
    }
  }

  protected abstract void postProcessEvent(E event);
  protected abstract PreSerializationTransformer<E> getPST();

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

  protected static InetAddress getAddressByName(String host) {
    try {
      return InetAddress.getByName(host);
    } catch (Exception e) {
      // addError("Could not find address of [" + host + "].", e);
      return null;
    }
  }

  /**
   * The <b>RemoteHost</b> property takes the name of of the host where a corresponding server is running.
   */
  public void setRemoteHost(String host) {
    address = getAddressByName(host);
    remoteHost = host;
  }

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

  /**
   * The <b>Port</b> property 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> property.
   */
  public int getPort() {
    return port;
  }

  /**
   * The <b>reconnectionDelay</b> property 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> property.
   */
  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 previously open connection is dropped.
   *
   * @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);
          addInfo("Attempting connection to " + address.getHostName());
          socket = new Socket(address, port);
          synchronized (this) {
            oos = new ObjectOutputStream(socket.getOutputStream());
            connector = null;
            addInfo("Connection established. Exiting connector thread.");
            break;
          }
        } catch (InterruptedException e) {
          addInfo("Connector interrupted. Leaving loop.");
          return;
        } catch (java.net.ConnectException e) {
          addInfo("Remote host " + address.getHostName()
              + " refused connection.");
        } catch (IOException e) {
          addInfo("Could not connect to " + address.getHostName()
              + ". Exception is " + e);
        }
      }
      // addInfo("Exiting Connector.run() method.");
    }

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

}