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What this is

This file is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

 * Copyright (C) The Apache Software Foundation. All rights reserved.
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.  */

package org.apache.log4j.varia;

import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.RollingFileAppender;
import org.apache.log4j.helpers.LogLog;

   This appender listens on a socket on the port specified by the
   Port property for a "RollOver" message. When such a message
   is received, the underlying log file is rolled over and an
   acknowledgment message is sent back to the process initiating the
   roll over.


This method of triggering roll over has the advantage of being operating system independent, fast and reliable.

A simple application {@link Roller} is provided to initiate the roll over.

Note that the initiator is not authenticated. Anyone can trigger a rollover. In production environments, it is recommended that you add some form of protection to prevent undesired rollovers. @author Ceki Gülcü @since version 0.9.0 */ public class ExternallyRolledFileAppender extends RollingFileAppender { /** The string constant sent to initiate a roll over. Current value of this string constant is RollOver. */ static final public String ROLL_OVER = "RollOver"; /** The string constant sent to acknowledge a roll over. Current value of this string constant is OK. */ static final public String OK = "OK"; int port = 0; HUP hup; /** The default constructor does nothing but calls its super-class constructor. */ public ExternallyRolledFileAppender() { } /** The Port [roperty is used for setting the port for listening to external roll over messages. */ public void setPort(int port) { this.port = port; } /** Returns value of the Port option. */ public int getPort() { return port; } /** Start listening on the port specified by a preceding call to {@link #setPort}. */ public void activateOptions() { super.activateOptions(); if(port != 0) { if(hup != null) { hup.interrupt(); } hup = new HUP(this, port); hup.setDaemon(true); hup.start(); } } } class HUP extends Thread { int port; ExternallyRolledFileAppender er; HUP(ExternallyRolledFileAppender er, int port) { = er; this.port = port; } public void run() { while(!isInterrupted()) { try { ServerSocket serverSocket = new ServerSocket(port); while(true) { Socket socket = serverSocket.accept(); LogLog.debug("Connected to client at " + socket.getInetAddress()); new Thread(new HUPNode(socket, er)).start(); } } catch(Exception e) { e.printStackTrace(); } } } } class HUPNode implements Runnable { Socket socket; DataInputStream dis; DataOutputStream dos; ExternallyRolledFileAppender er; public HUPNode(Socket socket, ExternallyRolledFileAppender er) { this.socket = socket; = er; try { dis = new DataInputStream(socket.getInputStream()); dos = new DataOutputStream(socket.getOutputStream()); } catch(Exception e) { e.printStackTrace(); } } public void run() { try { String line = dis.readUTF(); LogLog.debug("Got external roll over signal."); if(ExternallyRolledFileAppender.ROLL_OVER.equals(line)) { synchronized(er) { er.rollOver(); } dos.writeUTF(ExternallyRolledFileAppender.OK); } else { dos.writeUTF("Expecting [RollOver] string."); } dos.close(); } catch(Exception e) { LogLog.error("Unexpected exception. Exiting HUPNode.", e); } } }

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