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A fork of Apache Log4j v1 with security patches, and repackaged as `io.confluent:confluent-log4j`

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.log4j.net;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.InterruptedIOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Vector;

/**
  

The TelnetAppender is a log4j appender that specializes in writing to a read-only socket. The output is provided in a telnet-friendly way so that a log can be monitored over TCP/IP. Clients using telnet connect to the socket and receive log data. This is handy for remote monitoring, especially when monitoring a servlet.

Here is a list of the available configuration options:

Name Requirement Description Sample Value
Port optional This parameter determines the port to use for announcing log events. The default port is 23 (telnet). 5875
@author Jay Funnell */ public class TelnetAppender extends AppenderSkeleton { private SocketHandler sh; private int port = 23; /** This appender requires a layout to format the text to the attached client(s). */ public boolean requiresLayout() { return true; } /** all of the options have been set, create the socket handler and wait for connections. */ public void activateOptions() { try { sh = new SocketHandler(port); sh.start(); } catch(InterruptedIOException e) { Thread.currentThread().interrupt(); e.printStackTrace(); } catch(IOException e) { e.printStackTrace(); } catch(RuntimeException e) { e.printStackTrace(); } super.activateOptions(); } public int getPort() { return port; } public void setPort(int port) { this.port = port; } /** shuts down the appender. */ public void close() { if (sh != null) { sh.close(); try { sh.join(); } catch(InterruptedException ex) { Thread.currentThread().interrupt(); } } } /** Handles a log event. For this appender, that means writing the message to each connected client. */ protected void append(LoggingEvent event) { if(sh != null) { sh.send(layout.format(event)); if(layout.ignoresThrowable()) { String[] s = event.getThrowableStrRep(); if (s != null) { StringBuffer buf = new StringBuffer(); for(int i = 0; i < s.length; i++) { buf.append(s[i]); buf.append("\r\n"); } sh.send(buf.toString()); } } } } //---------------------------------------------------------- SocketHandler: /** The SocketHandler class is used to accept connections from clients. It is threaded so that clients can connect/disconnect asynchronously. */ protected class SocketHandler extends Thread { private Vector writers = new Vector(); private Vector connections = new Vector(); private ServerSocket serverSocket; private int MAX_CONNECTIONS = 20; public void finalize() { close(); } /** * make sure we close all network connections when this handler is destroyed. * @since 1.2.15 */ public void close() { synchronized(this) { for(Enumeration e = connections.elements();e.hasMoreElements();) { try { ((Socket)e.nextElement()).close(); } catch(InterruptedIOException ex) { Thread.currentThread().interrupt(); } catch(IOException ex) { } catch(RuntimeException ex) { } } } try { serverSocket.close(); } catch(InterruptedIOException ex) { Thread.currentThread().interrupt(); } catch(IOException ex) { } catch(RuntimeException ex) { } } /** sends a message to each of the clients in telnet-friendly output. */ public synchronized void send(final String message) { Iterator ce = connections.iterator(); for(Iterator e = writers.iterator();e.hasNext();) { ce.next(); PrintWriter writer = (PrintWriter)e.next(); writer.print(message); if(writer.checkError()) { ce.remove(); e.remove(); } } } /** Continually accepts client connections. Client connections are refused when MAX_CONNECTIONS is reached. */ public void run() { while(!serverSocket.isClosed()) { try { Socket newClient = serverSocket.accept(); PrintWriter pw = new PrintWriter(newClient.getOutputStream()); if(connections.size() < MAX_CONNECTIONS) { synchronized(this) { connections.addElement(newClient); writers.addElement(pw); pw.print("TelnetAppender v1.0 (" + connections.size() + " active connections)\r\n\r\n"); pw.flush(); } } else { pw.print("Too many connections.\r\n"); pw.flush(); newClient.close(); } } catch(Exception e) { if (e instanceof InterruptedIOException || e instanceof InterruptedException) { Thread.currentThread().interrupt(); } if (!serverSocket.isClosed()) { LogLog.error("Encountered error while in SocketHandler loop.", e); } break; } } try { serverSocket.close(); } catch(InterruptedIOException ex) { Thread.currentThread().interrupt(); } catch(IOException ex) { } } public SocketHandler(int port) throws IOException { serverSocket = new ServerSocket(port); setName("TelnetAppender-" + getName() + "-" + port); } } }




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