org.apache.log4j.net.TelnetAppender Maven / Gradle / Ivy

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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
 * 
 * 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.
 */

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);
	}

    }
}