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) {
                    StringBuilder buf = new StringBuilder();
                    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);
        }

    }
}