log4js-node/lib/appenders/multiprocess.js

var log4js = require('../log4js'),
    net = require('net'),
    END_MSG = '__LOG4JS__';

/**
 * Creates a server, listening on config.loggerPort, config.loggerHost.
 * Output goes to config.actualAppender (config.appender is used to
 * set up that appender).
 */
function logServer(config) {

    /**
     * Takes a utf-8 string, returns an object with
     * the correct log properties.
     */
    function deserializeLoggingEvent(clientSocket, msg) {
        var loggingEvent;
        try {
          loggingEvent = JSON.parse(msg);
          loggingEvent.startTime = new Date(loggingEvent.startTime);
	        loggingEvent.level = log4js.levels.toLevel(loggingEvent.level.levelStr);
        } catch (e) {
            // JSON.parse failed, just log the contents probably a naughty.
            loggingEvent = {
                startTime: new Date(),
                categoryName: 'log4js',
                level: log4js.levels.ERROR,
                data: [ 'Unable to parse log:', msg ]
            };
        }

        loggingEvent.remoteAddress = clientSocket.remoteAddress;
        loggingEvent.remotePort = clientSocket.remotePort;

        return loggingEvent;
    }

    var actualAppender = config.actualAppender,
        server = net.createServer(function serverCreated(clientSocket) {
            clientSocket.setEncoding('utf8');
            var logMessage = '';

            function logTheMessage(msg) {
                if (logMessage.length > 0) {
                    actualAppender(deserializeLoggingEvent(clientSocket, msg));
                }
            }

            function chunkReceived(chunk) {
                var event;
                logMessage += chunk || '';
                if (logMessage.indexOf(END_MSG) > -1) {
                    event = logMessage.substring(0, logMessage.indexOf(END_MSG));
                    logTheMessage(event);
                    logMessage = logMessage.substring(event.length + END_MSG.length) || '';
                    //check for more, maybe it was a big chunk
                    chunkReceived();
                }
            }

            clientSocket.on('data', chunkReceived);
            clientSocket.on('end', chunkReceived);
        });
        
    server.listen(config.loggerPort || 5000, config.loggerHost || 'localhost');

    return actualAppender;
}

function workerAppender(config) {
    var canWrite = false,
        buffer = [],
        socket;

    createSocket();

    function createSocket() {
        socket = net.createConnection(config.loggerPort || 5000, config.loggerHost || 'localhost');
        socket.on('connect', function() {
            emptyBuffer();
            canWrite = true;
        });
        socket.on('timeout', socket.end.bind(socket));
        //don't bother listening for 'error', 'close' gets called after that anyway
        socket.on('close', createSocket);
    }

    function emptyBuffer() {
        var evt;
        while ((evt = buffer.shift())) {
            write(evt);
        }
    }

    function write(loggingEvent) {
        socket.write(JSON.stringify(loggingEvent), 'utf8');
        socket.write(END_MSG, 'utf8');
    }

    return function log(loggingEvent) {
        if (canWrite) {
            write(loggingEvent);
        } else {
            buffer.push(loggingEvent);
        }
    };
}

function createAppender(config) {
    if (config.mode === 'master') {
        return logServer(config);
    } else {
        return workerAppender(config);
    }
}

function configure(config, options) {
    var actualAppender;
    if (config.appender && config.mode === 'master') {
        log4js.loadAppender(config.appender.type);
        actualAppender = log4js.appenderMakers[config.appender.type](config.appender, options);
        config.actualAppender = actualAppender;
    }
    return createAppender(config);
}

exports.appender = createAppender;
exports.configure = configure;