log4js-node/lib/appenders/multiprocess.js

"use strict";
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;