Clustered appender for log4js.

[mkielar]

Hi,

I've created a multiprocess appender that uses process.send / worker.on(message, callback) mechanisms instead of sockets in order to synchronize logging.

It also allows use of multiple actual loggers in the master logger, and does not require user/programmer do point explicitely which mode to use.

See an example below:

if (cluster.isMaster) {

    // Init master logger
    log4js.configure({
        appenders: [
            { 
                // Adding only one, "clustered" appender. 
                // Note, there is no "mode" setting - the mode (master / worker) is automatucally determined from cluster.isMaster / cluster.isWorker
                type: "clustered",

                // Add as many "normal" appenders as you like. They wil all be used once the "clustered" master appender receives a loggingEvent
                appenders: [
                    { type: 'console' },
                    { type: 'file', filename: "log.log", maxLogSize: 10000000, backups: 10 },
                ]
            }
        ]
    });

    // Init logger like you used to
    var logger = log4js.getLogger("master");

    // Fork workers.
    for (var i = 0; i < 4; i++) {
        var worker = cluster.fork();
        logger.info("forked: " + i);
    }

} else {

    // Init worker loggers
    log4js.configure({
        appenders: [
            { 
                // Note, there again is no "mode" setting as the worker mode is automatically determined from cluster.isWorker
                type: "clustered",

                // Note, we do not add any other appenders here. Every message is sent to master logger.
            }
        ]
    });


    // Init logger like you used to
    var logger = log4js.getLogger("worker_" + cluster.worker.id);

    logger.info('message: ' + i + ' from worker ' + cluster.worker.id);

}

[nomiddlename]

Thanks for this, nice work. The multiprocess appender was written in the days before you could pass messages to workers (and indeed, before cluster became part of node core). This will be a good replacement for it, when you don't need to log to different hosts.

[SameerSiddiqui]

can you extend it to where i can have different loggers write to different files from Master comming from child.