I would suggest you to not write directly but redirect output to a file.
node app.js > file.log
keep it simple.
On 4/28/14, 5:45 AM, gen chen wrote:
> I am now working on a node.js project based on cluster. I got stuck on
> the logging. After doing some research, I worked out a solution. here
> is it. i don't know if it is a good idea. The idea is like this. only
> master process can wirte to the log file, if the current process is a
> worker, then it send a log message to the master and then write to the
> log file while the master can directly write to the log file. this can
> avoid multiple process open and write to a same file.
>
> var util = require('util');
> var fs = require('fs');
> var cluster = require('cluster');
>
> var logger = module.exports;
>
> var levels = ['debug', 'info', 'warn', 'error', 'fatal'];
> var logLevel = 'debug';
>
> var logfile = null;
> var errorLogfile = null;
>
>
> if(cluster.isMaster){
>
> logfile = fs.createWriteStream('debug.log', {flags:'a'});
> errorLogfile = fs.createWriteStream('error.log', {flags:'a'});
>
> cluster.on('online', function(worker){
> //collect log message from child and write to logfile.
> worker.on('message', function(msg){
> if(msg.type == 'logging') {
> var level = msg.data.level;
> var logStr = msg.data.msg;
> if(levels.indexOf(level) >= levels.indexOf('error')){
> errorLogfile.write(logStr + '\n');
> }else{
> logfile.write(logStr + '\n');
> }
> }
> });
> });
> }
>
>
> function log(level, args){
>
> if(levels.indexOf(level) < levels.indexOf(logLevel)) return;
>
> var args = Array.prototype.slice.call(args);
>
> args = args.map(function(a){
> if(typeof a !== 'string')
> return JSON.stringify(a);
> else return a;
> });
> var msg = util.format.apply(null, args);
>
> var out = [];
> out.push(new Date());
> out.push('[' + level.toUpperCase() + ']');
> out.push(msg);
>
>
> if(cluster.isMaster){
>
> //write directly to the log file
> if(levels.indexOf(level) >= levels.indexOf('error')){
> errorLogfile.write(out.join(' ') + '\n');
> }else{
> logfile.write(out.join(' ') + '\n');
> }
>
> }else{
>
> //send to master
> cluster.worker.process.send({
> type : 'logging',
> data : {
> level : level,
> msg : out.join(' ')
> }
> });
> }
>
> }
>
>
> logger.debug = function(){log('debug', arguments);}
> logger.info = function(){log('info', arguments);}
> logger.warn = function(){log('warn', arguments);}
> logger.error = function(){log('error', arguments);}
> logger.fatal = function(){log('fatal', arguments);}
>
>
>
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