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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