ExpressJS framework (nodejs) log only stack errors to file

Question

I want to log only errors that would crash the system to a error.log separate file.

I'm already logging http requests with Morgan to a file using this code:

// create a write stream (in append mode)
var accessLogStream = fs.createWriteStream(__dirname + '/logs/access.log', {flags: 'a'})
// setup the logger
app.use(logger('short', {stream: accessLogStream}));

But I want to log to a separate file (error.log) this kind of app errors:

//Error handling, avoiding crash
process.on('uncaughtException', function (err) {
  console.error(err);
  console.log("Node NOT Exiting...");
});

How can I log error.stack to that file?

Note: expressjs.com/guide/error-handling.html

Jonathan Lonowski
– Jonathan Lonowski

2014-11-17 04:26:04 +00:00
Commented Nov 17, 2014 at 4:26 — Jonathan Lonowski
– Jonathan Lonowski, Commented Nov 17, 2014 at 4:26

ATC · Accepted Answer · 2014-11-17 02:55:47Z

2

process.on('uncaughtException', function (err) {
  console.error(err);
  console.log("Node NOT Exiting...");
  accessLogStream.write(err.stack);
});

Just writing to the stream like that ought to work! I haven't tested this though, may cause some issues due to writing with async. I usually just push an object to the dadabase. Something like

 {
     err : myError,
     time : new Date()
 }

answered Nov 17, 2014 at 2:55

ATC

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mdv · Accepted Answer · 2014-11-17 05:22:32Z

0

Based on Audun answer:

//Create error log Stream
var errorLogStream = fs.createWriteStream(__dirname + '/logs/error.log', {flags: 'a'})

//Error handling, avoiding crash
process.on('uncaughtException', function (err) {

var date = new Date();
  console.error(err);
  errorLogStream.write(date+ '\n'+ err.stack+'\n\n');

});

Log Output:

Mon Nov 17 2014 02:21:05 GMT-0300 (ART)
TypeError: Cannot read property 'payment_credits' of null
    at Promise.<anonymous> (/home/routes/api/chainWebhook.js:65:26)
    at Promise.<anonymou>(/home//node_modules/mongoose/node_modules/mpromise/lib/promise.js:177:8)
    at Promise.emit (events.js:95:17)

answered Nov 17, 2014 at 5:22

mdv

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