azure node.js console.log not logging into stdout or stderr files - node.js

Question

I have a node.js app in azure (app service). The node.js is using the following modules
"scripts": {
"start": "node bin\/www",
"test": "mocha"
},
"dependencies": {
"async": "^1.5.2",
"bluebird": "^3.3.4",
"express": "^4.13.3",
"ioredis": "^1.15.1",
"lodash": "^4.6.1",
"socket.io": "^1.4.5"
},
"devDependencies": {
"chai": "^3.5.0",
"socket.io-client": "^1.4.5"
}
I wanted to enable the logging of app so i set the environment variable DEBUG = * using the portal->configure->app settings. since then, the app's express and socketio logs started to appear in /LogFiles/Application folder with cryptic name xxxxxx-nnnn-stderr-nnnnnnnnnnnnnn.txt
I added a console.log statement in one of the files in my app's lib folder
function MessageActions(redis, io) {
...
}
MessageActions.prototype.routeMessage = function(message) {
console.log('routeMessage: ' + JSON.stringify(message)); //this is not appearing anywhere in logs
var self = this;
return Promise.join(
self.checkUserMessage(message),
self.checkGroupMessage(message),
function(sendtarget, sendgroup) {
if(!sendtarget && !sendgroup) {
var pmsg = util.inspect(message);
throw new Error('Failed to route message: ' + pmsg);
}
}
);
}
I am sure that this function is being called as i could see the below error in the stderr file
[Error: Failed to route message: { ... }]
But i am not able to find the log statement added with console.log anywhere in this stderr file. also, there is no stdout file in the /LogFiles/Application folder.
How to add a log statement and where to check for it?
My IISNode.yml file has the following two lines
loggingEnabled: true
devErrorsEnabled: true

Answer 1

Please try to set the Application Logging (Filesystem) to on to enable the streaming log feature.
After that, you will find several logs files in /LogFiles/Application folder with cryptic name xxxxxx-nnnn-stdout-nnnnnnnnnnnnnn.txt which contain the output of your console.log().
But please notice the description:
Enable application logging to collect diagnostic traces from your web app code. You'll need to turn this on to enable the streaming log feature. This setting turns itself off after 12 hours.
To keep a persistence logging files in Node.js applications, you can use some node.js logging libraries like winston.

Answer 2

There is a way to see the console output live if you take the following steps:
Open website blade in Azure portal
Click on the tools icon
Click on the "Visual Studio Online" tool
Toggle the tool to "On"
...wait while the extension is enabled
Click the "Go->" icon under the tool toggle.
Once Visual Studio Online "Monaco" window is up, you can "Run" your application which should show your website in another window, but your "Monaco" window will have the console output from your application.
Hope this helps find your problem.

Answer 3

In your Index.js/Messages , replace the following code:
if (useEmulator) {
var restify = require('restify');
var server = restify.createServer();
server.listen(3978, function() {
console.log('test bot endpoint at http://localhost:3978/api/messages');
});
server.post('/api/messages', connector.listen());
}
else {
module.exports = { default: connector.listen() }
}
with:
if (useEmulator) {
var restify = require('restify');
var server = restify.createServer();
server.listen(3978, function() {
console.log('test bot endpoint at http://localhost:3978/api/messages');
});
server.post('/api/messages', connector.listen());
}
else {
var listener = connector.listen();
var withLogging = function(context, req) {
console.log = context.log;
listener(context, req);
}
module.exports = { default: withLogging }
}
This will override the console.log function. Hope , this will help.