How log an HTTP JSON request in Loopback app deployed on Heroku? - node.js

Question

An app (Loopback) is deployed on Heroku, and I need to to see the req body (the JSON) send to this app for debugging purpose.
So the access to the log is :
heroku logs --tail
The server.js is like the following :
var loopback = require('loopback');
var boot = require('loopback-boot');
var app = module.exports = loopback();
app.start = function() {
// start the web server
return app.listen(function() {
app.emit('started');
console.log('Web server listening at: %s', app.get('url'));
});
};
// Bootstrap the application, configure models, datasources and middleware.
// Sub-apps like REST API are mounted via boot scripts.
boot(app, __dirname, function(err) {
if (err) throw err;
// start the server if `$ node server.js`
if (require.main === module)
app.start();
});

Answer 1

As loopback extends express, we can use body parser module. So first install "body-parser"
Then add this code in serveur.js
var loopback = require('loopback');
var boot = require('loopback-boot');
var app = module.exports = loopback();
var bodyParser = require('body-parser');
// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }))
// parse application/json
app.use(bodyParser.json())
var logger = function(req, res, next) {
console.log(JSON.stringify(req.body, null, 2));
next(); // Passing the request to the next handler in the stack.
}
app.use(logger);
...
The remote log will display every request body received by the server.

Answer 2

If you don't want to modify your server.js file (and why would you), you can register a middleware logging all requests, refer to:
https://docs.strongloop.com/display/public/LB/Defining+middleware#Definingmiddleware-Overview
for more detail on how to register and write a middleware. routes:before would be a good phase to log requests.