Deploying Node.JS express API App to Azure App Service - node.js

Question

I'm trying to deploy my Node.JS app to Azure App Service. I followed this introduction: https://learn.microsoft.com/de-de/azure/app-service/app-service-web-get-started-nodejs.
Here is the code of my app:
var express = require('express'); // Web Framework
var app = express();
var sql = require('mssql'); // MS Sql Server client
const { request } = require('http');
// Connection string parameters.
var sqlConfig = {
user: 'username',
password: 'password',
server: 'serveraddress',
database: 'databasename'
}
// Start server and listen on http://localhost:80/
var server = app.listen(80, function () {
var host = server.address().address
var port = server.address().port
console.log("app listening at http://%s:%s", host, port)
});
app.get('/tags', function (req, res) {
sql.connect(sqlConfig, function() {
var request = new sql.Request();
request.query('select * from dbo.Tag', function(err, recordset) {
if(err) console.log(err);
res.end(JSON.stringify(recordset)); // Result in JSON format
});
});
})
The app runs locally without any problems. Simple testing in browser by typing localhost:80/tags returns all tags as json.
But after deployment to Azure this error occurs:
2020-06-25T17:11:58.055Z ERROR - Container wearxapplication_0_ed215082 for site wearapplication did not start within expected time limit. Elapsed time = 230.0801107 sec
2020-06-25T17:11:58.074Z ERROR - Container wearxapplication_0_ed215082 didn't respond to HTTP pings on port: 8080, failing site start. See container logs for debugging.
2020-06-25T17:11:58.088Z INFO - Stopping site wearxapplication because it failed during startup.
What its mean? How solve it?

Answer 1

Looking at the errors, I believe you are using App Service on Linux with Single container configuration. If so, do not explicitly listen on port 80 or any other (unless you are deploying via custom container where you would have control of the docker file). Behind the scene, app service on Linux deploys a container and expose an auto-detected port (docker expose). Your explicit listening port is unlikely to match that auto-detected port. Replace you server bootstrap code with below snippet to let the port get picked up from environment:
// Start server and listen on http://localhost:port/ for local
const port = process.env.PORT || 1337; // for local debugging choose any available port
var server = app.listen(port, function () {
var host = server.address().address;
console.log("app listening at http://%s:%s", host, port);
});
One more thing to check is whether any of the dependencies (express, mssql in your case) failed to resolve at startup. This can happen when you have the dependency missing in node_modules folder. You can check that by starting Log Stream (you can find in Azure portal app service blade). You might see error like this
Log stream