title: "Request timeout" on Heroku
body: <p>I am having a problem deploying my web app on Heroku. I already set the database on MongoDB Atlas. The database is working when I am running "node app.js" locally. After deploying my project on Heroku I got an Application error and when I run "heroku logs --tail" I got the error below ; </p>
  
  <pre><code>2020-03-07T19:53:58.266177+00:00 heroku[web.1]: Idling
  2020-03-07T19:53:58.269259+00:00 heroku[web.1]: State changed from up to down
  2020-03-07T19:53:59.799552+00:00 heroku[web.1]: Stopping all processes with SIGTERM
  2020-03-07T19:53:59.987938+00:00 heroku[web.1]: Process exited with status 143
  2020-03-07T20:02:06.452667+00:00 heroku[web.1]: Unidling
  2020-03-07T20:02:06.468513+00:00 heroku[web.1]: State changed from down to starting
  2020-03-07T20:02:09.189010+00:00 heroku[web.1]: Starting process with command `node app.js`
  2020-03-07T20:02:11.522634+00:00 app[web.1]: Server started on port 3000
  2020-03-07T20:02:12.987457+00:00 heroku[web.1]: State changed from starting to up
  2020-03-07T20:02:41.597213+00:00 app[web.1]: (node:4) UnhandledPromiseRejectionWarning: MongooseServerSelectionError: connection &lt;monitor&gt; to 35.172.242.193:27017 closed
  2020-03-07T20:02:41.597235+00:00 app[web.1]: at new MongooseServerSelectionError (/app/node_modules/mongoose/lib/error/serverSelection.js:22:11)
  2020-03-07T20:02:41.597236+00:00 app[web.1]: at NativeConnection.Connection.openUri (/app/node_modules/mongoose/lib/connection.js:808:32)
  2020-03-07T20:02:41.597237+00:00 app[web.1]: at Mongoose.connect (/app/node_modules/mongoose/lib/index.js:333:15)
  2020-03-07T20:02:41.597237+00:00 app[web.1]: at Object.&lt;anonymous&gt; (/app/app.js:14:10)
  2020-03-07T20:02:41.597238+00:00 app[web.1]: at Module._compile (internal/modules/cjs/loader.js:955:30)
  2020-03-07T20:02:41.597238+00:00 app[web.1]: at Object.Module._extensions..js (internal/modules/cjs/loader.js:991:10)
  2020-03-07T20:02:41.597239+00:00 app[web.1]: at Module.load (internal/modules/cjs/loader.js:811:32)
  2020-03-07T20:02:41.597239+00:00 app[web.1]: at Function.Module._load (internal/modules/cjs/loader.js:723:14)
  2020-03-07T20:02:41.597239+00:00 app[web.1]: at Function.Module.runMain (internal/modules/cjs/loader.js:1043:10)
  2020-03-07T20:02:41.597240+00:00 app[web.1]: at internal/main/run_main_module.js:17:11
  2020-03-07T20:02:41.597341+00:00 app[web.1]: (node:4) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
  2020-03-07T20:02:41.597434+00:00 app[web.1]: (node:4) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
  2020-03-07T20:02:43.524590+00:00 heroku[router]: at=error code=H12 desc="Request timeout" method=GET path="/" host=protected-coast-44428.herokuapp.com request_id=9a7b66e6-1280-4d0c-b13d-10548513bc70 fwd="159.146.14.191" dyno=web.1 connect=0ms service=30000ms status=503 bytes=0 protocol=https
  2020-03-07T20:03:17.579588+00:00 heroku[router]: at=error code=H12 desc="Request timeout" method=GET path="/favicon.ico" host=protected-coast-44428.herokuapp.com request_id=3d335054-de74-4abb-982c-135988919edb fwd="159.146.14.191" dyno=web.1 connect=1ms service=30000ms status=503 bytes=0 protocol=https
  </code></pre>
  
  <p>Please note that I don't have any favicon.ico in my project. I had it in my previous project and I deleted that project on Heroku because of this error, and I don't know why I am still getting favicon on my error.</p>
  
  <p><strong>I made sure that I wrote the right user name and password in app.js and I added my IP in the whitelist as well.</strong></p>
  
  <pre><code>mongoose.connect("mongodb+srv://username:password*@cluster0-h6uqp.mongodb.net/todolistDB",
  { useNewUrlParser: true, useUnifiedTopology: true });
  </code></pre>