title: heroku build succeed but url gives application error while heroku open
body: <pre><code>Counting objects: 3, done.
  Delta compression using up to 4 threads.
  Compressing objects: 100% (3/3), done.
  Writing objects: 100% (3/3), 327 bytes | 0 bytes/s, done.
  Total 3 (delta 2), reused 0 (delta 0)
  remote: Compressing source files... done.
  remote: Building source:
  remote:
  remote: -----&gt; Node.js app detected
  remote:
  remote: -----&gt; Creating runtime environment
  remote:
  remote:        NPM_CONFIG_LOGLEVEL=error
  remote:        NODE_VERBOSE=false
  remote:        NODE_ENV=production
  remote:        NODE_MODULES_CACHE=true
  remote:
  remote: -----&gt; Installing binaries
  remote:        engines.node (package.json):  8.11.1
  remote:        engines.npm (package.json):   5.6.0
  remote:
  remote:        Resolving node version 8.11.1...
  remote:        Downloading and installing node 8.11.1...
  remote:        npm 5.6.0 already installed with node
  remote:
  remote: -----&gt; Restoring cache
  remote:        Loading 2 from cacheDirectories (default):
  remote:        - node_modules
  remote:        - bower_components (not cached - skipping)
  remote:
  remote: -----&gt; Building dependencies
  remote:        Installing node modules (package.json + package-lock)
  remote:        up to date in 4.243s
  remote:
  remote: -----&gt; Caching build
  remote:        Clearing previous node cache
  remote:        Saving 2 cacheDirectories (default):
  remote:        - node_modules
  remote:        - bower_components (nothing to cache)
  remote:
  remote: -----&gt; Pruning devDependencies
  remote:        Skipping because npm 5.6.0 sometimes fails when running 'npm 
  prune' due to a known issue
  remote:        https://github.com/npm/npm/issues/19356
  remote:
  remote:        You can silence this warning by updating to at least npm 5.7.1 in your package.json
  remote:        https://devcenter.heroku.com/articles/nodejs-support#specifying-an-npm-version
  remote:
  remote: -----&gt; Build succeeded!
  remote: -----&gt; Discovering process types
  remote:        Procfile declares types -&gt; web
  remote:
  remote: -----&gt; Compressing...
  remote:        Done: 28.5M
  remote: -----&gt; Launching...
  remote:        Released v6
  remote:        https://ashishkr.herokuapp.com/ deployed to Heroku
  remote:
  remote: Verifying deploy... done.
  To https://git.heroku.com/ashishkr.git
  cfc5c8a..76b27d1  master -&gt; master
  </code></pre>
  
  <p>I have also a Procfile in my project root and have like:</p>
  
  <pre><code>web: node server.js
  </code></pre>
  
  <p>on doing heroku config i get the following result :
      MONGODB_URI: mongodb://:@ds163410.mlab.com:63410/ashishkr</p>
  
  <p>i hide the username and password for the security concern but i am sure that the username and password which i have entered is absolutely correct!</p>
  
  <p>in my package.json i have engines and start script also:</p>
  
  <pre><code> "scripts": {
    "test": "echo \"Error: no test specified\" &amp;&amp; exit 1",
    "start": "node server.js"
    },
   "engines": {
   "node": "8.11.1",
   "npm": "5.6.0"
    },
  </code></pre>
  
  <p>Anykind of help is appreciated !!</p>
  
  <p>Thanks !!</p>