title: NodeJS app build is successful (Heroku) but Application Error in heroku at the launch
body: <p>I am using Cloud 9 IDE.
  Build is successful when I do </p>
  
  <pre><code>git add .
  git commit -m "first_commit"
  git push heroku master
  </code></pre>
  
  <p>its result is this :</p>
  
  <pre><code>    Counting objects: 3, done.
  Delta compression using up to 8 threads.
  Compressing objects: 100% (2/2), done.
  Writing objects: 100% (3/3), 280 bytes | 0 bytes/s, done.
  Total 3 (delta 1), 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:        NPM_CONFIG_PRODUCTION=true
  remote:        NODE_VERBOSE=false
  remote:        NODE_ENV=production
  remote:        NODE_MODULES_CACHE=true
  remote: 
  remote: -----&gt; Installing binaries
  remote:        engines.node (package.json):  4.7.3
  remote:        engines.npm (package.json):   2.15.11
  remote:        
  remote:        Resolving node version 4.7.3...
  remote:        Downloading and installing node 4.7.3...
  remote:        npm 2.15.11 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)
  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; Build succeeded!
  remote: -----&gt; Discovering process types
  remote:        Procfile declares types     -&gt; (none)
  remote:        Default types for buildpack -&gt; web
  remote: 
  remote: -----&gt; Compressing...
  remote:        Done: 13.8M
  remote: -----&gt; Launching...
  remote:        Released v5
  remote:        https://still-reef-69131.herokuapp.com/ deployed to Heroku
  remote: 
  remote: Verifying deploy... done.
  To https://git.heroku.com/still-reef-69131.git
     c263d3a..ad74a53  master -&gt; master
  </code></pre>
  
  <p>This is my <strong>app.js</strong> : </p>
  
  <pre><code>var express = require("express") ;
  var app = express();
  
  app.use(express.static("public")) ;
  
  var sanitizer = require("express-sanitizer") ;
  
  var methodOverride = require("method-override") ;
  app.use(methodOverride("_method")) ;
  
  var bodyparser = require("body-parser") ;
  app.use(bodyparser.urlencoded({extended :true})) ;
  
  app.use(sanitizer()) ;
  var mongoose = require("mongoose") ;
  mongoose.connect("mongodb://localhost/restful_blog") ;
  
  var blogSchema = new mongoose.Schema({
      title: String,
      image: String,
      body: String,
      date: {type: Date, default: Date.now}
  });
  var blog = mongoose.model("blog", blogSchema);
  
  app.get("/", function(req,res){
      res.redirect("/blogs") ;
  }) ;
  
  app.get("/blogs" , function(req,res){
      blog.find({},function(err , maal){
          if(err) console.log(err) ;
          else res.render("index.ejs",{blogs : maal}) ;
      }) ;
  }) ;
  
  app.get("/blogs/new" , function(req,res){
      res.render("new.ejs") ;
  }) ;
  
  app.post("/blogs" , function(req,res){
      req.body.body = req.sanitize(req.body.body) ;
      blog.create({title : req.body.title , body : req.body.body , image : req.body.image} , function(err,newblog){
          if(err) console.log(err) ;
          else    res.redirect("/blogs") ;
      }) ;
  }) ;
  
  app.get("/blogs/:id" , function(req,res){
      blog.findById(req.params.id , function(err,maal){
          if(err) console.log(err) ;
          else {
              res.render("show.ejs" , {readmore : maal}) ;
          }
      }) ;
  }) ;
  
  app.get("/blogs/:id/edit" , function(req,res){
      blog.findById(req.params.id , function(err,maal){
          if(err) console.log(err) ;
          else {
              res.render("edit.ejs",{ blog:maal }) ;
          }
      }) ;
  }) ;
  
  app.put("/blogs/:id/edit" , function(req,res){
      req.body.body = req.sanitize(req.body.body) ;
      blog.findByIdAndUpdate(req.params.id , req.body , function(err,maal){
          if(err) console.log(err) ;
          else {
               res.redirect("/blogs/" + maal._id) ; }
      }) ;
  }) ;
  
  app.delete("/blogs/:id" , function(req,res){
      blog.findByIdAndRemove(req.params.id , function(err){    // No maal here as there is nothing 
          if(err) console.log(err) ;
          else res.redirect("/blogs") ;
      }) ;
  }) ;
  
  app.listen(process.env.PORT , process.env.IP , function(){
      console.log("Server is ON") ;
  }) ;  // Server start
  </code></pre>
  
  <p>And this is <strong>package.json</strong> : </p>
  
  <pre><code>{
    "name": "restful_blog_app",
    "version": "1.0.0",
    "description": "",
    "main": "app.js",
    "scripts": {
      "test": "echo \"Error: no test specified\" &amp;&amp; exit 1",
      "start": "node app.js"
    },
    "engines": {
      "node": "4.7.3" ,
      "npm": "2.15.11"
    },
    "author": "MeMyself&amp;I",
    "license": "ISC",
    "dependencies": {
      "body-parser": "^1.17.2",
      "ejs": "^2.5.6",
      "express": "^4.15.3",
      "express-sanitizer": "^1.0.2",
      "method-override": "^2.3.9",
      "mongoose": "^4.11.1"
    }
  }
  </code></pre>
  
  <p>But still there is an Application Error at the launch of the app : </p>
  
  <p><strong><em>Application error : <br>
  An error occurred in the application and your page could not be served. If you are the application owner, check your logs for details.</em></strong></p>
  
  <p><strong>Heroku Logs :</strong> </p>
  
  <pre><code>2017-10-26T11:41:48.495327+00:00 app[web.1]: 
  2017-10-26T11:41:48.495329+00:00 app[web.1]: events.js:141
  2017-10-26T11:41:48.495330+00:00 app[web.1]:       throw er; // Unhandled 'error' event
  2017-10-26T11:41:48.495330+00:00 app[web.1]:       ^
  2017-10-26T11:41:48.496369+00:00 app[web.1]: MongoError: failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
  2017-10-26T11:41:48.496373+00:00 app[web.1]:     at null.&lt;anonymous&gt; (/app/node_modules/mongoose/node_modules/mongodb/node_modules/mongodb-core/lib/connection/pool.js:280:12)
  2017-10-26T11:41:48.496371+00:00 app[web.1]:     at null.&lt;anonymous&gt; (/app/node_modules/mongoose/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:336:35)
  2017-10-26T11:41:48.496371+00:00 app[web.1]:     at emitOne (events.js:77:13)
  2017-10-26T11:41:48.496372+00:00 app[web.1]:     at emit (events.js:169:7)
  2017-10-26T11:41:48.496373+00:00 app[web.1]:     at emitTwo (events.js:87:13)
  2017-10-26T11:41:48.496373+00:00 app[web.1]:     at g (events.js:260:16)
  2017-10-26T11:41:48.496374+00:00 app[web.1]:     at emit (events.js:172:7)
  2017-10-26T11:41:48.496374+00:00 app[web.1]:     at Socket.&lt;anonymous&gt; (/app/node_modules/mongoose/node_modules/mongodb/node_modules/mongodb-core/lib/connection/connection.js:187:49)
  2017-10-26T11:41:48.496375+00:00 app[web.1]:     at Socket.g (events.js:260:16)
  2017-10-26T11:41:48.496375+00:00 app[web.1]:     at emitOne (events.js:77:13)
  2017-10-26T11:41:48.496376+00:00 app[web.1]:     at Socket.emit (events.js:169:7)
  2017-10-26T11:41:48.496376+00:00 app[web.1]:     at emitErrorNT (net.js:1269:8)
  2017-10-26T11:41:48.496377+00:00 app[web.1]:     at nextTickCallbackWith2Args (node.js:458:9)
  2017-10-26T11:41:48.496377+00:00 app[web.1]:     at process._tickCallback (node.js:372:17)
  2017-10-26T11:41:48.520747+00:00 app[web.1]: npm ERR! Linux 3.13.0-133-generic
  2017-10-26T11:41:48.522269+00:00 app[web.1]: npm ERR! npm  v2.15.11
  2017-10-26T11:41:48.510469+00:00 app[web.1]: 
  2017-10-26T11:41:48.521254+00:00 app[web.1]: npm ERR! argv "/app/.heroku/node/bin/node" "/app/.heroku/node/bin/npm" "start"
  2017-10-26T11:41:48.521574+00:00 app[web.1]: npm ERR! node v4.7.3
  2017-10-26T11:41:48.522544+00:00 app[web.1]: npm ERR! code ELIFECYCLE
  2017-10-26T11:41:48.522760+00:00 app[web.1]: npm ERR! restful_blog_app@1.0.0 start: `node app.js`
  2017-10-26T11:41:48.523180+00:00 app[web.1]: npm ERR! 
  2017-10-26T11:41:48.522963+00:00 app[web.1]: npm ERR! Exit status 1
  2017-10-26T11:41:48.523387+00:00 app[web.1]: npm ERR! Failed at the restful_blog_app@1.0.0 start script 'node app.js'.
  2017-10-26T11:41:48.523612+00:00 app[web.1]: npm ERR! This is most likely a problem with the restful_blog_app package,
  2017-10-26T11:41:48.523824+00:00 app[web.1]: npm ERR! not with npm itself.
  2017-10-26T11:41:48.524012+00:00 app[web.1]: npm ERR! Tell the author that this fails on your system:
  2017-10-26T11:41:48.524213+00:00 app[web.1]: npm ERR!     node app.js
  2017-10-26T11:41:48.524422+00:00 app[web.1]: npm ERR! You can get information on how to open an issue for this project with:
  2017-10-26T11:41:48.524630+00:00 app[web.1]: npm ERR!     npm bugs restful_blog_app
  2017-10-26T11:41:48.525228+00:00 app[web.1]: npm ERR!     npm owner ls restful_blog_app
  2017-10-26T11:41:48.524834+00:00 app[web.1]: npm ERR! Or if that isn't available, you can get their info via:
  2017-10-26T11:41:48.525418+00:00 app[web.1]: npm ERR! There is likely additional logging output above.
  2017-10-26T11:41:48.525037+00:00 app[web.1]: npm ERR! 
  2017-10-26T11:41:48.530341+00:00 app[web.1]: 
  2017-10-26T11:41:48.530616+00:00 app[web.1]: npm ERR! Please include the following file with any support request:
  2017-10-26T11:41:48.530813+00:00 app[web.1]: npm ERR!     /app/npm-debug.log
  2017-10-26T11:41:48.620147+00:00 heroku[web.1]: State changed from starting to crashed
  2017-10-26T11:41:48.607867+00:00 heroku[web.1]: Process exited with status 1
  2017-10-26T11:42:04.141504+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=still-reef-69131.herokuapp.com request_id=525c4f82-20fc-4d02-9b21-848c0011e451 fwd="115.97.201.36" dyno= connect= service= status=503 bytes= protocol=https
  2017-10-26T11:42:05.503594+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=still-reef-69131.herokuapp.com request_id=648fd443-3661-49d1-87f7-7ba27c065dff fwd="115.97.201.36" dyno= connect= service= status=503 bytes= protocol=https
  2017-10-26T11:43:56.405496+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=still-reef-69131.herokuapp.com request_id=6e94416f-ac28-4196-8ecd-7f701e96785e fwd="115.97.201.36" dyno= connect= service= status=503 bytes= protocol=https
  2017-10-26T11:43:57.089498+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=still-reef-69131.herokuapp.com request_id=b2069968-30b5-4875-9b04-ad3fa5c38419 fwd="115.97.201.36" dyno= connect= service= status=503 bytes= protocol=https
  </code></pre>
  
  <hr>
  
  <p>Any Ideas where am I going wrong ??</p>