Openshift - 503 Service Temporarily Unavailable when i am accessing the app

I got an app hosted on Openshift here , using node.js and mongo db. It was running perfectly yesterday and today when i am accessing the same, i am getting

Service Temporarily Unavailable Error

I searched some threads and tried this command

rhc tail -a news

and result was

npm ERR! node -v v0.6.20 npm ERR! npm -v 1.1.37 npm ERR! code

ELIFECYCLE npm ERR! message OpenShift-Sample-App@1.0.0 start: `node

server.jsnpm ERR! messagesh "-c" "node server.js"` failed with 1

npm ERR! npm ERR! Additional logging details can be found in: npm ERR!

/var/lib/openshift/4eb0c449f78a4d7e937726185b5e636e/app-root/runtime/repo/npm-debug.log

npm ERR! not ok code undefined npm ERR! not ok code 1

I have also tried 

rhc app status -a news

and result was

RESULT: Geargroup nodejs-0.6+mongodb-2.2 is started

also i tried to restart my app

rhc app restart

and it restarted properly. Could you suggest me what is the issue.?

As mentioned by Hardy, i still dont know which resource got exceeded. But have fixed it now.

Here is what i did.

  1. just get remote access to your app console as described here.

  2. ssh into the console with a client like PuTTy or Cygwin.

  3. just check the status of your app by typing ctl_app status. for me it came like : App is currently inaccessible or stopped.

  4. just start it by typing ctl_all start

Now app is working as previously.

Are you using a free OpenShift account (free grear)? If so, what is your app doing? Is it very CPU or memory intensive. Your gears are monitored using cgroups and once you exceed any resource limit (cpu, memory, threads) your app gets killed. In this case you would get the message you describe. Unfortunately there is no way of telling which resource you exceeded and you don't get a notification that this was the problem. At least that is something I experienced with my apps. Of course there could be other problems with your app.