How to fix Incomplete response received from application from nginx / passenger in a rails application

I was trying to deploy a simple rails application( stack is Ruby 2.2.4, Rails 4.2.5, with passenger/Nginx as application/web server) to AWS EC2 and I was getting a weird error.

Incomplete response received from application

And looking at the Nginx/passenger logs I wasn't able to figure out the issue first hand. Then == I tried to debug in detail and changed the passenger_app_env to development == so that I can see the debug logs in details and voila.!! I figured out how stupid I was.

Checking the logs, I see:

app error: Missing `secret_token` and `secret_key_base` for 'production' environment

== Yep, you got it right, I forgot to set the secret_token in my env, and it caused the error. ==

After generating the secret_token using

RAILS_ENV=production rake secret

and exporting it to the bash env using:

export SECRET_KEY_BASE=secret_token

and restarting Nginx using

touch tmp/restart.txt

I was able to bring my rails app online.

As they say:

Making mistakes simply mean you are learning faster. ~Weston H. Agor

Hope I save someone's time in future. :)