Phusion Passenger internal server error

Question

I'm using Apache + Passenger on my Linode server, with a Postgresql-9.4 database. Every so often, I get the following error, but it is unpredictable and rights itself a few minutes later with no actions taken, so it is extremely hard to debug:

Internal server error
Phusion Passenger has listed more information about the error below.
An error occurred while starting the web application. It sent an unknown response type "".

Has anyone else run into an error like this, or know what it could imply?

Answer 1

Firstly go through this question, as it might solve your problem:

Passenger: internal server error

There are possible causes of problems listed here:

https://github.com/phusion/passenger/wiki/Debugging-application-startup-problems