Passenger: internal server error

Question

I installed Apache, Passenger and Sinatra and deployed an app. It gives error when trying to access:

An error occurred while starting up the preloader: it did not write a startup response in time.

Application root
    /var/www/html/test
Environment (value of RAILS_ENV, RACK_ENV, WSGI_ENV and PASSENGER_ENV)
    production
Ruby interpreter command

    /usr/local/bin/ruby

User and groups

    Unknown

Environment variables

    Unknown

Ulimits

    Unknown

How can I solve it?

---

Edit

In the application log, I found this line of error:

!> Ready
!> socket: unix:/tmp/passenger.1.0.14019/generation-0/backends/preloader.14049
!>

Gem list:

bigdecimal (1.2.0)
builder (3.2.0)
bundler (1.3.1)
daemon_controller (1.1.1)
fastthread (1.0.7)
io-console (0.4.2)
json (1.7.7)
minitest (4.3.2)
passenger (4.0.0.rc4)
psych (2.0.0)
rack (1.5.2)
rack-protection (1.4.0)
rake (0.9.6)
rdoc (4.0.0)
sequel (3.45.0)
sinatra (1.3.5)
test-unit (2.0.0.0)
tilt (1.3.4)

System version:

Ruby 2.0
Apache 2.2
Amazon EC2 Instance

The app was running fine with Ruby 1.9 and Passenger 3.0. I just upgraded to 2.0, and Passenger 3.0 does not even compile correctly. They suggested me to use Passenger Pre 4.0, and it compiled fine, but does not run the app...

Answer 1

I found the answer what is causing it in my case. In my config.ru I was redirecting STDOUT like this:

log = File.new("logs/std.log", "a+")
STDOUT.reopen(log)

Removing the redirect into the log and it starts up again.

Looks like passenger needs STDOUT to detect a working "preloader".

---

Edit: I'm currently using the following solution to redirect the log into a file and keep passenger happy (basically just duplicating stdout into the log file and not redirecting):

log = File.new("logs/std.log", "a+")
def STDOUT.write string
    log.write string
    super
end
STDOUT.sync = true

Answer 2

In case the above doesn't solve it for you, I had the exact same error message with a different cause.

In my case, we were using an external database server and that had gone down.

Bringing the external db server back up fixed the issue.

But before we solved this, we spent a bunch of time thinking about recompiling passenger, etc.

Hope this note saves someone some time.