"unicorn -D" always returns 0 "success" (even when failed to load)

Iñaki Baz Castillo ibc at aliax.net
Tue Dec 22 21:20:59 EST 2009

Hi, I'm writing a Debian init script for unicorn and realized that when 
starting unicorn with daemonize option, the command always returns 0, even if 
the start action failed (due for example Errno::EADDRINUSE).

Returning 0 in such case is not good as it breaks service init scripts or 
service controllers (as HeartBeat) that fully rely on the appropriate exit 

Is there some way to determine if unicorn failed to start when using "-D"?

Another related issue: When the Rack config.ru file contains some error (as a 
typo) the worker(s) returns 1 (at the moment usually). Then unicorn master 
process reapes the terminated worker process and restarts it. Of course it 
would fail again and again. Anyhow "unicorn -D" returns 0 again (success).

Usually if a worker (all the workers) fail to start at the moment of running 
it, it obviously means that there is some error in the application with 
prevents it to run. It could be great if Unicorn could detect it.

For that I suggest something as a new option "--validation-time TIME". Let's 
suppose TIME is 5 seconds. In case *all* the workers fail within 5 seconds 
after starting unicorn, then unicorn understands that the Rack application is 
wrong (or any other error as Errno::EADDRINUSE) so terminates all the workers 
and itself (and hopefully returns 1 or any other non-zero exit status).

Of course, all the above means that Unicorn should wait TIME seconds before 
being daemonized (so after TIME seconds it can decide which code to return).

Does it make sense? Thanks a lot.

Iñaki Baz Castillo <ibc at aliax.net>

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