Phusion Passenger integration question

[juanitogan]

What is the best practice for integrating chruby with Phusion Passenger? Is there one?

I have chruby auto switching enabled at the system level and it would be nice to not have to hard code the passenger line in ssl.conf (and/or httpd.conf) in addition to maintaining .ruby-version. For example, from my ssl.conf:

    PassengerRuby /opt/rubies/ruby-1.9.3-p484/bin/ruby

Something like the following would be more ideal if it were possible:

    PassengerRuby $RUBY_ROOT/bin/ruby

[postmodern]

auto-switching breaks down for things that do not use the shell (cron, apache, etc). I recommend simply installing your desired ruby via the package manager or into /usr/local via ruby-install. The beauty of /usr/local is it's already in $PATH, so no additional configuration needed.

[juanitogan]

Thanks. Problem is we already have another ruby in the path in /usr/bin that I need to ignore so I'm stuck with the default of /opt/rubies. Personally, I don't know where the best place is to put the app server rubies. I noticed that, by default, root does not have /usr/local in its path on our setup, and, of course, not /opt either.

[postmodern]

@juanitogan /usr/local/bin typically should precede /usr/bin in $PATH. You can also specify the absolute path to /opt/rubies/. Also, you probably should avoid running apps under root ;)

[juanitogan]

@postmodern Thank you, I agree on all those points. I can't say I know a lot about Linux but I have figured that much out. I believe the main app owner runs the app (according to settings I see in ssl.conf). I'm just not sure about who boots up the machine and starts httpd and all that (I believe I saw in some docs that Passenger runs as nobody). I've been using sudo bash to setup chruby and everything else but don't have any more control than that to change the low-level stuff.

I presume I could try setting a default ruby for the app user to simplify the PassengerRuby line, but then if I needed to run more than one ruby version as this app grows or splits into multiple apps, I would be back to hard coding the PassengerRuby line(s). I'm trying to establish the best practice for all future Ruby development here so I need to stick with what will work in most scenarios. [Yes, a bit odd that this fell to me who has little Linux and Ruby experience but, well, probably best if I don't explain that further.]

I suspect the only way to do what I was hoping for is for Passenger to add support for .ruby-version themselves. Such as:

PassengerRubyVersion /webapps/appone/.ruby-version

Anyhow, I just had to ask these questions just to be sure I wasn't missing something. Thank you for your help. And thank you, especially, for chruby and ruby-install -- they are much nicer than RVM to use (after I finally solved that annoying OpenSSL thing).

[juanitogan]

While investigating how Passenger sets the user I discovered the answer to my question. Set PassengerDefaultRuby to the default value of "ruby" (or don't set it at all):

PassengerDefaultRuby ruby

This tells Passenger to find Ruby through the path. Therefore, because Passenger starts the app as the user who owns config.ru and starts up in the same folder as .ruby-version, chruby executes and sets the path to the correct Ruby version.

Note: do not set PassengerRuby at all in this case unless you need to override the autoswitching that .ruby-version does.

[postmodern]

@juanitogan fascinating! Did you confirm passenger actually started rackup in a shell with chruby loaded? If this is the case, create a Wiki page for Passenger ASAP and I'll link it in the README.

[postmodern]

Double checking the [Passenger Documentation](http://www.modrails.com/documentation/Users guide Apache.html), you should also enable PassengerLoadShellEnvvars to ensure the application is loaded via bash -l -c ..., otherwise it uses this PassengerHelperAgent which I can't seem to find documentation on.

[sandstrom]

I dug in this recently, thought I'd add a note here. Also, chruby is awesome! Thanks @postmodern!

For Passenger Nginx the following is stated (Passenger 4.0 and later):

The passenger_ruby directive in the http block is also used as the default Ruby interpreter for Ruby web apps. You don’t have to specify a passenger_ruby in the http block though, because the default is to use the first ruby command found in $PATH.

However, I have not found this to be the case. It seems to use the OS-level ruby, unless I manually run chruby ruby-2.1.2 before, e.g. in /etc/profile.d/chruby.sh.

If anyone has got this working with nginx/passenger without setting the ruby version globally I'm super-happy to hear about it!

[FooBarWidget]

otherwise it uses this PassengerHelperAgent which I can't seem to find documentation on.

PassengerHelperAgent is the Passenger's core process, where most stuff happens. See https://github.com/phusion/passenger/wiki/Debugging-application-startup-problems#the-spawning-process-explained for a description of the spawning pipeline.

However, I have not found this to be the case.

That's because the PATH in Nginx can be different from the one in your shell. Read up on how environment variables work.

[postmodern]

If chruby is configured in ~/.bash_profile, you should enable passenger_load_shell_envvars so that bash -l -c is used to start the app.

[sandstrom]

I've configured it in /etc/profile.d/chruby.sh, and passenger_load_shell_envvars is enabled (it's on by default).

The content of my chruby.sh is:

source /usr/local/share/chruby/chruby.sh
source /usr/local/share/chruby/auto.sh

It seems like the working directory is set to the 'web root':
https://github.com/phusion/passenger/blob/ec926a662ed5e8c501dfca65aa0c97c9e0a5d588/ext/common/ApplicationPool2/SmartSpawner.h#L232

With rack apps the web root (in nginx) is often set to the ./public sub-directory, but I think the auto script traverses upwards until it hits a .ruby-version file, so I'm thinking it should work.

Perhaps there is something I've overlooked or misunderstood?

[postmodern]

@sandstrom one issue could be whether passenger cds into the directory before spawning the sub-shell, or within the sub-shell. chruby_auto only executes after the command, so bash -l -c 'rackup' would not automatically switch until after the first command.

[postmodern]

If that is the problem, I suspect explicitly calling chruby_auto after loading it would fix this.

[lcmen]

I also have question about integrating chruby with Phusion Passenger. Right now if I don't include auto switch script on system level (/etc/profile.d/chruby.sh) then my app won't start - it can not find bundler, even though it has PassengerRuby specified in Apache virtual host.

This is the error I got:

Error ID: 3150c494
  Error details saved to: /tmp/passenger-error-QHRe7r.html
  Message from application: cannot load such file -- bundler/setup (LoadError)
  /home/deployer/.rubies/ruby-2.1.3/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
  /home/deployer/.rubies/ruby-2.1.3/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
  /usr/lib/ruby/vendor_ruby/phusion_passenger/loader_shared_helpers.rb:263:in `block in run_load_path_setup_code'
  /usr/lib/ruby/vendor_ruby/phusion_passenger/loader_shared_helpers.rb:366:in `running_bundler'
  /usr/lib/ruby/vendor_ruby/phusion_passenger/loader_shared_helpers.rb:261:in `run_load_path_setup_code'
  /usr/share/passenger/helper-scripts/rack-preloader.rb:100:in `preload_app'
  /usr/share/passenger/helper-scripts/rack-preloader.rb:158:in `<module:App>'
  /usr/share/passenger/helper-scripts/rack-preloader.rb:29:in `<module:PhusionPassenger>'
  /usr/share/passenger/helper-scripts/rack-preloader.rb:28:in `<main>'