Prax

A pure ruby alternative to Pow!!

Aka a Rack application spawner and proxy for simpler local development. Calling myapp.dev and subdomain.myapp.dev with no configuration is simpler than editing your hosts file, starting your applications manually on port 3000, etc.

My GNU/Linux fork of [Pow](pow.cx/) just broke on me badly, and I couldn’t read, less write the coffeescript it’s written in. I thus decided to try writing an alternative in Ruby. Good for me, because I now have a viable alternative, and learned a lot about TCP and UNIX sockets, the HTTP protocol, Rack and Ruby Threads.

Also, Prax only requires Ruby and the Rack gem, both you should have already installed if you are a Ruby Web developer.

Prax has been developed with MRI Ruby 1.9.3, but should be compatible with most ruby engines. It has been tested on:

- Ruby 1.8.7
- Ruby 1.9.3
- Rubinius 2.0.0 (HEAD)
- JRuby 1.7.0 (1.9 mode)

Please note that Ruby 1.8.7 and Rubinius in 1.8 mode also require the ‘sfl` (spawn for legacy) gem, because Ruby 1.8 doesn’t support ‘Process.spawn` which was introduced in Ruby 1.9.

Jruby in 1.8 mode isn’t supported, because ‘sfl` requires `fork` which isn’t available on all platforms (not even GNU/Linux). Also, Jruby 1.6.8 just doesn’t work with Prax, neither in 1.8 nor 1.9 modes.

First clone the repository, install the port forwarding script and NSSwitch extension.

$ git clone git://github.com/ysbaddaden/prax.git

$ cd prax/
$ ./bin/prax install

And you’re done! You only need to link your apps by going to your rails root path and calling link:

$ cd ~/Work/myapp
$ ./bin/prax link

Or install manually:

$ sudo cp install/initd /etc/init.d/prax
$ sudo chmod +x /etc/init.d/prax
$ sudo update-rc.d prax defaults
$ sudo /etc/init.d/prax start

$ cd prax/ext/
$ make
$ sudo make install

Edit /etc/nsswitch.conf and add prax to the hosts line, then restart your browser, otherwise it won’t use the newly configured prax resolver.

Create the ~/.prax directory and link your apps to it. You may link the same folder multiple times as different names to serve it from different domains.

$ mkdir ~/.prax
$ ln -sf ~/Work/myapp ~/.prax/

Eventually bin/prax start to run Prax, point your browser to http://myapp.dev/ and wait for your Rack app to spawn.

If you experience some regular slowness, where Prax seems to hang for periods of 5 seconds, this is because of the DNS resolution: NSSwitch tries a real DNS resolution before checking the prax extension. This usually creates an overhead of less than half a second, but sometimes takes 5 seconds on my Ubuntu 12.04.

You may try to move the ‘prax` NSSwitch extension before the `dns` one, so it looks like this:

hosts: files mdns4_minimal [NOTFOUND=return] prax dns mdns4

This will dramatically speed up the DNS resolution of *.dev domains, and it should never hang anymore. BUT please be aware that it may cause problems in regular DNS resolutions!

Mac OS X isn’t supported yet. Feel free to contribute!

This is a work in progress, and Prax is missing some features to be on par with Pow. Mostly on the configuration side of your development machine. Yet it’s already capable to start the HTTP server, spawn your apps, proxy requests, and more.

• HTTP Server

• HTTP Proxy

• Rack Handler (Racker)

• Rack Application spawn / restart / always restart

• SSL support (if certs and keys are generated)

• xip.io support

• GNU/Linux:

  • NSSwitch DNS resolver (resolves *.dev domains to 127.0.0.1)

  • firewall rule (redirects root ports 80/443 to user ports 20559/20558)

  • install script

• commands for the prax script:

  • prax always_restart

• Mac OS X:

  • firewall rule

  • DNS resolver

  • install script

• Julien Portalier <julien@portalier.com>

• Sam Stephenson, Nick Quaranto, 37signals for the sub comamnd

• pyromaniac for the initial NSSwitch extension