Automagic application server configurator

Monit/Nginx/Unicorn application server configurator using deployment via git (simply git push applications to your server to deploy them).

This tool automatically generates server configs for Monit, Nginx and Unicorn to host your Rack-based (Rails) applications. Running it automatically in git update hooks provides an automatic deployment of applications whenever the repository is updated on the server.

Requirements

A server running Monit, Nginx and having Git and Ruby with RubyGems installed.

Install

gem install appserver

Or check out the repository on github.

Setup

Initialize an appserver directory

To run applications, you need to initialize an appserver directory first. To do so, run appserver init.

$ appserver init /var/webapps

An appserver directory holds configuration files and everything needed to run multiple applications (application code, temp files, log files, ...). You can customize settings by editing the appserver.conf.rb configuration file. All other files are updated automatically and should not be modified manually.

Activate generated Nginx configuration

Modify your system's Nginx configuration (e.g. /etc/nginx/nginx.conf on Ubuntu) to include the generated nginx.conf inside a http statement. Reload Nginx to apply the configuration changes.

/etc/nginx/nginx.conf:

⋮
http {
  ⋮
  include /var/webapps/nginx.conf;
}
⋮

Activate generated Monit configuration

Modify your system's Monit configuration (e.g. /etc/monit/monitrc on Ubuntu) to include the generated monitrc at the bottom. Reload Monit to apply the configuration changes.

/etc/monit/monitrc:

⋮
include /var/webapps/monitrc

Optional: Activate generated Logrotate configuration

Modify your system's Logrotate configuration (e.g. /etc/logrotate.conf on Ubuntu) to include the generated logrotate.conf at the bottom. Logrotate is typically executed from cron, so there's no daemon to reload to apply the configuration changes.

/etc/logrotate.conf:

⋮
include /var/webapps/logrotate.conf

Deploying an application

Deploying an application is easy: simply run appserver deploy /path/to/repository.git to deploy the application and run appserver update to update generated configuration files.

$ cd /var/webapps
$ appserver deploy /var/git/myblog.git
$ appserver update

After that, the application will be automatically deployed every time you push changes to the repository.

Using Ruby Gems

To use Ruby Gems in an application, either install the required gems globally (not recommended), or use Bundler. If a Gemfile is detected when deploying an application, a gem bundle with the required gems will be created automatically. Rails 3 supports Bundler out of the box, for older versions or other frameworks, you might need to add some initializing code (which basically means to call Bundle.setup). See the Bundler website for details.

How it works

In general: every appserver command (except init) needs to be run from an initialized appserver directory (or you need to specify the appserver directory using the -d option). Also, appserver commands do never modify anything outside their current appserver directory.

The deploy command does two things:

1. It checks out the repository (master branch by default) and installs it to the appserver directory (which also involves symlinking temp directories, creating a gem bundle, and so on).
2. It installs an update hook script to the repository, that runs the deploy command everytime you push to the repository from now on.

After deploy, there's a ready-to-run copy of the application in the appserver directory, that just needs to be started.

The update command updates generated configuration files for Monit and Nginx. If you properly included the generated configuration files to your system configuration, Monit will automatically detect updated configuration files and reload the corresponding system processes (even itself).

For every deployed application, Monit is configured to start a Unicorn server process with the configured number of instances (Unicorn workers) and keep it running. Whenever a different revision of the application is deployed, it gracefully restarts the server process (using Unicorn's SIGUSR2/SIGQUIT mechanism) without interrupting requests. Nginx is configured to forward incoming HTTP requests to the Unix socket of the Unicorn process for the corresponding Rack application. Static files are served directly by Nginx for performance.

Btw, Monit only runs periodically (typically 60 second cycles), so you might have to wait a few seconds until changes are recognized and processes are reloaded.

Security considerations

to be done...

Author

Andreas Neuhaus :: http://zargony.com/