What is Pow?
Pow (a 37signals project) runs as your user on an unprivileged port, and includes both an HTTP and a DNS server. The installation process sets up a firewall rule to forward incoming requests on port 80 to Pow. It also sets up a system hook so that all DNS queries for a special top-level domain (.dev) resolve to your local machine.
Why use Pow?
- Easily host multiple Rack apps on your local machine under different domains e.g http://your-app.dev
- Configure local apps to run under SSL (explained below)
- Use the xip.io domain to visit your app from other devices on your local network
- Serve requests with multiple Pow workers
- Easy to configure, customise and works with multiple Rubies (via rbenv or RVM) and Bundler
Install Pow with this command;
curl get.pow.cx | sh
Next create a symlink in ~/.pow to your app’s base directory like so;
ln -s /full/path/to/your-app ~/.pow/your-app
Note: If you are running zsh with rbenv you may need to follow these instructions and add a PATH export to your ~/.powconfig file like so;
export PATH=`brew --prefix rbenv`/shims:`brew --prefix rbenv`/bin:$PATH
# then restart pow again with touch ~/.pow/restart.txt
This should be enough for you to see your app working at http://your-app.dev. The next steps assume you have this working.
Installing and configuring NGINX
Install NGINX via brew;
brew install nginx
By default brew will install and configure NGINX to listen on port 8080. We need to run it on port 443 (decrypting SSL and proxy-ing all requests through to our Pow server).
Using this config file we can set up NGINX with some good defaults, and tell it to look for sites in
mkdir -p /usr/local/etc/nginx/sites-enabled
mkdir -p /usr/local/etc/nginx/sites-available
curl -0 https://gist.github.com/matthutchinson/5815393/raw/9845b99433a0e1ebd2763b264643fe308ea74b4f/nginx.conf > /usr/local/etc/nginx/nginx.conf
Next we create our site configuration in
curl -0 https://gist.github.com/matthutchinson/5822750/raw/4790d7030d55a955b3c3a90fe2669b81235b95d2/your-app.dev > /usr/local/etc/nginx/sites-available/your-app.dev
Edit this file, setting the root (public) directory and replacing
your-app.dev throughout. Finally symlink it into sites-enabled;
ln -s /usr/local/etc/nginx/sites-available/your-app.dev /usr/local/etc/nginx/sites-enabled/your-app.dev
Generating an SSL Cert
You might have noticed that the config file you just edited referenced an SSL cert that we have not yet created.
In a tmp directory, let’s use this handy gist to generate it and move the cert files into place;
curl https://gist.github.com/matthutchinson/5815498/raw/9da28acd6bf0ce1666f39cc0351dd5eee764be8b/nginx_gen_cert.rb > /tmp/nginx_gen_cert.rb
ruby /tmp/nginx_gen_cert.rb your-app.dev
You should now have SSL cert files for your app properly configured and contained in
Trying it out
Thats it! To start NGINX (since we are listing on port 443) you need to run it with sudo;
Visit https://your-app.dev/ now to see your app served via HTTPS.
The web app can be restarted by running
touch tmp/restart.txt in the base directory. And you can control NGINX from the command line with flags like this;
sudo nginx -s start
sudo nginx -s stop
sudo nginx -s reload
Debugging with pry-remote
Since your app is now running in Pow’s own worker processes, to operate a live debugger you will need to use something like pry-remote.
First add the pry and pry-remote gems to your Gemfile (and
bundle install). Then to introduce a breakpoint use this in your code;
Fire off a request and when it stalls, run this command from your app’s base directory;
bundle exec pry-remote
A connection to the running worker process is established and you should be presented with a regular pry prompt. You can read more about pry-remote and pry here.
Your browser may complain about not trusting your new SSL cert - we can fix that!
Restart or open Safari to visit https://your-app.dev and click ‘Show Certificate’ from the warning dialog. Choose the ‘Trust’ drop-down and select ‘Always Trust’. This adds your newly generated cert to the OSX keychain.
Setting up more sites is easy, just add them with a similar NGINX site config, generate an SSL cert (using the helper script again) and symlink things into place.
You can play with Pow’s configuration (e.g timeouts, workers) by defining ENV variables in ~/.powconfig, for example;
Any change to ~/.powconfig needs a Pow restart;
I hope this guide has been useful. Comments or questions are always welcome.