jhthorsen - Howto deploy #Mojolicious to @dotcloud

Saturday, September 15, 2012

After sending some tweets with dotcloud I’ve figured out how to deploy Mojolicious to dotcloud as a perl-worker.

The way I previously deployed was using the standard perl service, with a uWSGI frontend. The really cool thing about a perl-worker is that the mojo web application is running persistently allowing it to:

Handle more requests in parallel
Use WebSockets
Allow the mojo app to do other tasks periodically

NOTE: The above is only available if you do async programming. (yes, you can do both sync/async in mojolicious)

DISCLAIMER: When reading this howto, you should already know the basics about Mojolicious and dotcloud.

So here is how I did it:

dotcloud.yml

This file is the build file used by dotcloud to figure out which services to set up. Here is an example file that I use:

www:
  type: perl-worker
  config:
    perl_version: v5.16.x
  ports:
    www: http

The “magical” config setting here is “ports”. This allow the perl-worker to be accessible from the outside. Which port is given to you is then set in the environment.yml file created by dotcloud.

supervisord.conf

The next file to set up is supervisord.conf file which tells dotcloud which application to run. Here the file I use:

[program:cool_app]
command = /home/dotcloud/current/script/dotcloud.sh

This simply tells Supervisor to execute the “command” once pushed to dotcloud. The shell script then need to start your mojo app the right way. Here is the content of “dotcloud.sh”:

#!/bin/sh
export ENVIRONMENT_FILE="/home/dotcloud/environment.yml";
export MOJO_LOG_LEVEL="info";

# export environment.yml as shell variables
$( perl -p -e's/:\s+/=/;s/^/export /' $ENVIRONMENT_FILE );

if [ "x$DOTCLOUD_PROJECT" = "xcool_app_test" ]; then
    export MOJO_LOG_LEVEL="debug";
fi

exec /home/dotcloud/current/script/cool_app daemon --listen "http://*:$PORT_WWW";

The trick is to fetch the “PORT_WWW” variable from the environment.yml file and then start the “cool_app” with the correct listen port. The “if” in the middle is a trick I use to set the debug level once pushed to my test-instance. It is not required.

NOTE: Remember to make both “script/cool_app” and “script/dotcloud.sh” executable.

Pushing the app to dotcloud

After creating the files above, your directory tree should look something like this:

cool_app.conf      # app config file
dotcloud.yml
lib/               # your mojo app
Makefile.PL        # build file for your mojo app
public/            # mojo public files
script/cool_app    # executable
script/dotcloud.sh # executable
supervisord.conf
t/                 # perl unittests

NOTE: The directory structure will look different if you’re deploying a mojo lite app.

Run the commands below to create and push the app:

dotcloud create cool_app
dotcloud push cool_app

After this you should see something like this in the output from “dotcloud”:

Deployment finished. Your application is available at the following URLs
www: http://cool_app-username.dotcloud.com/

And then you’re done!

Other resources

The downside about this is that you can’t serve your static files directly with nginx. To remove this “burden” from your mojo app, you should consider setting up cloudflare in front of your application. It’s a kick ass service for both DNS and content delivery.