Notes from the NH Ruby / Rails Group, 16 Nov 2009: RVM and EC2

[Ted Roche]

Brian Turnbull and Nick Plante each had excellent presentations for the 
New Hampshire Ruby Rails Group's first meeting on the third Monday of 
the month, our new "regular meeting day." (We won't be having a December 
meeting, however; have a happy Kwanzaa, Hanukkah, Christmas, Saturnalia, 
Winter Solstice or non-denominational generic shopping holiday of your 
choice.)

Brian was up first, and talked about rvm, the Ruby Version Manager 
(slides here: http://www.slideshare.net/bturnbull/rvm-nhruby-nov-2009). 
RVM doesn't just allow you to have multiple versions of ruby on your 
machine; you've always been able to do that with side-by-side installs 
or linking or aliases or other kludges. RVM can be found at 
http://rvm.beginrescueend.com and can be installed as a Gem, from the 
Git repository or as a tarball. It's not Ruby code, actually, but shell 
scripts, and it allows not just switching of the current active version 
of ruby, but much more interestingly, the entire set of gems associated 
with a version! Multiple gemsets can be assigned an alias that lets you 
group your gems by function or project or client. RVM also provides a 
facility to dump the list of gems from one version or gemset and load it 
into another, allowing you to test out the migration of an existing 
system to a new version with much less hassle. Finally, rvm also lets 
you invoke multiple versions serially, passing them a command like "rvm 
1.86, 1.8.7, 1.9.1 rake spec" where rvm will run all your tests on 
multiple versions and report results, even in JSON if specified. This 
could be the core of a really simple Continuous Integration (CI) server 
in a single line of code!

Brian cautioned that rvm is early in its development cycle (current as 
of last night was 0.0.79) and changes are coming fast and furious, but 
it's worth taking some time to keep track of this very interesting 
development!

Brian also mentioned that rvm has some extensions to work with Bundler. 
Nick mentioned that Bundler, a project from Yehuda Katz (core 
contributor to both Ruby and jQuery) , is slated to become the default 
means of managing gems in Rails 3.0. Here's a good link to learn more: 
http://yehudakatz.com/2009/11/03/using-the-new-gem-bundler-today/

Nick Plante was up next, with his presentation on EC2 for Rails 
Development (http://zapnap.github.com/presentations/ec2-rubber/#0). Nick 
talked about the evolution of deployment of Rails (or Rack) solutions, 
moving from very painful to much easier with the introduction of 
Capistrano (http://capify.org/). He reviewed how simple it was to deploy 
an application with Capistrano, and then talked about the power of the 
Amazon Web Services (AWS) http://aws.amazon.com/ and Cloud Computing in 
general. Capistrano is focused on general deployment to a server, but 
the new add-on, Rubber (http://github.com/wr0ngway/rubber),  extends 
that to work with elastic computing resources like AWS' Elastic Compute 
Cloud (EC2). We walked through the basics of the 
install-configure-deploy scenario and then "Insert Demo Here." - he did 
it. Defying the Demo Gods (who had already tortured Brian a bit), Nick 
grabbed a copy of RedMine (http://www.redmine.org/) from GitHub, did the 
couple of minor configuration items needed to make it work locally 
(creating the session key, copying the sample database config to the 
live one, setting it to use SQLite3 locally and running db:migrate) and 
then set it up for deployment: first invoking Capistrano (doing some 
configuring) and then Vulcanizing (how else would you make rubber) the 
installation, then deploying it to a brand-new AWS instance. The steps 
flew by lightening-fast: the Amazon instance was up and running a minute 
after being invoked, then took a couple of minutes to install and 
configure Apache, Passenger, MySQL, the Redmine application, and sftp 
the development directory files to the instance. Within a few minutes, 
Nick could browse the machine and see the running application as well as 
ssh into the box and make any changes. There are innumerable options, of 
course, but they are all accessible by reviewing the configuration files 
and the source to tune it to your particular needs.

While we waited for the installation to complete, I brought up some of 
the customer's concerns and practitioner's insights from last Thursday's 
MonadLUG meeting on Cloud Computing and we talked about how those 
applied. I expressed concerns about how persistent data storage worked, 
since the cloud images were considered ephemeral. Nick pointed out that 
the instance, while running could have a local database and it could be 
in a master-slave replication arrangement with either another instance 
(within the AWS, there aren't bandwidth charges) or a hosted or local 
machine. Also mentioned was the Amazon Relation Database Service (RDS), 
which can provide a MySQL database instance with backups. So, there are 
lots of options.

Thanks to Brian and Nick for excellent presentations as well as 
organizing the meeting and bringing the pizza, to Tim and the folks at 
RMC Research for providing the excellent facilities and to all eleven 
who attended and participated in the meeting.

Remember, no Ruby meeting meeting in December. Stay tuned for a January 
announcement.


-- 
Ted Roche
Ted Roche&  Associates, LLC
http://www.tedroche.com