Tag Archives: ruby

Customized Capistrano tasks per-host

This was something that took a while to piece together, and most of the links I found on the net pointed to vastly more difficult solutions.

The problem: I wanted to create iptables rules that would lock down the back-end private IP’s of my servers to allow access only from each other. Every time I add or remove a server, these rules need to be rewritten, so my Capistrano deployment seemed the logical place to do this (as opposed to my server installation scripts).

But…each server needed its own rules, which would be different from each other because the interfaces would be different. And in Capistrano, this isn’t really the default mode of operation. It’s easy to customize tasks by role, but doing it by host (while allowing for easy addition or removal of hosts) is harder.

You do have access to $CAPISTRANO:HOST$ within your tasks; however, this is only evaluated within the context of certain functions like “run”. Which may or may not help…in this case, it did not.

Here are the relevant snippets from what I did. First, I added a custom attribute ‘internal’ to each host, which is its internal IP address:

Then, inside my :update_rules task, I needed an array of all the internal IPs, so I find the servers for the task (using find_servers_for_task) and iterate over them to pull out the :internal attribute:

And finally, the part that does something different on each server…here, for each server, I add rules for all of the internal IPs; note the :hosts option on the run command, which specifies the task will run on only that host (sorry for the line wrapping).

I’m looping through all the servers, running a specific task on each of them. This isn’t perfect; it will run on only one host at a time, rather than running in parallel…but it gets the job done!

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Learning Ruby and Rails

A few weeks ago, I decided it was high time to get back to writing code. NewsGator’s code is based on Microsoft .net, and much of my career has been building products for Windows. Given that, I figured it was time to learn how the other half lives.

I started this adventure learning PHP (which reminded me a lot of pre-.net ASP, with some extra language constructs like classes sort of bolted on), and dabbling enough with MySQL that I could do what I wanted.

Then I decided it was time to learn Ruby and Rails. It actually took a fair amount of effort to figure out how to get started there, and I didn’t find any blog posts that really laid it out all in one place…so here is what I did.

First, I wanted to learn the language without the additional complexity of Rails on top of it. I downloaded the ruby_koans project, which essentially has a bunch of test cases, and code that you need to fix in order to continue. It was a unique way to learn, I thought, but I think I got a fair amount out of it.

After I was done with that, I thought I generally had the idea, but wanted to dive a little deeper into the language. So I read the Humble Little Ruby Book. I found the writing style a little distracting at times, but the book went beyond what I had learned with the ruby_koans, and after I was done I felt like I was ready to go. If you read this book, read the PDF version rather than the HTML version – the PDF one has much better code formatting (indents, etc.)

Ok, now that I was an expert in Ruby (ha), it was time to dive into Rails. Somehow I stumbled across the Ruby on Rails Tutorial by Michael Hartl. This was absolutely fantastic – I worked through it over a few days, and it provided a great foundation in Rails. I really can’t recommend this enough; he even covers rvm, git, rspec, heroku, and lots of other real-world topics. You can buy the book, buy a screencast version, or go through the free online version.

The beginning of that tutorial gave a little taste of using Git and Github; I realized I was going to need to learn a little more about git. To do this, I’ve been reading Pro Git by Scott Chacon, which seems like the go-to reference for git. You can read it online for free, or buy the book.

And then finally, as I’ve been working on a new project, I’ve been reading through the Rails Guides, a little at a time. They sort of pick up where the Ruby on Rails Tutorial leaves off, filling in details on specifics.

Hopefully this will be helpful for some folks…and I’m happy to finally have all these links in one place. If there are other great resources out there, please leave a comment and let me know!

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