Monthly Archives: November 2009

Integrating Zeus ZXTM Load Balancer and Capistrano for Ruby on Rails websites

Posted by dansketcher on November 30, 2009
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At TouchLocal, one of the difficulties in automating deployment was the tight coupling between the app servers that were currently running and what the Load Balancer said was running. The implication of this is that at deployment time a human had to go into the ZXTM interface and update the list of running nodes before and afterwards. To ease this, and allow fully automatic deployment of Ruby on Rails apps running under Phusion Passenger, I built the ZXTMManager class.

This class implements an interface to the Zeus ZXTM API, allowing (in its current state) the ability to programatically change active nodes and manage other details of the commonly changed data in the Load Balancer. On top of that, there is an included deploy.rb file that shows the deployment recipes that can be simply and easily added to your own Capistrano configuration to use this class quickly and easily.

Enjoy.

Using DataFabric to replace Masochism

Posted by dansketcher on November 25, 2009
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When we upgraded from Rails 1.x to 2.x, we also had to migrate from Masochism to DataFabric. Unfortunately, the DataFabric way of doing things requires adding a declaration to each of the model classes. For a site like TouchLocal, where there are literally hundreds of model classes, this was a daunting task.

I’ve just gone through extracting the magic that makes it possible to do this programatically, released as DataFabric::Initializer. I hope it helps someone other than me!

Howto recover lost commits from a git rebase

Posted by dansketcher on November 23, 2009
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Yesterday, I was working on a branch of a branch in a git repository, and I wanted to merge the last branch back to master. Following chapter 3.6 of ProGit, I ran

git rebase --onto master branch1 branch2

Unfortunately for me, I seem to have either done it from the wrong place or done the wrong thing for my situation, because git rewound branch2 to the revision that it was branched from master and all the later commits were inaccessible!

However, I was not going to give up quite so easily, and I figured that once a revision was committed, it had to be somewhere.. Fortunately for me, I manged to find this post on how to recover lost commits in a git repository – I subsequently ran:

git reflog show
# find the commit with the last set of changes in your branch - 
# good commit comments are so useful!
git co b6654bd
git co -b branch2_2

With my branch recovered, I did a simple rebase of the new (old) branch onto master and merged it, and all was well.

Workling support for Synchronous AMQP RabbitMQ Clients and Amazon SQS Queues

Posted by dansketcher on November 16, 2009
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As a part of contracting work I have been doing for TouchLocal, I have just opensourced some code I wrote to support new Workling clients. As you may know, Workling is a Rails-oriented system for performing asynchronous processing and optionally returning data from these background workers. However, because of the implementation of the original AMQP client, you could not use RabbitMQ queues from non-evented Mongrel or Phusion Passenger servers (only evented Mongrel or Thin).

Building on the work of celdee-bunny and famoseagle-carrot, I implemented a RabbitMQ workling client that could be used from within Phusion Passenger and Mongrel. The Synchronous AMQP Workling client allows RabbitMQ to be used from Workling without requiring complicated changes to deployment scenarios. Also, I implemented the Return Store functionality, so that RabbitMQ users can get data back from the workers, just like when using Starling.

Additionally, it was useful at the time to add support for an Amazon SQS Workling client, more as an exercise in testing its performance than anything else. As with the SyncAmqpClient, support for the Return Store is present. One of the discoveries in working with Amazon SQS (via the RightAws gem) was the discovery that the default key structure for Workling (which uses colon characters for segment delimiters) is not supported by Amazon. As a result, if you define the keys used for AWS configuration, even if you don’t use them, they will change the Workling key structure. This is not a problem for new implementations, but for existing deployments adding this will mean that Workling cannot see the old queues and you may not be able to access them without removing the AWS configuration… not a deal breaker, but something to be aware of.

So, the TouchLocal github account holds the version of Workling that has these two implementation for now, at least until my pull request to the main branch is accepted :)

touchlocal-openx gem released

Posted by dansketcher on November 04, 2009
gems, hosting, Rails, software development / No Comments

After the last post, I spent a bit of time integrating my work (along with other upgrades) into a fork of the openx code on github and have released a gem version of it on GemCuttter.org

As you may or may not know, GemCutter.org will be the new default gem source by becoming rubygems.org. This is pretty exciting, because previously you had to have you project registered on rubygems.org in order to publish to it, or use the non-standard github gem host. Good stuff.

In any case, the new OpenX gem can be installed now by executing

sudo gem install touchlocal-openx --source "http://gemcutter.org"

# Load it using
require 'rubygems'
gem 'touchlocal-openx' 
require 'openx'

In Rails, include it like this in your Rails::Initializer block:

  config.gem "touchlocal-openx", :lib => "openx", :source => "http://gemcutter.org"

I’m a proud parent!