BlueGreenWorkers

This gem provides helpers to coordiante workers across multiple clusters that for which only one cluster should be active at a time. Think blue green deployments

Installation

  gem 'blue_green_workers'

And then execute:

$ bundle

Or install it yourself as:

$ gem install blue_green_workers

Usage

This gem doesn't attempt to provide an interface through which you specify which cluster is currently active, that's left as an exercise to the reader. One could very easily use ActiveRecord and a simple RESTFul interface to set the current active cluster.

Config

BlueGreenWorkers.configure do |config|
  config.cluster_name = 'blue'
  config.determine_active_cluster { ActiveCluster.first.value }
  config.refresh_interval = 10
  config.activate { QueueClient.listen! }
  config.deactivate { QueueClient.shutdown! }
  config.logger = Logger.new STDOUT
end

• cluster_name - Defines the name for this cluster. Something like ENV['CLUSTER_NAME'] probably makes sense
• determine_active_cluster - Takes a block that returns the name of the current active cluster
• refresh_interval (optional) - How often to cache the active cluster in seconds, 0 (the default) will call the block passed to determine_active_cluster every time a worker is executed.
• activate (optiona) - Block to call when this cluster goes active. Will be called during initialization. refresh_interval must be specified.
• deactivate (optiona) - Block to call when this cluster goes passive. This block will not be called if the cluster is started in passive mode. refresh_interval must be specified.
• logger (optiona) - Logger to use

Executing jobs

In addition to attaching event handles to activate and deactivate you can also do this:

loop do
  BlueGreenWorkers.when_active(opts) do
    # Do some work, poll for stuff, etc
  end
  sleep 60
end

Options include:

• delay -- Delay for n seconds if we're not the active cluster
• return -- What to return if we're not the active cluster

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/hawknewton/blue_green_workers.