Serf::Handler

Serf (https://www.serf.io/) is a decentralized tool, by HashiCorp, for managing cluster membership, failure detection, and Orchestration. One of Serf's key features is the ability to issue queries and trigger events on other agents in the cluster. Serf can run arbitrary handlers in order to handle these queries and events.

This package encapsulates a small, simple library to facilitate writing flexible Serf handlers with Ruby. Also included in the package is a set of prebuilt handlers which can be used immediately in your own Serf cluster.

Usage

require 'serf/handler'

Serf::Handler.run

No additional code is necessary to implement a Serf handler. This basic implementation is available in bin/serf-handler.rb.

Specific query/event handlers are implemented as Ruby classes, by includeing Serf::Handler into your class. A very basic DSL is provided to aid implementation.

require 'serf/handler'
include Serf::Handler

describe "Provide a list of all available handlers."

on :query, 'list-handlers', 0 do |event|
  Serf::Handler::Tasks.collect do |task|
    "#{task.type}: #{task.name}\n"
  end.join
end

• describe: Attach a human readable description to whatever event is defined next.
• on: Takes two, or, optionally, three arguments (type, name, order) to describe the task, and a block that implements the task.

When a query or an event is received by the handler, it will run any tasks with a matching type that do not have a name, in an order described by sorting the tasks numerically on their order value. The default value for order, if not given, is 0. It will then run any named task or tasks with a matching name.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/wyhaines/serf-handler.

License

The gem is available as open source under the terms of the MIT License.