FileBasedHealthcheck

A gem to use a healthcheck for readiness and liveness probes in Kubernetes.

Installation

Add this line to your application's Gemfile:

gem 'file-based-healthcheck'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install file-based-healthcheck

Usage

The idea behind this gem is to register heartbeats using a file. Thanks to that and comparing when the last heartbeat, happened you can easily check if the process is running or not.

Initialize a new healthcheck:

healthcheck = FileBasedHealthcheck.new(directory: Rails.root.join("tmp"), filename: ENV.fetch("HOSTNAME"), time_threshold: 60)

Register a heartbeat:

healthcheck.touch

To verify if the process is running:

healthcheck.running?

This method is going to return true if the file (based on filename) was touched in the last time_threshold in seconds.

To remove file:

healthcheck.remove

It is recommended to implement some sort of wrapper for your processes and use this gem under the hood. Then, you could create a following binary:

#!/usr/bin/env ruby

require "bundler/setup"
require_relative "../lib/my_process"

result = MyProcess::HealthCheck.check
if result.success?
  exit 0
else
  MyProcess.logger.fatal "[MyProcess] health check failed: #{result.message}"
  exit 1
end

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 the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/file-based-healthcheck.

License

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