FileBasedHealthcheck

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

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

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

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.

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

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