Kubernetes::Health

This gem allows kubernetes monitoring your app while it is running migrates and after it started.

Features

• add routes /_readiness and /_liveness on rails stack by default.
• allow custom checks for /_readiness and /_liveness on rails stack.
• add routes /_readiness and /_liveness while rake db:migrate runs. (optional).

Installation

Add this line to your application's Gemfile:

gem 'kubernetes-health', '~> 2.0'

Enabling monitoring while rake db:migrate runs

Your Dockerfile's entry script needs to run migrates before start your web app.

Add KUBERNETES_HEALTH_ENABLE_RACK_ON_MIGRATE=true environment variable.

or add in your application.rb.

    # default: false
    Kubernetes::Health::Config.enable_rack_on_migrate = true

In Kubernetes you need to configure your deployment readinessProbe like this:

    livenessProbe:
        httpGet:
        path: /_liveness
        port: 80
        initialDelaySeconds: 10
        timeoutSeconds: 5
    readinessProbe:
        httpGet:
        path: /_readiness
        port: 80
        initialDelaySeconds: 10
        timeoutSeconds: 5

How rake db:migrate monitoring works

It will run a RACK server for /_readiness and /_liveness routes while a rake db:migrate is running.

Customizing checks

It only works for routes in rails stack, they are not executed while rake db:migrate runs.

Ex. Check if PostgreSQL is reachable. params is optional.

Kubernetes::Health::Config.ready_if = lambda { |params|
    ActiveRecord::Base.connection.execute("SELECT 1").cmd_tuples != 1
}

Kubernetes::Health::Config.live_if = lambda { |params|
    ActiveRecord::Base.connection.execute("SELECT 1").cmd_tuples != 1
}

Customizing routes

Kubernetes::Health::Config.route_liveness = '/liveness'
Kubernetes::Health::Config.route_readiness = '/readiness