Health check page as Rack middleware
Latest commit 55ee6a0 Oct 23, 2016 @createdbypete createdbypete committed on GitHub Merge pull request #3 from taoza/fix_migration_version_check
Fix result set data type issue by selecting the value directly.


An easy to configure Rack middleware for Ruby web apps to provide a simple health check endpoint that tells you vital life signs about your app. All without the boilerplate service checking code you've written 10 times before.

(it's ECG as in electrocardiogram - as in the machine that monitors how your heart works)


  • simple 1 line to drop into your or config/application.rb file to set up
  • reports git revision status
  • reports ActiveRecord migration schema version
  • reports errors if any check can't be executed for whatever reason
  • JSON output

Development Status travis ci build

Rack::ECG is extracted from production code in use at Envato. However, it is undergoing early development, and APIs and features are almost certain to be in flux.

Getting Started

Add this line to your application's Gemfile:

gem 'rack-ecg'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-ecg


In Rails you can add Rack::ECG to your config/application.rb as a middleware

# config/application.rb
# ...
config.middleware.use Rack::ECG
# ...


In Rack apps, you can add Rack::ECG to your

require 'rack/ecg'

use Rack::ECG

run MyRackApp

You can now hit your app and get a basic health check response from Rack::ECG

$ curl http://localhost:9292/_ecg
  "http": {
    "status": "ok",
    "value": "online"

/_ecg will return a 200 HTTP status if all the checks are OK, or 500 status if any of the checks fail.


There are options that can be passed to use Rack::ECG to customise how it works.


Out of the box Rack::ECG doesn't do much and just checks that HTTP responses can be returned. There are a number of built in checks that Rack::ECG can be told to do (more to come)

  • :git_revision - this assumes your code is deployed via git and exists in a git repo, and that the git command can access it
  • :migration_version - this assumes you are using ActiveRecord migrations. It queries the schema_versions table and tells you what version the database is at.

So using git_revision and migration_version would look like:

use Rack::ECG, checks: [:git_revision, :migration_version]
$ curl http://localhost:9292/_ecg
  "http": {
    "status": "ok",
    "value": "online"
  "git_revision": {
    "status": "ok",
    "value": "fb16e2c3b88af671c42880e6977bba34d7b05ba6\n"
  "migration_version": {
    "status": "ok",
    "value": "20150319050250"


By default Rack::ECG is mapped to a URL of /_ecg, you can set this to a different path by setting the at option. e.g.

use Rack::ECG, at: "/health_check"

More examples are provided in /examples


  • Ruby >= 1.9.3 (this may be increased to Ruby >= 2.0 if it makes sense to use Ruby 2.0 features)
  • Rack
  • To use optional git_revision check, your deployed code needs to be in a git repo, and git command must be accessible on the server
  • To use optional migration_version check, you must be using ActiveRecord and migrations stored in schema_versions table





Rack::ECG uses MIT license. See LICENSE.txt for details.

Code of conduct

We welcome contribution from everyone. Read more about it in


For bug fixes, documentation changes, and small features:

  1. Fork it ([my-github-username]/rack-ecg/fork )
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

For larger new features: Do everything as above, but first also make contact with the project maintainers to be sure your change fits with the project direction and you won't be wasting effort going in the wrong direction.


This project is maintained by the Envato engineering team and funded by Envato.

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Encouraging the use and creation of open source software is one of the ways we serve our community. See our other projects or come work with us where you'll find an incredibly diverse, intelligent and capable group of people who help make our company succeed and make our workplace fun, friendly and happy.