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Scaffolding for building services
 Project Readme

roo_on_rails Gem Version Build Status Code Climate

roo_on_rails is:

  1. A library that extends Rails (as a set of Railties) and auto-configures common dependencies.
  2. A command that checks whether an application's Github repository and Heroku instanciations are compliant.

... packaged into a gem, to make following our guidelines easy.

Table of Contents

  • Installation
  • Library usage
    • Rack middleware
      • Disabling SSL enforcement
    • Database configuration
    • Sidekiq
    • Logging
    • Identity
    • Google OAuth authentication
    • Datadog Integration
      • Heroku metrics
      • Custom application metrics
    • API Authentication
  • Command features
    • Usage
    • Description
  • Contributing
  • License


Add this line at the top of your Rails application's Gemfile:

gem 'roo_on_rails'

Remove the following gems from your Gemfile, as they're provided and configured by roo_on_rails:

  • dotenv

Also remove any other gem-specific configuration from your repository.

And then execute:

$ bundle

Then re-run your test suite to make sure everything is shipshape.

Running specs

To run the specs locally, you will need to run the following command:

bundle config --local gemfile $PWD/gemfiles/<%= variant %>.gemfile

Where <%= variant %> is the Rails version you'd like to test (e.g. rails_5_2).

bundle exec rspec should then work as normal.

Library usage

Rack middleware

We'll insert the following middlewares into the rails stack:

  1. Rack::Timeout: sets a timeout for all requests. Use RACK_SERVICE_TIMEOUT (default 15) and RACK_WAIT_TIMEOUT (default 30) to customise.
  2. Rack::SslEnforcer: enforces HTTPS.
  3. Rack::Deflater: compresses responses from the application, can be disabled with ROO_ON_RAILS_RACK_DEFLATE (default: 'YES').
  4. Optional middlewares for Google Oauth2 (more below).

Disabling SSL enforcement

If you're running your application on Hopper, you'll need to turn off SSL enforcement as we do that at edge level in Cloudflare rather than the application code itself, which must be served over HTTP to its associated ALB, which handles SSL termination. To do this, you can set the ROO_ON_RAILS_DISABLE_SSL_ENFORCEMENT to YES.

Database configuration

The database statement timeout will be set to a low value by default. Use DATABASE_STATEMENT_TIMEOUT (milliseconds, default 200) to customise.

When using a PGBouncer, setting the timeout from the application will cause inconsistent results. The timeout should always be set using the RDS parameter group in thise case. To prevent the app trying to set a timeout, set DATABASE_STATEMENT_TIMEOUT to -1.

For database creation and migration (specifically the db:create, db:migrate, db:migrate:down and db:rollback tasks) a much higher statement timeout is set by default. Use MIGRATION_STATEMENT_TIMEOUT (milliseconds, default 10000) to customise.

Note: This configuration is not supported in Rails 3 and will be skipped. Set statement timeouts directly in the database.


Deliveroo services implement Sidekiq with an urgency pattern. By only having time-based SLA queue names (eg. within5minutes) we can automatically create incident alerting for queues which take longer than the time the application needs them to be processed.

When SIDEKIQ_ENABLED is set we'll:

  • check for the existence of a worker line in your Procfile;
  • add SLA style queues to your worker list;
  • check for a HIREFIRE_TOKEN and if it's set enable SLA based autoscaling;

The following ENV are available:

  • SIDEKIQ_QUEUES - comma-separated custom queue names; if not specified, default queues are processed which are defined here. For accurate health reporting and scaling for your custom queue names, you can specify their permitted latency within this variable e.g. within5seconds,queue-one:10seconds,queue-two:20minutes,queue-three:3hours,queue-four:1day,default. For non-default queue names that don't follow the withinXunit pattern, you will need to specify the permitted latency otherwise the initialization will error.
  • SIDEKIQ_THREADS (default: 25) - Sets sidekiq concurrency value
  • SIDEKIQ_DATABASE_REAPING_FREQUENCY (default: 10) - For sidekiq processes the amount of time in seconds rails will wait before attempting to find and recover connections from dead threads

NB. If you are migrating to SLA-based queue names, do not set SIDEKIQ_ENABLED to true before your old queues have finished processing (this will prevent Sidekiq from seeing the old queues at all).


For clearer and machine-parseable log output, the Rails logger is replaced by an extended logger to add context to your logs, which is output as logfmt key/value pairs along with the log message.

You can use the logger as usual:

Rails.logger.info { 'hello world' }

From your console, the output will include the timestamp, severity, and message:

[2017-08-25 14:34:54.899]    INFO | hello world

In production (or whenever the output isn't a TTY), the timestamp is stripped (as it's provided by the logging pipes) and the output is fully valid logfmt:

at=INFO msg="hello world"

One can also add context using the with method:

logger.with(a: 1, b: 2) { logger.info 'Stuff' }
# => at=INFO msg=Stuff a=1 b=2
logger.with(a: 1) { logger.with(b: 2) { logger.info('Stuff') } }
# => at=INFO msg=Stuff a=1 b=2
logger.with(a: 1, b: 2).info('Stuff')
# => at=INFO msg=Stuff a=1 b=2

See the class documentation for further details.


If your service wants to accept JWTs for identity claims, then setting the VALID_IDENTITY_URL_PREFIXES environment variable (to be a comma separasted list of the URL prefixes which valid JWTs come from) will set everything up, eg:


Any inbound request which has a valid JWT will have the claims made available:

class MyController
  def index
    customer_id = request.env['roo.identity']['cust']
    # => JSON::JWT

Be aware that maliciously crafted JWTs will raise 401s that your other middleware can present and poorly configured JWT set up will raise errors that you'll be able to catch in test.

Google OAuth authentication

When GOOGLE_AUTH_ENABLED is set to true we inject a Omniauth Rack middleware with a pre-configured strategy for Google Oauth2.


  • GOOGLE_AUTH_PATH_PREFIX (optional, defaults to /auth)
  • GOOGLE_AUTH_CONTROLLER (optional, defaults to sessions)

This feature is bring-your-own-controller — it won't magically protect your application.

A simple but secure example is detailed in README.google_oauth2.md.

Datadog Integration

Heroku metrics

To send system metrics to Datadog (CPU, memory usage, HTTP throughput per status, latency, etc), your application need to send their logs to the metrics bridge.

This is automatically configured when running roo_on_rails harness.

Custom application metrics

Sending custom metrics to Datadog through Statsd requires an agent running in each dyno or container. For Heroku you need to add the buildpack heroku-buildpack-datadog.

Once this is done, you can send metrics with e.g.:

RooOnRails.statsd.increment('my.metric', tags: ['tag:value'])

The following tags will automatically be added to all your metrics and their value depends on the environment variables listed below, in order of priority:

  • env:{name}
    • STATDS_ENV – optional and to be set manually (e.g. staging);
    • HOPPER_ECS_CLUSTER_NAME – automatically set by Hopper (e.g. staging);
    • Defaults to unknown.
  • source:{name}
    • DYNO – automatically set by Heroku (e.g. web.3);
    • HOSTNAME – automatically set by Hopper (e.g. 876c57c17207);
    • Defaults to unknown.
  • app:{name}
    • STATSD_APP_NAME – optional and to be set manually (e.g. notifications-staging);
    • HEROKU_APP_NAME – automatically set by Heroku (e.g. roo-notifications-staging);
    • HOPPER_APP_NAME+HOPPER_ECS_CLUSTER_NAME – automatically set by Hopper (e.g. notifications-staging);
    • Defaults to unknown.

API Authentication

RooOnRails provides a concern which will make adding rotatable API authentication to your service a breeze:

require 'roo_on_rails/concerns/require_api_key'

class ThingController < ActionController::Base
  include RooOnRails::Concerns::RequireApiKey

  # or
  require_api_key(only: :update)
  # or
  require_api_key(only_services: %i(service_1 service_2))

  def index
    # etc

Keys are specified in environment variables ending with _CLIENT_KEY, where the value is a comma separated list of keys which the specified service can authenticate with. This means that if your service has the environment variables:


Then, for any controller where this concern has been initiated, Basic Authentication will be required and only service_1:abc123abc123, service_1:def456def456 and service_2:I-never-could-get-the-hang-of-Thursdays will be allowed access.

Command features


Run the following from your app's top-level directory:

roo_on_rails harness

That command will sequentially run a number of checks. For it to run successfully, you will need:

  • a GitHub API token that can read your GitHub repository's settings placed in ~/.roo_on_rails/github-token
  • the Heroku toolbelt installed and logged in
  • admin privileges on the roo-dd-bridge-production (this will be addressed eventually)

The command can automatically fix most of the failing checks automatically; simply run it with the --fix flag:

roo_on_rails harness --fix

To run checks for only one environment, use the --env flag:

roo_on_rails harness --env staging


Running the roo_on_rails command currently checks for:

  • the presence of PLAYBOOK.md
  • compliant Heroku app naming;
  • presence of the Heroku preboot flag;
  • correct Github master branch protection;
  • integration with the Heroku-Datadog metrics bridge (for CPU, memory, request throughput data);
  • integration with Papertrail;
  • correct Sidekiq configuration.

The command is designed to fix issues in many cases.


Pull requests are welcome on GitHub at https://github.com/deliveroo/roo_on_rails.


  1. Bump the version number in `lib/roo_on_rails/version.rb
  2. Add an entry to the changelog
  3. After merging to master release e.g. bundle exec rake release


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