qs-request-tracker

Qs::Request::Tracker

Manages a Request-Id for each HTTP request. Hooks transparently into Faraday and service-client to pass request ids on to subsequent calls to other services. This way errors can be tracked through all layers and apps of your infrastructure easily.

Use as a Rack middleware

The easiest way to add request ids to your system is to add the Qs::Request::Tracker::Middleware as a middleware to your app.

require 'qs/request/tracker'

Rack::Builder.new do
  use Qs::Request::Tracker::Middleware
  run YourApp.new
end

This will add the request id to the response. If there is no Request-Id HTTP header set in the request it will also set that. Please note that all middlewares that are included before it will not have that header set!

Use the Faraday middleware

If you are using Faraday you transparently add the request id to all outgoing HTTP calls, too.

require 'faraday'
# make sure to require this middleware after faraday itself
require 'qs/request/tracker/faraday_middleware'

conn = Faraday.new(:url => 'http://example.com') do |faraday|
  # it is important to have the request_id middleware inserted before any Faraday adapter
  faraday.request :request_id
end

All requests done by that connection will now have a Request-Id http header set that equal the one from the request that came into your system. If this is used not within a request context that header will just not get set.

Imporant: This feature relies on thread local variables and will not work if you deal with more than one request per thread at a time!

This approach is inspired by Andy's talk on debugging large scale systems.

Use the service-client extension

This extension will automatically use the Faraday middleware for service-client connections that use the Service::Client::Adapter::Faraday adapter.

require 'service-client'
# make sure to require this extension after service-client itself
require 'qs/request/tracker/service_client_extension'

client = Service::Client.new('http://example.com/')
client.urls.add(:root, :get, "/")
client.get(client.urls.root, oauth_token)

This will then heave the Request-Id http header set through the Faraday middleware.