OpenTracing API for Ruby

This package is a Ruby platform API for OpenTracing.

Required Reading

In order to understand the Ruby platform API, one must first be familiar with the OpenTracing project and terminology more specifically.

Installation

Add this line to your application's Gemfile:

gem 'opentracing'

And then execute:

$ bundle

Or install it yourself as:

$ gem install opentracing

Usage

Everyday consumers of this opentracing gem really only need to worry about a couple of key abstractions: the start_span function, the Span interface, and binding a Tracer at runtime. Here are code snippets demonstrating some important use cases.

Singleton initialization

As early as possible, call

require 'opentracing'
OpenTracing.global_tracer = MyTracerImplementation.New(...)

Where MyTracerImplementation is your tracer. For testing, you can use the provided OpenTracing::NilTracer

Non-Singleton initialization

If you prefer direct control to singletons, manage ownership of the Tracer implementation explicitly.

Starting an empty trace by creating a "root span"

It's always possible to create a "root" Span with no parent or other causal reference.

span = OpenTracing.start_span("operation_name")
span.finish

This example will start a span on the global tracer (initialized above). If you are managing your own tracer you'll need to call start_span on your tracer.

Creating a (child) Span given an existing (parent) Span

span = OpenTracing.start_span("parent")
child = OpenTracing.start_span("child", child_of: span)
child.finish
span.finish

Serializing to the wire

Using Net::HTTP:

client = Net::HTTP.new("myservice.com")
req = Net::HTTP::Post.new("/")

span = OpenTracing.start_span("my_span")
OpenTracing.inject(span.context, OpenTracing::FORMAT_RACK, req)
res = client.request(req)
#...

Using Faraday middleware:

class TraceMiddleware < Faraday::Middleware
  def call(env)
    span = OpenTracing.start_span("my_span")
    OpenTracing.inject(span.context, OpenTracing::FORMAT_RACK, env)
    @app.call(env).on_complete do
      span.finish
    end
  end
end

Deserializing from the wire

The OpenTracing Ruby gem provides a specific Rack header extraction format, since most Ruby web servers get their HTTP Headers from Rack. Keep in mind that Rack automatically uppercases all headers and replaces dashes with underscores. This means that if you use dashes and underscores and case-sensitive baggage, it will not be possible to discern once Rack has processed it.

class MyRackApp
  def call(env)
    extracted_ctx = @tracer.extract(OpenTracing::FORMAT_RACK, env)
    span = @tracer.start_span("my_app", child_of: extracted_ctx)
    span.finish
    [200, {}, ["hello"]]
  end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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 tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/opentracing/opentracing-ruby. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

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