Write a README, and tweak the API a bit

README.md

@@ -1,35 +1,39 @@
-# DegicaDatadog
+# Degica Datadog
 
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/degica_datadog`. To experiment with that code, run `bin/console` for an interactive prompt.
-
-TODO: Delete this and the text above, and describe your gem
-
-## Installation
-
-Add this line to your application's Gemfile:
-
-```ruby
-gem 'degica_datadog'
-```
-
-And then execute:
-
-    $ bundle install
-
-Or install it yourself as:
-
-    $ gem install degica_datadog
+Internal library for StatsD and tracing.
 
 ## Usage
 
-TODO: Write usage instructions here
+1. Grab the gem from GitHub:
+    ```ruby
+    gem 'degica_datadog', git: 'https://github.com/degica/degica_datadog.git', branch: 'main'
+    ```
+1. Set the `SERVICE_NAME` environment variable to the name of your service.
+1. Then add this to your `config/application.rb` to enable tracing:
+    ```ruby
+    require "degica_datadog"
 
-## Development
+    DegicaDatadog::Tracing::init
+    ```
 
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+### Tracing
 
-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 the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+The setup above auto-instruments many components of the system, but you can add additional spans or span tags:
 
-## Contributing
-
-Bug reports and pull requests are welcome on GitHub at https://github.com/sulami/degica_datadog.
+```ruby
+# Create a new span.
+DegicaDatadog::Tracing::span!("hats.process_payment") do
+  # Process a payment.
+end
+
+tags = {
+    "merchant_uuid" => merchant.uuid,
+    "merchant_name" => merchant.name,
+}
+
+# Add tags to the current span.
+DegicaDatadog::Tracing::span_tags!(**tags)
+
+# Add tags to the current root span.
+DegicaDatadog::Tracing::root_span_tags!(**tags)
+```

lib/degica_datadog/tracing.rb

@@ -51,7 +51,7 @@ def span_tags!(**tags)
 
       # Please don't use this. It's just a temporary thing until we can get the
       # statsd agent installed
-      def add_tags_to_root_span!(**tags)
+      def root_span_tags!(**tags)
         return unless Config.enabled?
 
         # forgive me my friends