Configurable controller and action default tags

Author: liaden

README.md

@@ -76,6 +76,16 @@ end
 ```
 `append_info_to_payload` is a method from [ActionController::Instrumentation](https://api.rubyonrails.org/classes/ActionController/Instrumentation.html#method-i-append_info_to_payload)
 
+## Default tags: controller/action
+
+```
+Yabeda::Rails.enable_controller_action_default_tags = true
+```
+
+Other metrics that are generated while handing a request will include a tag for the controller and the action that we being handled. This works well with other yabeda gems like [yabeda-http_requests](https://github.com/yabeda-rb/yabeda-http_requestshttps://github.com/yabeda-rb/yabeda-http_requests).
+
+Due to the potential for high cardinality, this feature is disabled by default.
+
 
 ## Development
 

lib/yabeda/rails.rb

@@ -21,10 +21,19 @@ def on_controller_action(&block)
         controller_handlers << block
       end
 
+      attr_accessor :enable_controller_action_default_tags
+
       # Declare metrics and install event handlers for collecting themya
       # rubocop: disable Metrics/MethodLength, Metrics/BlockLength, Metrics/AbcSize
       def install!
         Yabeda.configure do
+          if enable_controller_action_default_tags
+            ::ActionController::Metal.prepend(::Yabeda::Rails::ActionControllerTags)
+
+            default_tags :controller, ""
+            default_tags :action, ""
+          end
+
           group :rails
 
           counter   :requests_total,   comment: "A counter of the total number of HTTP requests rails processed.",

lib/yabeda/rails/action_controller_tags.rb

@@ -0,0 +1,11 @@
+module Yabeda
+  module Rails
+    module ActionControllerDefaultTags
+      def process_action(*args)
+        Yabeda.with_tags(controller: controller_name, action: action_name) do
+          super
+        end
+      end
+    end
+  end
+end