feat: suppress internal spans with Faraday instrumentation (#1506)

* add flag to suppress downstream instrumentation

* update README

* change flag name

* fix README

Author: ezhang6811

instrumentation/faraday/README.md

@@ -18,7 +18,9 @@ To install the instrumentation, call `use` with the name of the instrumentation.
 
 ```ruby
 OpenTelemetry::SDK.configure do |c|
-  c.use 'OpenTelemetry::Instrumentation::Faraday'
+  c.use 'OpenTelemetry::Instrumentation::Faraday', {
+    enable_internal_instrumentation: false
+  }
 end
 ```
 
@@ -30,6 +32,11 @@ OpenTelemetry::SDK.configure do |c|
 end
 ```
 
+### Configuration options
+This instrumentation offers the following configuration options: 
+* `enable_internal_instrumentation` (default: `false`): When set to `true`, any spans with 
+ span kind of `internal` are included in traces.
+
 ## Examples
 
 Example usage of faraday can be seen in the [`./example/faraday.rb` file](https://github.com/open-telemetry/opentelemetry-ruby-contrib/blob/main/instrumentation/faraday/example/faraday.rb)

instrumentation/faraday/lib/opentelemetry/instrumentation/faraday/instrumentation.rb

@@ -28,6 +28,7 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
 
         option :span_kind, default: :client, validate: %i[client internal]
         option :peer_service, default: nil, validate: :string
+        option :enable_internal_instrumentation, default: false, validate: :boolean
 
         private
 

instrumentation/faraday/lib/opentelemetry/instrumentation/faraday/middlewares/tracer_middleware.rb

@@ -40,7 +40,13 @@ def call(env)
               ) do |span|
                 OpenTelemetry.propagation.inject(env.request_headers)
 
-                app.call(env).on_complete { |resp| trace_response(span, resp.status) }
+                if config[:enable_internal_instrumentation] == false
+                  OpenTelemetry::Common::Utilities.untraced do
+                    app.call(env).on_complete { |resp| trace_response(span, resp.status) }
+                  end
+                else
+                  app.call(env).on_complete { |resp| trace_response(span, resp.status) }
+                end
               rescue ::Faraday::Error => e
                 trace_response(span, e.response[:status]) if e.response