feat: ActiveSupport user specified span kind

This will allow users to subscribe to notifications for Server Ingress, Messaging, or clients

See open-telemetry#957

instrumentation/active_support/lib/opentelemetry/instrumentation/active_support/span_subscriber.rb

@@ -19,13 +19,15 @@ def self.subscribe(
         tracer,
         pattern,
         notification_payload_transform = nil,
-        disallowed_notification_payload_keys = []
+        disallowed_notification_payload_keys = [],
+        kind = nil
       )
         subscriber = OpenTelemetry::Instrumentation::ActiveSupport::SpanSubscriber.new(
           name: pattern,
           tracer: tracer,
           notification_payload_transform: notification_payload_transform,
-          disallowed_notification_payload_keys: disallowed_notification_payload_keys
+          disallowed_notification_payload_keys: disallowed_notification_payload_keys,
+          kind: nil
         )
 
         subscriber_object = ::ActiveSupport::Notifications.subscribe(pattern, subscriber)
@@ -55,15 +57,16 @@ def self.subscribe(
       class SpanSubscriber
         ALWAYS_VALID_PAYLOAD_TYPES = [TrueClass, FalseClass, String, Numeric, Symbol].freeze
 
-        def initialize(name:, tracer:, notification_payload_transform: nil, disallowed_notification_payload_keys: [])
+        def initialize(name:, tracer:, notification_payload_transform: nil, disallowed_notification_payload_keys: [], kind: nil)
           @span_name = name.split('.')[0..1].reverse.join(' ').freeze
           @tracer = tracer
           @notification_payload_transform = notification_payload_transform
           @disallowed_notification_payload_keys = disallowed_notification_payload_keys
+          @kind = kind || :internal
         end
 
         def start(name, id, payload)
-          span = @tracer.start_span(@span_name, kind: :internal)
+          span = @tracer.start_span(@span_name, kind: @kind)
           token = OpenTelemetry::Context.attach(
             OpenTelemetry::Trace.context_with_span(span)
           )

instrumentation/active_support/test/opentelemetry/instrumentation/active_support/span_subscriber_test.rb

@@ -11,10 +11,12 @@
   let(:tracer) { instrumentation.tracer }
   let(:exporter) { EXPORTER }
   let(:last_span) { exporter.finished_spans.last }
+  let(:span_kind) { nil }
   let(:subscriber) do
     OpenTelemetry::Instrumentation::ActiveSupport::SpanSubscriber.new(
       name: 'bar.foo',
-      tracer: tracer
+      tracer: tracer,
+      kind: span_kind
     )
   end
 
@@ -76,6 +78,7 @@ def finish(name, id, payload)
     )
 
     _(last_span).wont_be_nil
+    _(last_span.kind).must_equal(:internal)
     _(last_span.attributes['string']).must_equal('keys_are_present')
     _(last_span.attributes['numeric_is_fine']).must_equal(1)
     _(last_span.attributes['boolean_okay?']).must_equal(true)
@@ -182,6 +185,24 @@ def finish(name, id, payload)
     end
   end
 
+  describe 'given a span kind' do
+    let(:span_kind) { :client }
+
+    it 'sets the kind on the span' do
+      span, token = subscriber.start('hai', 'abc', {})
+      # We only use the finished attributes - could change in the future, perhaps.
+      subscriber.finish(
+        'hai',
+        'abc',
+        __opentelemetry_span: span,
+        __opentelemetry_ctx_token: token
+      )
+
+      _(last_span).wont_be_nil
+      _(last_span.kind).must_equal(:client)
+    end
+  end
+
   describe 'instrument' do
     before do
       ActiveSupport::Notifications.unsubscribe('bar.foo')