feat: Enable support for `Regexp` patterns when subscribing to Active Support's instrumentation Events #1296

erichmachado · 2024-12-09T23:30:29Z

This PR aims to introduce support for Regexp patterns to the OpenTelemetry::Instrumentation::ActiveSupport.subscribe method.

This should be in line with a similar feature available on ActiveSupport::Notifications.subscribe.

With this update, users will be able to:

Subscribe to multiple events at once, if desired.
Use the Regexp pattern directly without having to resort to a custom span_name_formatter to work around crashes when processing the event name.
Process the incoming event name if span_name_formatter is set, since the name parameter in the initializer includes a reference to the Regexp pattern in this case.

…'s instrumentation Events

linux-foundation-easycla · 2024-12-09T23:30:33Z

The committers listed above are authorized under a signed CLA.

✅ login: erichmachado / name: Erich Soares Machado (b8c0fca, f541dfb, 835edc3, b1d707f)
✅ login: arielvalentin / name: Ariel Valentin (95223a8)

erichmachado · 2024-12-09T23:39:12Z

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

-    it 'does not trace an event by default' do
-      ActiveSupport::Notifications.subscribe(notification_name) do
-        # pass
+    describe 'when subscribing to events directly' do


The tests in this context are the same as before, I've just added one level of indentation.

erichmachado · 2024-12-09T23:40:03Z

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

+      ActiveSupport::Notifications.notifier.all_listeners_for(notification_name).each do |listener|
+        ActiveSupport::Notifications.unsubscribe(listener)
+      end


This prevents subscriptions from leaking across tests. Just using ActiveSupport::Notifications.unsubscribe with a Regexp won't work as intended.

erichmachado · 2024-12-09T23:40:59Z

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

-    it 'finishes spans even when complex subscribers blow up' do
-      ActiveSupport::Notifications.subscribe(notification_name, CrashingEndSubscriber.new)
-      OpenTelemetry::Instrumentation::ActiveSupport.subscribe(tracer, notification_name)
+    describe 'when subscribing to events matching a regular expression' do


This context contains the same tests as above, but exercising the pattern subscription.

arielvalentin · 2024-12-10T00:54:49Z

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

@@ -137,11 +138,20 @@ def sanitized_value(value)
          end
        end

+        def span_name(name)


I see what you meant now. Duping the string will now result in a separate string allocation and an additional case statement per subscription call. The difference in use between the regexp matcher and string based subscriber is only for span names right?

I think maybe it would be best in this case then to use the span name found on the payload and then keep the name instance variable as more as a indexing value that we can use to unsubscribe registrations or inspect the object to know what it's subscribed to but not use it for span naming. Does that help?

Thank you for your review @arielvalentin!

I think maybe it would be best in this case then to use the span name found on the payload and then keep the name instance variable as more as a indexing value that we can use to unsubscribe registrations or inspect the object to know what it's subscribed to but not use it for span naming. Does that help?

It does help. It's also a behavioural change, meaning this test will break:

opentelemetry-ruby-contrib/instrumentation/active_support/test/opentelemetry/instrumentation/active_support/span_subscriber_test.rb

Lines 38 to 41 in 7bda424

it 'memoizes the span name' do

span, = subscriber.start('oh.hai', 'abc', {})

_(span.name).must_equal(notification_name)

end

Which is the behaviour I was trying to preserve there. In this case, would it make sense to just remove that test?

I think that should be ok.

That test is a bit strange because I was guarding against the very unlikely bug that AS Notifications to invoke the subscriber with an event that it was not subscribed to.

You can probably delete it.

Thank you! I've updated that on b8c0fca. Can you please check if this is what you were looking for?

erichmachado · 2024-12-10T23:41:46Z

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

+      it 'finishes spans even when block subscribers blow up' do
+        # This scenario cannot be exercised reliably on Active Support < 7.0 since the #finish method
+        # will never be called by the notifier if another subscriber raises an error.
+        #
+        # See this PR for additional details: https://github.com/rails/rails/pull/43282
+        skip 'Notifications will be broken in this scenario on Active Support < 7.0' if ActiveSupport.version < Gem::Version.new("7.0")
+
+        ActiveSupport::Notifications.subscribe(notification_pattern) { raise 'boom' }
+        OpenTelemetry::Instrumentation::ActiveSupport.subscribe(tracer, notification_pattern)
+
+        expect do
+          ActiveSupport::Notifications.instrument(notification_name, extra: 'context')
+        end.must_raise RuntimeError
+
+        _(last_span).wont_be_nil
+        _(last_span.name).must_equal(notification_name)
+        _(last_span.attributes['extra']).must_equal('context')
+      end
+
+      it 'finishes spans even when complex subscribers blow up' do
+        # This scenario cannot be exercised reliably on Active Support < 7.0 since the #finish method
+        # will never be called by the notifier if another subscriber raises an error.
+        #
+        # See this PR for additional details: https://github.com/rails/rails/pull/43282
+        skip 'Notifications will be broken in this scenario on Active Support < 7.0' if ActiveSupport.version < Gem::Version.new("7.0")
+
+        ActiveSupport::Notifications.subscribe(notification_pattern, CrashingEndSubscriber.new)
+        OpenTelemetry::Instrumentation::ActiveSupport.subscribe(tracer, notification_pattern)
+
+        expect do
+          ActiveSupport::Notifications.instrument(notification_name, extra: 'context')
+        end.must_raise RuntimeError
+
+        _(last_span).wont_be_nil
+        _(last_span.name).must_equal(notification_name)
+        _(last_span.attributes['extra']).must_equal('context')
+      end


I had to skip these two tests on Active Support 6.1 since there's a bug in this version that prevents the subscriber from properly finishing the spans if another subscriber raises an error.

See rails/rails#43282 for further details.

…p-subscription

Enable support for Regexp patterns when subscribing to Active Support…

b1d707f

…'s instrumentation Events

erichmachado commented Dec 9, 2024

View reviewed changes

arielvalentin reviewed Dec 10, 2024

View reviewed changes

Stop memoizing the span name

b8c0fca

erichmachado force-pushed the em-feat-active-support-instrumentation-regexp-subscription branch 2 times, most recently from 6cf922f to 9791e56 Compare December 10, 2024 23:35

Ensure that tests pass on Active Support 6.1

835edc3

erichmachado force-pushed the em-feat-active-support-instrumentation-regexp-subscription branch from 9791e56 to 835edc3 Compare December 10, 2024 23:40

erichmachado commented Dec 10, 2024

View reviewed changes

Fix RuboCop offenses

f541dfb

erichmachado marked this pull request as ready for review December 11, 2024 19:31

erichmachado requested review from fbogsany, mwear, robertlaurin, dazuma, ericmustin, ahayworth, plantfansam, robbkidd, simi, kaylareopelle, xuan-cao-swi and a team as code owners December 11, 2024 19:31

Merge branch 'main' into em-feat-active-support-instrumentation-regex…

95223a8

…p-subscription

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feat: Enable support for `Regexp` patterns when subscribing to Active Support's instrumentation Events #1296

feat: Enable support for `Regexp` patterns when subscribing to Active Support's instrumentation Events #1296

erichmachado commented Dec 9, 2024 •

edited

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linux-foundation-easycla bot commented Dec 9, 2024 •

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erichmachado Dec 9, 2024

erichmachado Dec 9, 2024

erichmachado Dec 9, 2024

arielvalentin Dec 10, 2024

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arielvalentin Dec 10, 2024

erichmachado Dec 10, 2024

erichmachado Dec 10, 2024

	it 'memoizes the span name' do
	span, = subscriber.start('oh.hai', 'abc', {})
	_(span.name).must_equal(notification_name)
	end

feat: Enable support for Regexp patterns when subscribing to Active Support's instrumentation Events #1296

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feat: Enable support for `Regexp` patterns when subscribing to Active Support's instrumentation Events #1296

feat: Enable support for `Regexp` patterns when subscribing to Active Support's instrumentation Events #1296

erichmachado commented Dec 9, 2024 •

edited

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linux-foundation-easycla bot commented Dec 9, 2024 •

edited

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