fix: Don't scan profile events if listener is not set

[erezrokah]

Summary

Fixes #1685. A better way would be to be able to disable these events altogether from being returned to the client.

Also, if this PR is accepted we might want to do the same for other listeners, though I haven't seen a big issue with allocations in other places (see issue for memory profiles).

For the benchmark in the issue this is over a 3x improvement

Checklist

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG

[erezrokah]

Taking a look at the test failures 👀

[erezrokah]

I have some tests failing for me on main so hopefully #1687 fixes the issues?

[erezrokah]

Anything missing from the PR or from the issue? Is there another approach I should take? 3x improvement in memory allocations seems quite good. I can add more benchmarks/screenshots if needed

[Copilot]

Pull Request Overview

This PR optimizes memory allocation by skipping the scanning and processing of profile events when no profile event listener is registered. The change addresses a performance issue where profile events were being unnecessarily parsed even when the client wasn't interested in them, resulting in significant memory allocations.

Key changes:

• Modified profile event handling to conditionally scan events only when a listener is set
• Refactored onProcess initialization to conditionally set the profileEvents handler

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/issues/1685_test.go	Adds benchmark test to verify the performance improvement for the profile events optimization
context.go	Refactors onProcess() to conditionally assign profileEvents handler only when listener is present
conn_profile_events.go	Adds scanEvents parameter to skip event parsing when no listener is registered
conn_process.go	Updates profile events handling to pass scan flag and conditionally invoke handler

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[Copilot]

The scanEvents check on line 192 is redundant. When scanEvents is false, on.profileEvents is nil (as set in context.go), so calling it would panic. However, since profileEvents() already returns nil when scanEvents is false (line 28 of conn_profile_events.go), this condition will never execute with a nil handler. Remove this check and call on.profileEvents(events) unconditionally, relying on the nil check in context.go.

Suggested change

	if scanEvents {
	on.profileEvents(events)
	}
	on.profileEvents(events)

[erezrokah]

this condition will never execute with a nil handler

This is incorrect, if scanEvents is false on.profileEvents is nil and the call will panic (double checked by removing the condition and re-running the test)