fix(go): filter out non-genkit traces from dev ui

[DEVMANISHOFFL]

Description

This PR addresses the issue where the Dev UI becomes cluttered with internal HTTP traces (e.g., standard net/http client calls) that are not relevant to the developer's AI flows.

I implemented a filteringExporter middleware for the OpenTelemetry TracerProvider. This ensures that only spans explicitly containing genkit attributes are exported to the Dev UI, filtering out background noise while preserving all relevant AI traces.

Issues Resolved

Fixes #3984

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually verified in Dev UI that extraneous HTTP GET traces are gone)
• Docs updated (not applicable, internal fix)

[gemini-code-assist]

Summary of Changes

Hello @DEVMANISHOFFL, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a usability issue in the Dev UI where internal HTTP traces were cluttering the display, making it difficult to focus on relevant AI flow traces. The solution involves introducing a filtering layer for OpenTelemetry spans, ensuring that only traces directly related to genkit operations are processed and displayed, thereby enhancing the clarity and utility of the Dev UI for developers.

Highlights

• Filtering OpenTelemetry Traces: A new filteringExporter has been introduced to selectively export OpenTelemetry spans, ensuring only relevant traces are processed.
• Improved Dev UI Clarity: This exporter specifically filters for spans containing genkit attributes, significantly reducing clutter from irrelevant internal HTTP traces in the Dev UI.
• Integration with TracerProvider: The filteringExporter is now integrated into both immediate and batch telemetry writing processes by wrapping the existing TelemetryServerExporter.

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[gemini-code-assist]

Code Review

This pull request introduces a filteringExporter to filter out non-genkit traces from the dev UI, which is a great improvement for reducing noise. The implementation is clear and effectively solves the issue. I've added a couple of suggestions to improve performance and maintainability by pre-allocating a slice and using an existing constant instead of a magic string. Overall, this is a solid contribution.

[gemini-code-assist]

For better performance and to avoid potential reallocations within the loop, it's a good practice to pre-allocate the slice with a known capacity. This ensures that the backing array for the slice is allocated only once.

Suggested change

	var genkitSpans []sdktrace.ReadOnlySpan
	genkitSpans := make([]sdktrace.ReadOnlySpan, 0, len(spans))

[gemini-code-assist]

To improve maintainability and avoid magic strings, please use the existing attrPrefix constant instead of the hardcoded string "genkit".

Suggested change

	if strings.HasPrefix(string(attr.Key), "genkit") {
	if strings.HasPrefix(string(attr.Key), attrPrefix) {

[DEVMANISHOFFL]

@google-gemini-code-assist Thanks for the review!

I have applied the suggested fixes:

• Removed unused imports in go/MIDDLEWARE.md.
• Fixed the typo in go/README.md.
• Applied the slice pre-allocation optimization in go/core/tracing/tracing.go.

Note on CI:
The tests are failing in go/ai (TestResolveFormat), which I have not touched. go vet ./core/... and go test ./core/... pass cleanly locally.

[gemini-code-assist]

Thanks for the update, @DEVMANISHOFFL! I appreciate you addressing the suggestions.

Regarding the CI failure in go/ai (TestResolveFormat), since you haven't touched that part of the codebase, it's likely an unrelated issue. It might be a pre-existing flake or an issue introduced by another change. Could you please check if this failure is new to this PR or if it's reproducible on main? My review focused on the changes introduced in this pull request, and this CI issue appears to be external to those modifications.

Let me know if you need any further assistance!