Adding support for collecting cross-platform perf traces and generating PGO JIT traces

[kshyju]

Enable cross-platform performance trace collection and PGO JIT trace generation.

1. Introduced a Node.js HTTP application to the test matrix for performance trace collection. This app is disabled by default, but can be enabled when running the pipeline.
2. Added a pipeline stage to merge and deduplicate JIT traces generated from multiple applications (currently supporting three apps).

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
  • Otherwise: Link to backporting PR
• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

[safihamid]

Looking at specialization urls for Flex we do need a call to /admin/instance/assign as well to include in PGO.

Here are all the calls to the Host during cold start and specialization:

url
'GET', 'userAgent': 'Go-http-client/1.1', 'uri': '/api/warmup' }
'POST', 'userAgent': 'NestedNodeAgent...'', 'uri': '/admin/instance/assign' }
'GET', 'userAgent': 'RunnersV3 Functions_ColdSite....', 'uri': '/api/hellohttp' }

Looks like we are doing 1 and 3 but not 2

[kshyju]

/admin/instance/assign

Looking at specialization urls for Flex we do need a call to /admin/instance/assign as well to include in PGO.

Here are all the calls to the Host during cold start and specialization:

url 'GET', 'userAgent': 'Go-http-client/1.1', 'uri': '/api/warmup' } 'POST', 'userAgent': 'NestedNodeAgent...'', 'uri': '/admin/instance/assign' } 'GET', 'userAgent': 'RunnersV3 Functions_ColdSite....', 'uri': '/api/hellohttp' }

Looks like we are doing 1 and 3 but not 2

I reviewed the code for the admin/instance/assign endpoint and want to understand which code paths are actually executed during specialization in PROD. I’m also curious if the same paths apply to other Linux Consumption SKUs. This will help me replicate the right environment setup in lab runs.

I'll handle that setup in a separate change to keep this PR focused and easier to review. It will also involve modifying the placeholder simulation logic — for example, this line needs to be removed, since the code only checks for the existence of the environment variable, not whether its value is "1".

[safihamid]