✨ [RUM-3542] Add trace context injection control in rum configuration

[cy-moi]

Motivation

APM is working on building more granular sampling control on the backend side which can't be applied if the sampling decision is already taken on the client side.

Changes

Added a field traceContextInjection in the configuration to control context injection.

This new configuration allows more granular sampling at the backend and does not bring any break changes. It is available along with sampling rate configuration.

traceContextInjection is an opt-in configuration defaults to "all" which means no behavior changes. If opt-in for the "sampled" option, you would see only sampled requests having trace context attached to them.

Testing

Sampling Decision	traceContextInjection	Expected Behavior
Sampled	all	Inject trace context with sampling priority 1
Sampled	sampled	Inject trace context with sampling priority 1
Not Sampled	all	Inject trace context with sampling priority 0
Not Sampled	sampled	Do not inject trace context

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫%	Status
Rum	155.96 kB	156.17 kB	+0.14%	✅
Logs	55.15 kB	55.15 kB	0.00%	✅
Rum Slim	101.53 kB	101.74 kB	+0.21%	✅
Worker	25.21 kB	25.21 kB	0.00%	✅

[amortemousque]

FMU, the check should more look like this

 if (
    (context.traceSampled && configuration.traceContextInjection === TraceContextInjection.Sampled) ||
    configuration.traceContextInjection === TraceContextInjection.All
  ) {
    inject(makeTracingHeaders(context.traceId, context.spanId, context.traceSampled, tracingOption.propagatorTypes))
  }

[cy-moi]

Thank you! I updated this and added tests accordingly.

[BenoitZugmeyer]

💬 suggestion: ‏user-facing enums should be defined as a plain object, like so:

browser-sdk/packages/core/src/domain/configuration/configuration.ts

Lines 17 to 22 in c52216b

	export const DefaultPrivacyLevel = {
	ALLOW: 'allow',
	MASK: 'mask',
	MASK_USER_INPUT: 'mask-user-input',
	} as const
	export type DefaultPrivacyLevel = (typeof DefaultPrivacyLevel)[keyof typeof DefaultPrivacyLevel]

This allows using either the object (ex: TraceContextInjection.All) or the value directly (ex: "all") without facing typing issues, from JS or TS.

In any case, const enum should never be customer-facing because non-TS users won't have access to it.

[cy-moi]

Got it. I updated it with an object like this and moved it to the same configuration file.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.90%. Comparing base (734c28e) to head (2ecef9f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2656      +/-   ##
==========================================
- Coverage   92.91%   92.90%   -0.01%     
==========================================
  Files         239      239              
  Lines        6934     6939       +5     
  Branches     1517     1520       +3     
==========================================
+ Hits         6443     6447       +4     
- Misses        491      492       +1     

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[cy-moi]

/to-staging

[dd-devflow]

🚂 Branch Integration: starting soon, merge in < 10m

Commit ec7d3c5825 will soon be integrated into staging-12.

This build is going to start soon! (estimated merge in less than 10m)

Use /to-staging -c to cancel this operation!

[dd-devflow]

🚂 Branch Integration: This commit was successfully integrated

Commit ec7d3c5825 has been merged into staging-12 in merge commit a155b4d01e.

Check out the triggered pipeline on Gitlab 🦊

[bcaudan]

Nice!

[hong823]

@cy-moi Any idea if this would support when only using W3C propagatorTypes?

          allowedTracingUrls: [
            { match: "https://example.com", propagatorTypes: ['tracecontext'] }
          ]

From what I can tell, it might not be. Can you confirm?