♻️ [RUM-958] Use a performance observable instead of the lifecycle

[amortemousque]

Motivation

The performanceCollection has too many concerns and limitations:

• it forces us to set a central configuration, while sometimes we might want to have slightly different options (ex here for durationThreshold)
• we always listen for every performance entries while in some cases it might not be needed (ex for longtask)
• we cannot use takeRecords() because the observer is centralized and it would take records for all types

The goal of this PR is to be able to use separate performance observer for each entry type:

• The first iteration uses a performanceObservable for performanceResourceTimings
• The next iteration will use it for other types of performance

Changes

• Introduce a lightweight performanceObservable which removes the performanceObservable fallback
• Move retrieveInitialDocumentResourceTiming from performanceCollection.ts in /domain/resource/retrieveInitialDocumentResourceTiming.ts
• Use the performanceObservable to collect performance resource
• Use the performanceObservable in waitPageActivityEnd

Testing

• [x] Local
• [ ] Staging
• [x] Unit
• [ ] End to end

---

I have gone over the contributing documentation.

[cit-pr-commenter[bot]]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	160.25 KiB	160.86 KiB	626 B	+0.38%	✅
Logs	57.91 KiB	57.91 KiB	4 B	+0.01%	✅
Rum Slim	108.77 KiB	109.39 KiB	626 B	+0.56%	✅
Worker	25.21 KiB	25.21 KiB	0 B	0.00%	✅

🚀 CPU Performance

| Action Name | Base Average Cpu Time (ms) | Local Average Cpu Time (ms) | 𝚫 | | --- | --- | --- | --- | | addglobalcontext | 0.001 | 0.002 | 0.001 | | addaction | 0.030 | 0.043 | 0.013 | | adderror | 0.032 | 0.044 | 0.013 | | addtiming | 0.001 | 0.001 | 0.000 | | startview | 0.893 | 1.020 | 0.127 | | startstopsessionreplayrecording | 0.771 | 0.974 | 0.203 | | logmessage | 0.020 | 0.026 | 0.006 |

🧠 Memory Performance

| Action Name | Base Consumption Memory (bytes) | Local Consumption Memory (bytes) | 𝚫 (bytes) | | --- | --- | --- | --- | | addglobalcontext | 22.20 KiB | 20.92 KiB | -1308 B | | addaction | 71.94 KiB | 71.11 KiB | -849 B | | adderror | 88.93 KiB | 86.31 KiB | -2681 B | | addtiming | 21.90 KiB | 19.44 KiB | -2520 B | | startview | 314.64 KiB | 334.02 KiB | 19.38 KiB | | startstopsessionreplayrecording | 13.51 KiB | 15.01 KiB | 1.50 KiB | | logmessage | 72.84 KiB | 70.91 KiB | -1979 B |

🔗 RealWorld

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.35484% with 7 lines in your changes missing coverage. Please review.

Project coverage is 93.64%. Comparing base (c48a9bd) to head (96c47cc).

Files	Patch %	Lines
...s/rum-core/test/emulate/mockPerformanceObserver.ts	87.87%	4 Missing :warning:
...ages/rum-core/src/browser/performanceObservable.ts	95.55%	2 Missing :warning:
...ages/rum-core/src/browser/performanceCollection.ts	85.71%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2818 +/- ## ========================================== + Coverage 93.31% 93.64% +0.32% ========================================== Files 263 266 +3 Lines 7482 7548 +66 Branches 1669 1679 +10 ========================================== + Hits 6982 7068 +86 + Misses 500 480 -20 ```

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[amortemousque]

/to-staging

[dd-devflow[bot]]

:steam_locomotive: Branch Integration: starting soon, median merge time is 0s

Commit 96c47cc4f5 will soon be integrated into staging-27.

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

[dd-devflow[bot]]

:steam_locomotive: Branch Integration: This commit was successfully integrated

Commit 96c47cc4f5 has been merged into staging-27 in merge commit ae24d645c0.