♻️ Refactor startSessionManager to return a Promise instead of using a callback

[thomas-lebeau]

Motivation

The startSessionManager function used a callback pattern (onReady) to signal when the session manager was initialized. This is unnecessary complexity since the function already operates asynchronously -- a Promise-based API is more idiomatic and easier to compose.

Changes

• Change startSessionManager to return Promise<SessionManager | undefined> instead of accepting an onReady callback
• Returns undefined when no session store strategy is configured (instead of never calling the callback)
• Update preStartLogs and preStartRum to await the session manager instead of using callbacks
• Update all related tests to use the new Promise-based API

Test instructions

• yarn test:unit --spec packages/core/src/domain/session/sessionManager.spec.ts
• yarn test:unit --spec packages/logs/src/boot/preStartLogs.spec.ts
• yarn test:unit --spec packages/rum-core/src/boot/preStartRum.spec.ts

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	172.34 KiB	172.38 KiB	+34 B	+0.02%	✅
Rum Profiler	6.19 KiB	6.19 KiB	0 B	0.00%	✅
Rum Recorder	27.23 KiB	27.23 KiB	0 B	0.00%	✅
Logs	55.55 KiB	55.57 KiB	+26 B	+0.05%	✅
Rum Slim	129.83 KiB	129.84 KiB	+13 B	+0.01%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base CPU Time (ms)	Local CPU Time (ms)	𝚫%
addglobalcontext	N/A	0.0042	N/A
addaction	N/A	0.0132	N/A
adderror	N/A	0.0125	N/A
addtiming	N/A	0.0025	N/A
startview	N/A	0.0123	N/A
startstopsessionreplayrecording	N/A	0.0007	N/A
logmessage	N/A	0.0149	N/A

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
addglobalcontext	N/A	33.81 KiB	N/A
addaction	N/A	265.99 KiB	N/A
addtiming	N/A	37.01 KiB	N/A
adderror	N/A	274.96 KiB	N/A
startstopsessionreplayrecording	N/A	36.06 KiB	N/A
startview	N/A	617.30 KiB	N/A
logmessage	N/A	243.67 KiB	N/A

🔗 RealWorld

[datadog-prod-us1-6]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 81.82%
• Overall Coverage: 77.86% (+0.01%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: b5201b8 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Catch session init rejection before resolving manager

startSessionManager now awaits resolveInitialState() directly, so any rejection from strategy.setSessionState (for example storage write failures or lock acquisition failures) rejects the returned promise. The current callers in preStartLogs/preStartRum only attach .then(...), so this turns into an unhandled promise rejection and prevents SDK startup in those error paths; previously this path was guarded by monitorError instead of surfacing globally.

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[BenoitZugmeyer]

suggestion: replace ?. with !. or maybe const sessionManager = (await ...)!.

All those ?. are making tests less precise, because in cases like this:

expect(sessionManager?.findSession()!.anonymousId).toBeUndefined()

the assertion can pass when sessionManager is undefined, but it shouldn't.