🔈 [RUM-10284] collect telemetry before starting the session manager #3602

BenoitZugmeyer · 2025-06-05T17:27:15Z

Motivation

We observed that in some condition, the SessionManager crashes. While the exception is caught and buffered in-memory for telemetry, the telemetry event itself is not sent to Datadog.

The goal of this PR is to be able to cover more ground in our telemetry monitoring and caught exceptions that are coming from the Session Manager.

Changes

Changes are kind of significative, so bare with me. As always, please review commit by commit.

The overall strategy is first to refactor Telemetry code so both Logs and RUM behave the same. This implies using a separate batch for telemetry, which was not the case for RUM.

With telemetry logic refactored, we can do some modifications that allows to send telemetry earlier, without waiting for startLogs or startRum to finish.

Test instructions

Open the sandbox in Chrome
Using chrome devtools, edit the session cookie to add &lock=1 at the end. This makes the Logs and RUM SDKs crash (specific changes for this crash will come in later PRs).
Refresh the page
Check that telemetry errors are listed in the devtools extension.
Also, check that those telemetry errors are sent to Datadog intake in the Network tab.

Checklist

Tested locally
Tested on staging
Added unit tests for this change.
Added e2e/integration tests for this change.

This is to be uniform with RUM

We don't really need to flush telemetry on session expiration. Let's break this requirement, it will allow us to start and send telemetry before starting the session manager.

This is needed to progressively set context and don't crash if context variables (ex: `session`) isn't defined yet when collecting telemetry.

codecov-commenter · 2025-06-05T17:39:52Z

Codecov Report

Attention: Patch coverage is 97.61905% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.44%. Comparing base (e5f565e) to head (7139ac7).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/core/src/domain/telemetry/telemetry.ts	96.15%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3602      +/-   ##
==========================================
+ Coverage   92.37%   92.44%   +0.07%     
==========================================
  Files         323      322       -1     
  Lines        8132     8129       -3     
  Branches     1842     1840       -2     
==========================================
+ Hits         7512     7515       +3     
+ Misses        620      614       -6

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cit-pr-commenter · 2025-06-05T17:46:50Z

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	146.83 KiB	147.40 KiB	585 B	+0.39%	✅
Rum Recorder	18.02 KiB	18.02 KiB	0 B	0.00%	✅
Rum Profiler	4.63 KiB	4.63 KiB	0 B	0.00%	✅
Logs	51.70 KiB	51.91 KiB	210 B	+0.40%	✅
Flagging	0 B	935 B	935 B	N/A%	✅
Rum Slim	106.45 KiB	106.96 KiB	524 B	+0.48%	✅
Worker	23.59 KiB	23.59 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.015	0.013	-0.002
addaction	0.039	0.041	0.002
addtiming	0.010	0.009	-0.001
adderror	0.038	0.038	-0.000
startstopsessionreplayrecording	0.002	0.002	0.000
startview	0.010	0.010	-0.000
logmessage	0.047	0.042	-0.004

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	26.61 KiB	26.96 KiB	366 B
addaction	51.16 KiB	54.76 KiB	3.60 KiB
addtiming	26.09 KiB	25.95 KiB	-135 B
adderror	58.89 KiB	59.04 KiB	147 B
startstopsessionreplayrecording	23.99 KiB	24.92 KiB	955 B
startview	428.01 KiB	432.01 KiB	4.01 KiB
logmessage	57.78 KiB	60.00 KiB	2.22 KiB

🔗 RealWorld

amortemousque · 2025-06-06T07:58:42Z

packages/core/src/domain/telemetry/telemetry.ts

@@ -45,8 +50,8 @@ export const enum TelemetryService {
 }

 export interface Telemetry {
-  setContextProvider: (provider: () => Context) => void
-  observable: Observable<TelemetryEvent & Context>
+  setContextProvider: (key: string, contextProvider: () => ContextValue | undefined) => void


💭 thought: ‏Using a new hook like assembleTelemetry you could get rid of this setContextProvider(No need to do it right now but just to keep in mind)

packages/rum-core/src/domain/startCustomerDataTelemetry.spec.ts

…ry-batch

bcaudan

Very nice!

bcaudan · 2025-06-06T13:52:39Z

packages/core/src/domain/telemetry/telemetry.spec.ts

-      telemetry.setContextProvider(() => ({
-        foo: 'bar',
-      }))
+      telemetry.setContextProvider('foo', () => 'bar')


💬 suggestion: what about adding a test to illustrate "the progressively set context" case?‏

BenoitZugmeyer · 2025-06-11T07:16:05Z

/merge

dd-devflow · 2025-06-11T07:16:08Z

View all feedbacks in Devflow UI.

2025-06-11 07:16:08 UTC ℹ️ Start processing command /merge

2025-06-11 07:16:12 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 27m (p90).

2025-06-11 07:36:58 UTC ℹ️ MergeQueue: This merge request was merged

BenoitZugmeyer added 10 commits June 5, 2025 17:40

✅ use fake telemetry in customerDataTelemetry

b78819c

✅ use fake telemetry in rumInternalContext

8772e61

🚚 add logs telemetry configuration in preStartLogs

21705d4

This is to be uniform with RUM

🚚 move Logs telemetry transport logic to core

1b834e1

🔥 do not rely on session manager to flush telemetry

ba7a8f3

We don't really need to flush telemetry on session expiration. Let's break this requirement, it will allow us to start and send telemetry before starting the session manager.

♻️ allow setting telemetry context property by property

89078a6

This is needed to progressively set context and don't crash if context variables (ex: `session`) isn't defined yet when collecting telemetry.

♻️ allow passing a createEncoder to telemetry transport

205f3c6

🚚 start transport and drain in startTelemetry

ef3681c

✅ adjust e2e test as telemetry is sent separately

dea7c9f

🚚 start logs telemetry before session manager

54b02ba

BenoitZugmeyer force-pushed the benoit/common-telemetry-batch branch from 5b7bde8 to 54b02ba Compare June 5, 2025 17:37

amortemousque reviewed Jun 6, 2025

View reviewed changes

BenoitZugmeyer changed the title ~~🔈 collect telemetry before starting the session manager~~ 🔈 [RUM-10284] collect telemetry before starting the session manager Jun 6, 2025

👌 fix typo

d8c4552

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dd-devflow bot added a commit that referenced this pull request Jun 6, 2025

[skip ci] #3602 conflicts with staging-23

01322f8

dd-devflow bot mentioned this pull request Jun 6, 2025

[fixme] #3602 conflicts with staging-23 #3605

Closed

Merge remote-tracking branch 'origin/main' into benoit/common-telemet…

308806e

…ry-batch

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dd-devflow bot added the staging-23 label Jun 6, 2025

BenoitZugmeyer force-pushed the benoit/common-telemetry-batch branch 2 times, most recently from c0ec56e to 6f805b9 Compare June 6, 2025 12:53

✅ add an e2e test

6c68f88

BenoitZugmeyer force-pushed the benoit/common-telemetry-batch branch from 6f805b9 to 6c68f88 Compare June 6, 2025 13:04

BenoitZugmeyer marked this pull request as ready for review June 6, 2025 13:33

BenoitZugmeyer requested a review from a team as a code owner June 6, 2025 13:33

bcaudan approved these changes Jun 6, 2025

View reviewed changes

👌 add a unit test for progressive telemetry context

7139ac7

amortemousque approved these changes Jun 11, 2025

View reviewed changes

dd-devflow bot added mergequeue-status: queued mergequeue-status: in_progress and removed mergequeue-status: queued labels Jun 11, 2025

dd-mergequeue bot merged commit 41d37d6 into main Jun 11, 2025
20 checks passed

dd-mergequeue bot deleted the benoit/common-telemetry-batch branch June 11, 2025 07:36

dd-devflow bot added mergequeue-status: done and removed mergequeue-status: in_progress labels Jun 11, 2025

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Motivation

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Test instructions

Checklist

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