[kernel 1116] browser logging: cdp pipeline by archandatta · Pull Request #194 · kernel/kernel-images

archandatta · 2026-04-01T13:26:28Z

Scaffolding of the CDP Pipeline implementation on the functions are in -> #202

Note

Medium Risk
Introduces new capture-session lifecycle endpoints and wiring that affects API startup/shutdown and event persistence; while mostly scaffolding, it adds concurrency/lifecycle management and new disk writes that could misbehave under load or during shutdown.

Overview
Adds a new capture session resource backed by an events pipeline and CDP monitor scaffold, including POST/GET/PATCH/DELETE /events/capture_session to start, inspect, reconfigure (category filtering), and stop capture.

Wires the API service to own a long-lived events.CaptureSession and cdpmonitor.Monitor, constructs them in main, and ensures they are stopped/closed during ApiService.Shutdown.

Refactors the events package to support reusable sessions (Start/Stop), category validation/filtering, ring buffer reset, and safer file writing (create log dir, filename-based writes), and updates generated oapi types/clients plus new unit tests for the capture session handlers.

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server/cmd/api/api/api.go

server/cmd/api/api/events.go

server/lib/events/event.go

…ies and fix delimiter in CategoryFor

server/cmd/api/api/events.go

server/lib/events/ringbuffer.go

hiroTamada · 2026-04-07T13:45:54Z

server/cmd/api/api/api.go

 }

 func (s *ApiService) Shutdown(ctx context.Context) error {
+	s.monitorMu.Lock()


Is this going to add a latency in delete browsers request? If so, how much?

Shouldn't add any latency, shutdown holds the lock briefly to stop the CDP monitor and close the capture session i think both are fast synchronous teardown calls

server/cmd/api/main.go

rgarcia · 2026-04-07T15:09:28Z

server/cmd/api/api/events.go

+
+	s.captureSession.Start(uuid.New().String())
+
+	if err := s.cdpMonitor.Start(context.Background()); err != nil {


the comment says this restarts an existing monitor, but the handler never checks/stops an already-running one. might be worth making that behavior explicit here instead of relying on Start() side effects.

Ah yeah this was just a scaffolding I did for the actual implementation. I should've mentioned that there is a chained PR #202 that is capturing this https://github.com/kernel/kernel-images/pull/202/changes#diff-0ddb00e75e5f21a1deb16fb852c7f352f234bbf0b9ddcc3d11639b1d3293c572R90

rgarcia · 2026-04-07T15:09:28Z

server/cmd/api/api/events.go

+// Generates a new capture session ID, seeds the pipeline, then starts the
+// CDP monitor. If already running, the monitor is stopped and
+// restarted with a fresh session ID
+func (s *ApiService) StartCapture(w http.ResponseWriter, r *http.Request) {


question: is a no-arg /events/start intentional? i'd expect callers to want some capture config here over time (categories, detail level, screenshot/network verbosity, etc.), or at least an explicit note that this is a fixed server-defined profile for now.

yeah good point, added a body field to be able to send something like

{ "categories": ["console", "network"], "detailLevel": "verbose" }

server/cmd/api/main.go

rgarcia · 2026-04-07T15:09:28Z

server/lib/cdpmonitor/monitor.go

+}
+
+// New creates a Monitor. displayNum is the X display for ffmpeg screenshots.
+func New(_ UpstreamProvider, _ PublishFunc, _ int) *Monitor {


i don't think we'll need displayNum for a pure CDP monitor, so i'd remove this until actual implementation lands.

this is handled in #202

server/lib/events/capturesession.go

server/lib/events/event.go

…structor

… and category validation

server/lib/oapi/oapi.go

server/cmd/api/api/api.go

server/cmd/api/api/events.go

…ffer clear

…alloc in filewriter, fix session doc

server/openapi.yaml

server/lib/events/capturesession.go

rgarcia

api binary needs to be removed

server/lib/events/filewriter.go

server/lib/events/ringbuffer.go

server/openapi.yaml

server/lib/events/event.go

This binary is tracked on main and was incidentally deleted earlier on this branch. Restoring it keeps the 13.4MB binary out of this PR's diff. Removing the tracked binary from main should be done in a separate PR.

server/lib/cdpmonitor/monitor.go

server/cmd/api/api/api.go

server/cmd/api/main.go

rgarcia

one small thing but otherwise i think this is good to go!

rgarcia · 2026-04-09T19:20:09Z

server/cmd/api/api/capture_session.go

+		return oapi.StartCaptureSession400JSONResponse{BadRequestErrorJSONResponse: oapi.BadRequestErrorJSONResponse{Message: err.Error()}}, nil
+	}
+
+	id := uuid.New().String()


let's use github.com/nrednav/cuid2 to be consistent with the rest of the api (and remove format: uuid for this id field in the openapi.yaml spec)

Sayan-

I think the last bugbot comment is worth resolving. Thanks for iterating - interfaces, components, and integration are looking great!

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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server/cmd/api/api/capture_session.go

archandatta commented Apr 2, 2026

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archandatta marked this pull request as ready for review April 2, 2026 15:19

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Base automatically changed from archand/kernel-1116/browser-logging to main April 2, 2026 15:34

archandatta force-pushed the archand/kernel-1116/cdp-pipeline branch from 1e544a7 to 6d929c8 Compare April 2, 2026 17:39

feat: add CDP pipeline, cdpmonitor, and wire into API service

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archandatta force-pushed the archand/kernel-1116/cdp-pipeline branch from 6d929c8 to 76d837f Compare April 2, 2026 17:44

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archandatta added 2 commits April 2, 2026 18:23

refactor: rename Pipeline to CaptureSession and delete pipeline.go

5c0f7ae

review: fix request context leak in StartCapture, add missing categor…

ad2dd63

…ies and fix delimiter in CategoryFor

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review: clean up syntax

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archandatta requested review from Sayan-, hiroTamada and rgarcia April 6, 2026 12:43

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archandatta added 5 commits April 7, 2026 18:00

review: move CategoryFor to cdpmonitor package

d086571

review: internalize ring buffer and file writer in CaptureSession con…

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…structor

review: write logs under /var/log/kernel and ensure dir exists

64e67b1

review: add capture config to /events/start and OpenAPI spec

048f9c6

review: fix lifecycle context, stop-before-reset ordering, seq reset,…

e57e58a

… and category validation

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archandatta added 2 commits April 7, 2026 18:39

fix: oapi version

886b893

fix: Shutdown cancels context outside lock, racing with StartCapture

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archandatta requested review from hiroTamada and rgarcia April 7, 2026 18:42

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review: validate DetailLevel with generated Valid

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archandatta added 3 commits April 7, 2026 19:22

review: guard zero-capacity ring buffer and fix reader reset after bu…

3523994

…ffer clear

review: use t.TempDir in test helper, map-based ValidCategory, avoid …

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…alloc in filewriter, fix session doc

review: add captureConfigFrom and StartCapture/StopCapture handler tests

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archandatta mentioned this pull request Apr 8, 2026

[kernel-1116] browser debug: add cdp monitor #202

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feat: refactor events API to resource-style capture sessions

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archandatta added 6 commits April 9, 2026 15:03

review: update file writer to be internal to the package

c6dd362

review: tighten to Write(filename string, data []byte) error

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review: update panic -> error

a8bdeaf

review: update oapi and remove detail level

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review: remove url

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chore: restore server/api on branch

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This binary is tracked on main and was incidentally deleted earlier on this branch. Restoring it keeps the 13.4MB binary out of this PR's diff. Removing the tracked binary from main should be done in a separate PR.

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archandatta added 3 commits April 9, 2026 17:07

review: harden captureConfigFromOAPI and clarify stop comment

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Sayan- approved these changes Apr 9, 2026

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review: update uuid to cuid2

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archandatta added 3 commits April 10, 2026 15:22

Merge branch 'main' into archand/kernel-1116/cdp-pipeline

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Merge branch 'main' into archand/kernel-1116/cdp-pipeline

3da65c3

fix naming

a7b2e54


		s.captureSession.Start(uuid.New().String())

		if err := s.cdpMonitor.Start(context.Background()); err != nil {

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