Delay journey finish

[suchcodemuchwow]

This PR aims to add delay to journeys which are closing before ongoing requests to telemetry clusters finishes.

Note: We are not sure if browser buffers the event requests to server, if that is the case we have to check if buffer cleaned up. Looking for more information how analytics client sending these requests, @afharo can provide more context around that.

Fixes: #140253

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 2411bc8

Metrics [docs]

✅ unchanged

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @suchcodemuchwow

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[afharo]

Apologies for the delay in my response, just confirming that the browser side does buffer all the events for 1 second:

kibana/packages/analytics/shippers/elastic_v3/browser/src/browser_shipper.ts

Lines 106 to 107 in 9f0a9e7

	// Buffer events for 1 second or until we have an optIn value
	bufferWhen(() => interval(1000).pipe(skipWhile(() => this.isOptedIn$.value === undefined))),

There is a tear-down logic that should attempt to send all pending events. This is called in the stop lifecycle step. However, currently, core does not trigger the stop lifecycle step when closing the browser (#132696).

[spalger]

@afharo any chance we could get a global method we could call to flush the buffer, that returns a promise which resolves when the items in the buffer have been sent? It's probably not critical, but if we could call such a method from playwright then we could be very confident all telemetry produced during the test was sent without needing to worry about non-deterministic timers.

[afharo]

I'm not familiar with playwright and the scope it runs (which methods it can see and call). But happy to explore the option. We could also expose an emitter from the client or log something whenever we are done shipping all the events in the queue.

Can you create an issue so we can discuss our options?

[spalger]

Issue: #140521