feat(replay): Use requestIdleCallback for events

[mydea]

This PR updates the event handling of replay to use window.requestIdleCallback, if available.
This API is supported everywhere except for Safari, and should schedule a callback to be run when the browser has "resources" for it.

Hopefully, this should improve performance in scenarios where a lot of events are emitted.

I defined a max. timeout of 50ms, meaning that after max. 50ms each callback will be executed anyhow. This could be tweaked, but feels like a reasonably defensive value here. If the API is not available, we just run the callbacks immediately (like now), so it should degrade gracefully.

Note that there would also be an approach to only have a single callback that keeps an internal queue, but that would require more work to ensure that events cannot be postponed for too long, so IMHO this is the easier solution.

I tried this in my super simple test app, where it works as expected. it would be nice though to test this in a more complex app...

Note: I also refactored the addUpdate method to split this into dedicated methods, as this was a bit mixed up right now. Now, we have a dedicated (private) method for the event emitting, and one for adding a "generic" event from other handlers etc.

See https://w3c.github.io/requestidlecallback/ for some more info.

ref #6946
ref #7085

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.09 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	62.23 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.71 KB (0%)
@sentry/browser - ES6 CDN Bundle (minified)	55.37 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	20.44 KB (0%)
@sentry/browser - Webpack (minified)	66.81 KB (0%)
@sentry/react - Webpack (gzipped + minified)	20.47 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.9 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	27.03 KB (+0.01% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.29 KB (0%)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	42.57 KB (+0.13% 🔺)
@sentry/replay - Webpack (gzipped + minified)	36.78 KB (+0.16% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	60.29 KB (+0.09% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	53.83 KB (+0.11% 🔺)

[github-actions]

Replay SDK metrics 🚀

		Plain	+Sentry			+Replay
	Revision	Value	Value	Diff	Ratio	Value	Diff	Ratio
LCP	This PR b458a65	109.01 ms	136.56 ms	+27.55 ms	+25.27 %	176.50 ms	+67.49 ms	+61.91 %
	Baseline 4c07d02	95.26 ms	129.60 ms	+34.34 ms	+36.05 %	163.27 ms	+68.01 ms	+71.39 %
CLS	This PR b458a65	0.06 ms	0.06 ms	+0.00 ms	+0.01 %	0.06 ms	+0.00 ms	+0.14 %
	Baseline 4c07d02	0.06 ms	0.06 ms	+0.00 ms	+0.00 %	0.06 ms	+0.00 ms	+0.05 %
CPU	This PR b458a65	23.32 %	24.07 %	+0.75 pp	+3.20 %	33.59 %	+10.27 pp	+44.05 %
	Baseline 4c07d02	22.20 %	22.83 %	+0.62 pp	+2.80 %	29.77 %	+7.57 pp	+34.09 %
JS heap avg	This PR b458a65	1.94 MB	2 MB	+56.85 kB	+2.93 %	2.87 MB	+927.53 kB	+47.83 %
	Baseline 4c07d02	1.93 MB	1.99 MB	+59.82 kB	+3.09 %	2.85 MB	+918.59 kB	+47.51 %
JS heap max	This PR b458a65	2.32 MB	2.56 MB	+236.76 kB	+10.20 %	3.36 MB	+1.04 MB	+44.72 %
	Baseline 4c07d02	2.31 MB	2.56 MB	+242.26 kB	+10.47 %	3.35 MB	+1.03 MB	+44.66 %
netTx	This PR b458a65	0 B	0 B	0 B	n/a	2.4 kB	+2.4 kB	n/a
	Baseline 4c07d02	0 B	0 B	0 B	n/a	2.22 kB	+2.22 kB	n/a
netRx	This PR b458a65	0 B	0 B	0 B	n/a	41 B	+41 B	n/a
	Baseline 4c07d02	0 B	0 B	0 B	n/a	41 B	+41 B	n/a
netCount	This PR b458a65	0	0	0	n/a	1	+1	n/a
	Baseline 4c07d02	0	0	0	n/a	1	+1	n/a
netTime	This PR b458a65	0.00 ms	0.00 ms	0.00 ms	n/a	109.82 ms	+109.82 ms	n/a
	Baseline 4c07d02	0.00 ms	0.00 ms	0.00 ms	n/a	127.76 ms	+127.76 ms	n/a

Baseline results on branch: develop

Revision	LCP	CLS	CPU	JS heap avg	JS heap max	netTx	netRx	netCount	netTime
1c9ed4f	+50.07 ms	-0.00 ms	+6.39 pp	+928.84 kB	+1.05 MB	+2.2 kB	+41 B	+1	+70.97 ms
1921888	+55.79 ms	+0.00 ms	+5.50 pp	+926.71 kB	+1.06 MB	+2.23 kB	+41 B	+1	+79.78 ms
e9eec27	+61.38 ms	-0.00 ms	+6.04 pp	+927.84 kB	+1.05 MB	+2.21 kB	+41 B	+1	+88.58 ms
d604022	+58.83 ms	-0.00 ms	+7.65 pp	+930.16 kB	+1.05 MB	+2.21 kB	+41 B	+1	+109.63 ms
a961e57	+54.75 ms	-0.00 ms	+6.50 pp	+929.18 kB	+1.07 MB	+2.21 kB	+41 B	+1	+92.73 ms
f7c0a2f	+46.14 ms	+0.00 ms	+6.37 pp	+921.47 kB	+1.06 MB	+2.23 kB	+41 B	+1	+207.30 ms
cb19818	+57.16 ms	+0.00 ms	+11.95 pp	+1.07 MB	+2.21 MB	+2.52 kB	+41 B	+1	+111.50 ms
ee301c3	+71.07 ms	-0.00 ms	+12.64 pp	+1.07 MB	+2.22 MB	+2.55 kB	+41 B	+1	+94.67 ms
93c4759	+61.10 ms	-0.00 ms	+12.72 pp	+1.08 MB	+2.19 MB	+2.57 kB	+41 B	+1	+116.75 ms

---

*) pp - percentage points - an absolute difference between two percentages.
Last updated: Wed, 15 Feb 2023 11:25:05 GMT

[billyvg]

Let's hold off on this change for now unless we can show some measureable improvements

[mydea]

Let's hold off on this change for now unless we can show some measureable improvements

Yes, definitely!

[mydea]

Closing this for now, as we're going to explore a different approach - see getsentry/rrweb#58