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Baking · Events · Two weeks with baking-events: what feels right and what drives me up the wall

27
BAr/baking-events·posted by ops_wang·5 minutes agoAnnouncement

Two weeks with baking-events: what feels right and what drives me up the wall

Most baking-events articles stop at "how to use it" and never cover "when not to use it". This is an attempt at the second half.

The first thing was to collapse the variables. We were changing config and upgrading the version at the same time, and afterwards nobody could say which change caused what. We rolled back to moving one variable at a time, re-ran three times, and only then did the curve settle. Tedious, but not skippable.

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13 comments

13 comments

M
Zzhou_yi·12 minutes ago

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

344
Ttang_hao·3 minutes ago

Sharing our numbers, 8 cores 16GB, same scenario:

| Concurrency | P50 | P99 |
|---|---|---|
| 200 | 12ms | 88ms |
| 500 | 31ms | 340ms |

P99 clearly collapses at 500 concurrency, which lines up with your knee point.

10
Hhuang_ke·1 hour ago

A question: what changes in a container with a 512Mi memory limit? That is how we run it in production.

389
Nnikic·2 days agoedited

One counter-example: below baking-events 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

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Zzhou_yi·3 minutes ago

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

231
Hhuang_ke·just now

We have run this in production for two years without hitting it. That said, we never reached this scale, so our experience is not really evidence here.

162
Ddev_zhou·3 minutes ago

Agreeing with the above. One addition: with this option enabled the GC count in your metrics doubles, so adjust the alert threshold at the same time or it will keep firing.

417
Kkite·2 hours ago

This matches what we see in production. We only hit it past 3k QPS; the earlier load tests showed nothing — the test traffic was too clean, with no long-tail requests.

209
Ddev_zhou·just now

I see point 3 differently. The trade-off depends on your read/write ratio: read-heavy with little writing means caching actually widens the inconsistency window.

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Mmike_xuOP·2 hours ago

There is actually a simpler fix that needs no architecture change: move this check up to the gateway and the problem disappears. The cost is one extra lookup at the gateway.

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Zzhou_yiOP·just now

Can you give a minimal reproduction? I ran it locally for ten minutes and could not reproduce on macOS with the latest version.

5
Rran_bo·2 days ago

I just read the baking-events source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

1
KkiteMod·2 hours ago

Saved. I am reworking this area this week — this saves a lot of wrong turns.

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