ESP32 · Code review · Newbie question: how should a esp32-review config file be organised?

43
ESr/esp32-review·posted by zhu_zong·3 days agoReview

Newbie question: how should a esp32-review config file be organised?

Most esp32-review articles stop at "how to use it" and never cover "when not to use it". This is an attempt at the second half.

Worth noting: the official docs do cover this, just in a very inconspicuous spot. I only found it reading the source comments, where the author explains the reasoning — roughly "so that it degrades into predictable behaviour in extreme cases".

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.

We also fixed monitoring along the way: replaced average-based alerts with percentiles and split them per endpoint. False alerts dropped by about seventy percent and the on-call rotation visibly cheered up.

What genuinely surprised me was the tail. The average looked great while P99 jumped by an order of magnitude past some threshold. The cause was not esp32-review itself but our upstream connection reuse — the load test traffic was too clean and hid the long-tail requests.

18 comments

18 comments

M
Sslow_query·12 minutes ago

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.

493
Oops_wangMod·2 days ago

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

403
Ttang_hao·1 hour ago

This is not a esp32-review problem, it is a usage problem. The docs say this API is not thread-safe and you must lock around it yourself.

391
Lli_ming·12 minutes agoedited

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.

275
Sslow_query·2 days 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.

203
Zzhou_yi·yesterday

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

152
Sswoole_leeOP·just now

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.

9
Llinlin·3 minutes ago

Thanks for sharing real numbers — far more useful than the articles that only cover concepts.

507
Aalice_dev·28 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.

160
Mmike_xu·3 minutes ago

I just read the esp32-review source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

161
Lli_ming·28 minutes 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.

4
Wwinter·5 hours ago

One counter-example: below esp32-review 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

88
Zzhou_yi·2 days agoedited

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

1
Llinlin·2 days 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.

1
NnikicMod·just now

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

30
Ttang_hao·2 hours ago

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

507
NnikicOP·2 hours ago

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.

48
Mmike_xu·just now

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.

21

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