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Modding · Reading list · Hiring: remote modding-books engineer (full-time, long-term)

36
MOr/modding-books·posted by kernel_panic·1 hour agoReview

Hiring: remote modding-books engineer (full-time, long-term)

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

# Load test: do not jump straight to the max concurrency.
# Ramp it up, otherwise you miss the knee.
for c in 50 100 200 400 800; do
  wrk -t8 -c$c -d60s --latency http://127.0.0.1:8080/api/feed
  sleep 20
done

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".

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.

One last trap: in container environments remember to adjust the memory-related parameters in step. Otherwise the host limit and the process expectation disagree, and the symptom is intermittent, unreproducible failure.

19 comments

19 comments

M
Lli_mingOP·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.

364
Mmike_xu·12 minutes ago

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

410
Ddev_zhou·yesterdayedited

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.

112
Ddev_zhou·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.

212
Mmike_xu·just now

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

54
WwinterOP·1 hour ago

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

33
Sswoole_leeOP·28 minutes ago

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

308
Nnikic·2 days ago

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

121
Rrase·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.

134
Kkite·1 hour ago

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

17
Bbob_chen·3 minutes ago

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

13
Aalice_dev·1 hour 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.

466
LlinlinOP·5 hours agoedited

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.

165
Aalice_dev·28 minutes ago

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

21
Rrase·1 hour agoedited

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

149
Cchen_dev·2 days ago

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

17
Kkite·2 days ago

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

122
Kkite·1 hour 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.

7
Oops_wang·2 days 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.

6

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