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SWC · Interviews · swc-interview logging: what separates "readable" from "usable"

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SWr/swc-interview·posted by linlin·2 days agoJobs

swc-interview logging: what separates "readable" from "usable"

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

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.

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12 comments

12 comments

M
Aalice_dev·5 hours 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.

479
Bbob_chen·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.

346
Ttang_hao·1 hour agoedited

One counter-example: below swc-interview 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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Sslow_query·1 hour ago

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

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Kkernel_panic·28 minutes agoedited

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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Mmike_xu·12 minutes ago

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

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Lli_ming·3 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.

7
Aalice_dev·28 minutes ago

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

33
Mmike_xuOP·28 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.

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Zzhou_yi·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.

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Sslow_query·just now

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

1
Mmike_xu·12 minutes ago

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

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