Verilog · Beginners · Two weeks with verilog-newbie: what feels right and what drives me up the wall

180
VEr/verilog-newbie·posted by li_ming·1 hour agoDiscussion

Two weeks with verilog-newbie: what feels right and what drives me up the wall

Some background first. Our setup is verilog-newbie plus three downstream services, seven figures of daily requests, peaking around nine in the evening.

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.

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".

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42 comments

42 comments

M
Lli_ming·12 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.

506
Aalice_dev·2 days ago

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

435
Kkite·just nowedited

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

365
Llinlin·just now

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

17
Bbob_chen·3 minutes ago

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

2
Oops_wang·2 days 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.

171
Ddev_zhou·2 hours ago

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

23
Lli_ming·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.

96
Rran_bo·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.

344
Hhuang_ke·5 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.

331
Hhuang_ke·12 minutes ago

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

48
Rran_bo·yesterday

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

7
Rran_bo·2 days ago

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

466
Nnikic·1 hour 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.

442
Nnikic·3 minutes ago

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

9
Sswoole_lee·2 days 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.

155
Kkernel_panic·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.

266
Ttang_hao·28 minutes ago

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

281
Cchen_dev·3 minutes 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.

292
Sslow_queryOP·2 days ago

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.

178
Wwinter·2 hours ago

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

185
Wwinter·2 days 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.

39
Sswoole_lee·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.

504
Zzhou_yiMod·2 hours 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.

429
Sslow_query·2 hours ago

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

165
Ddev_zhou·2 hours ago

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

430
Sswoole_leeOP·28 minutes ago

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

204
Aalice_dev·2 days ago

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

134
Kkernel_panic·2 days ago

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

415
Aalice_dev·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.

100
Rran_bo·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.

70
Sslow_query·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.

497
Bbob_chenOP·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.

10
Ddev_zhouOP·5 hours ago

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.

1
Zzhou_yi·yesterday

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.

54
Hhuang_ke·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.

54
Sslow_query·just now

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

42
Rran_bo·12 minutes ago

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

98
Rrase·2 days ago

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

20
Ddev_zhou·1 hour 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.

13
Kkernel_panic·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.

2
Nnikic·2 days ago

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

2

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