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tmux · Advanced · Ten tmux-pro anti-patterns — how many are you guilty of?

65
TMr/tmux-pro·posted by rase·2 hours agoHelp

Ten tmux-pro anti-patterns — how many are you guilty of?

Short version: tmux-pro needs almost no tuning at small and medium scale — the point where it starts to hurt is much further out than most people assume. Full measurements below.

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.

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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27 comments

27 comments

M
Lli_ming·2 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.

507
Kkernel_panic·2 days ago

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

258
Rran_bo·2 days ago

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

380
Zzhou_yiOP·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.

254
Ttang_haoOP·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.

269
Rran_bo·12 minutes ago

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

320
Bbob_chen·yesterday

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.

94
Lli_mingMod·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.

55
Ttang_hao·3 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.

23
Sswoole_lee·5 hours ago

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

297
Kkite·1 hour ago

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

279
Aalice_dev·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.

212
Hhuang_ke·3 minutes ago

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

210
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.

185
Rran_bo·3 minutes 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.

247
Wwinter·3 minutes ago

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

118
KkiteOP·just now

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

6
Oops_wang·28 minutes agoedited

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

199
Kkernel_panicOPMod·2 days ago

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

80
Cchen_devOPMod·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.

102
Hhuang_ke·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.

2
Oops_wang·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.

78
Ttang_hao·28 minutes ago

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

66
Rran_bo·2 days ago

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

437
Rrase·3 minutes ago

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

34
Zzhu_zong·just nowedited

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.

26
Sslow_query·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.

27

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