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Open Source · Blog · open-source-blog under load on an 8-core 16GB box — full benchmark scripts included

103
OSr/open-source-blog·posted by winter·yesterdayDiscussion

open-source-blog under load on an 8-core 16GB box — full benchmark scripts included

It took me two weeks of on-and-off digging and plenty of wrong turns. Writing the process down as it happened so the next person spends less time.

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".

On trade-offs, my view is this: if nobody on the team owns this area long-term, do not introduce a second mechanism. With two coexistence you first have to work out which one is even in play when things break, and that costs far more than the performance you saved.

23 comments

23 comments

M
Kkite·2 hours agoedited

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.

475
Rrase·1 hour ago

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

417
LlinlinOP·just now

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

281
Sswoole_lee·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.

271
Hhuang_ke·28 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.

262
Hhuang_ke·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.

75
Zzhu_zong·28 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.

59
Ddev_zhou·28 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.

4
Kkite·2 hours ago

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

17
Sswoole_lee·3 minutes ago

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

1
Sswoole_lee·28 minutes ago

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

14
Aalice_devMod·2 days ago

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

328
Kkite·1 hour ago

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

13
Lli_ming·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.

220
Zzhou_yi·just now

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

217
Llinlin·12 minutes ago

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

126
Hhuang_ke·3 minutes ago

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

60
Zzhou_yi·3 minutes agoedited

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.

15
Llinlin·28 minutes ago

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

3
Ddev_zhou·12 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.

79
Zzhou_yi·5 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.

3
Rrase·2 days agoedited

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

10
Hhuang_ke·5 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.

1

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