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CLI Tools · Career · Built a visual debugging panel for cli-tools-career over the weekend

16
CTr/cli-tools-career·posted by winter·1 hour agoTutorial

Built a visual debugging panel for cli-tools-career over the weekend

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 query that broke: a full scan over 20M rows.
-- A composite index took P99 from 1.8s down to 42ms.
SELECT id, title, created_at
  FROM posts
 WHERE community_id = ?
   AND status = 1
 ORDER BY score DESC
 LIMIT 20;

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.

What genuinely surprised me was the tail. The average looked great while P99 jumped by an order of magnitude past some threshold. The cause was not cli-tools-career itself but our upstream connection reuse — the load test traffic was too clean and hid the long-tail requests.

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.

5 comments

5 comments

M
Kkite·12 minutes 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.

215
Llinlin·3 minutes ago

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

66
Mmike_xuOP·just now

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.

138
NnikicOP·3 minutes agoedited

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

63
Hhuang_ke·just now

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

4

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