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Rust Community · Two weeks with Rust: what feels right and what drives me up the wall

14
Rsr/rust·posted by rase·2 hours agoPostmortem

Two weeks with Rust: what feels right and what drives me up the wall

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

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 Rust itself but our upstream connection reuse — the load test traffic was too clean and hid the long-tail requests.

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7 comments

7 comments

M
Kkernel_panic·2 hours agoedited

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

230
Rran_boOP·3 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.

2
Ttang_hao·3 minutes agoedited

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

10
Cchen_dev·just nowedited

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.

233
Zzhou_yi·12 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.

278
Sslow_query·28 minutes 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.

103
Llinlin·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.

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