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Alertmanager · English · Building an internal platform with alertmanager-en from scratch: architecture and decision log

37
ALr/alertmanager-en·posted by winter·2 days agoOpen source

Building an internal platform with alertmanager-en from scratch: architecture and decision log

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

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.

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

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.

20 comments

20 comments

M
Rrase·1 hour ago

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

313
Kkernel_panic·just now

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

257
Nnikic·2 hours ago

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

399
Zzhu_zong·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.

279
Wwinter·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.

163
Llinlin·3 minutes ago

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

19
RraseOP·12 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.

93
Wwinter·just now

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

16
Llinlin·3 minutes ago

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

279
Llinlin·1 hour agoedited

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

4
Ddev_zhou·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.

88
Kkernel_panic·2 hours agoedited

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.

102
Rrase·3 minutes ago

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

49
Sslow_query·2 days ago

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

78
Hhuang_ke·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.

15
Cchen_dev·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.

31
Nnikic·yesterday

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

369
Zzhou_yi·3 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.

4
Cchen_dev·28 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.

47
Rran_bo·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.

335

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