receive: periodic huge spikes in latency when blocks are cut #7913
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Logs from receiver during block cutting: Logs
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I found a similar discussion regarding autoscaling best practices with Thanos in a router-ingestor configuration, which might be relevant to your issue. The discussion is still open and can be found here [1]. Regarding your issue with latency spikes during block cutting, here are a few suggestions that might help:
These adjustments might help mitigate the latency spikes and improve the overall performance of your Thanos setup. |
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prometheus/prometheus#15374 should help, I think. I have been a bit busy recently so I didn't have time to dig into it 100% |
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Thanos, Prometheus and Golang version used: 0.36.1
Object Storage Provider: Azure
What happened: Recently we migrated from hard-tenancy to soft-tenancy. This means we went from having a single tenant per receive statefultset, to having around 14 tenants in one large statefulset. Since migrating, we observe huge spikes in latency on the routing receivers to the receivers:
This manifests in a large increase in 503 errors, leading to clients needing to retry requests, and a noticeable drop in throughput for a period of about 3-4 minutes:
The times in the graphs are UTC. The spikes at 07:00, 09:00, 11:00 are when blocks are cut to persistent disk. This leads to an ingestion degradation of around 5 minutes. It looks like we hit some gRPC timeouts of 5s (assumedly between routing receives and receives) and I haven't found a way to configure this or otherwise increase it.
I am not sure what happens at 08:00 and 12:00 (though the effects seem to be much smaller, note the graphs are logarithmic).
What you expected to happen: as before: no disruption to ingestion when blocks are being cut
How to reproduce it (as minimally and precisely as possible): I have only seen this issue at production loads. I will detail our setup below as best as I can.
Environment: kubernetes, AKS
Routing receives
10 replicas
4 vCPU (no limits)
16/32 GiB Memory req/lim
Receives
10 replicas
10 vCPU (no limits, no throttling)
128/256 GiB Memory req/lim
Hashring controller
We are not using Istio or any other proxy in-between routing receivers and receivers.
Full logs to relevant components: too big, will post in a separate comment.
Anything else we need to know: I can provide profiles, or anything else as needed.
Each receive has about 26 million active head series. I have tried scaling out to more, smaller, receivers (up to 60 replicas) but still saw the same issue of high latency, as well as finding that this had a negative impact on query performance.
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