*: improve latency when streaming series from Prometheus #3146
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I've found that when requesting many series (in the order of ten thousands), the Thanos sidecar spends half of its time computing the number of received series. To calculate the number of series, it needs to build a label-based identifier for each chunked series and compare it with the previous identifier. Eventually this number is only used for logging and tracing so it doesn't feel like it's worth the penalty. This change adds an histogram metric, `thanos_sidecar_prometheus_store_received_frames`, which tracks the number of frames per request received from the Prometheus remote read API (buckets: 10, 100, 1000, 10000, 100000). It can be used to evaluate whether expensive Series requests are being performed. Signed-off-by: Simon Pasquier <spasquie@redhat.com>
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@bwplotka friendly ping :) |
bwplotka
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Sep 15, 2020
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Thanks, amazingly spotted ❤️ |
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Changes
I've found that when requesting many series (in the order of ten
thousands), the Thanos sidecar spends half of its time computing the
number of received series. To calculate the number of series, it needs
to build a label-based identifier for each chunked series and compare it
with the previous identifier. Eventually this number is only used for
logging and tracing so it doesn't feel like it's worth the penalty.
This change adds an histogram metric,
thanos_sidecar_prometheus_store_received_frames, which tracks the numberof frames per request received from the Prometheus remote read API
(buckets: 10, 100, 1000, 10000, 100000). It can be used to evaluate
whether expensive Series requests are performed.
Verification
CPU profile before this PR (half of the time is spent in
prompb.(*Label).String)CPU profile after this PR
CPU graph showing the 50% improvement (the patched version of the Thanos sidecar has been deployed around 15:50)
https://snapshot.raintank.io/dashboard/snapshot/mufpH3k2yRJUYLM284SXESwVLG0Ns14i?orgId=2