divviup / divviup/janus

Expose a custom metric for Aggregator autoscaling decisions

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Dominant language
Rust
Stars
70
Forks
16
Avg merge
4h 36m
Merged PRs (30d)
30

Description

[...] I wonder if we could use request-queue length as one of the signals to drive scaling decisions.

Originally posted by @branlwyd in https://github.com/divviup/janus/issues/3369#issuecomment-2332598983

It's worth pulling this out, as CPU usage also spikes in the aggregator during the aggregate share (reduce) phase -- and can lead to autoscaling up during single-threaded operation fruitlessly.

When we have a suitable custom metric available, we can expose it and use it for autoscaling decsisions.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
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Research direction

No files, tests, or entry points are named. Start by locating the Aggregator's request-queue handling and existing metric exposure, then trace how a custom metric can support autoscaling decisions; done means a suitable Aggregator signal is exposed for that use.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
cloud, devops, observability
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
40/100

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