[release-2.8.x] fix(background cache): increment queue size exactly once #11779
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**What this PR does / why we need it**: While looking at the metrics from one of our cells, we noticed that the queue size is set to a very high value even when the length is pretty much 0. Background cache is incrementing the queue size twice for each enqueued key. This pr removes the additional increment call. `TestBackgroundSizeLimit` might be flaky because of the [writeBackLoop](https://github.com/grafana/loki/blob/8eb09c78c842b61f6619fb3755a43b180536b761/pkg/storage/chunk/cache/background.go#L193) which dequeues from the channel and reduces the queue size concurrently. To make the test predictable, I have set the `WriteBackGoroutines` to 0. **Which issue(s) this PR fixes**: Fixes #<issue number> **Special notes for your reviewer**: **Checklist** - [x] Reviewed the [`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md) guide (**required**) - [ ] Documentation added - [x] Tests updated - [ ] `CHANGELOG.md` updated - [ ] If the change is worth mentioning in the release notes, add `add-to-release-notes` label - [ ] Changes that require user attention or interaction to upgrade are documented in `docs/sources/setup/upgrade/_index.md` - [ ] For Helm chart changes bump the Helm chart version in `production/helm/loki/Chart.yaml` and update `production/helm/loki/CHANGELOG.md` and `production/helm/loki/README.md`. [Example PR](d10549e) - [ ] If the change is deprecating or removing a configuration option, update the `deprecated-config.yaml` and `deleted-config.yaml` files respectively in the `tools/deprecated-config-checker` directory. [Example PR](0d4416a) (cherry picked from commit 5c8fd52)
ashwanthgoli
approved these changes
Jan 25, 2024
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Backport 5c8fd52 from #11776
What this PR does / why we need it:
While looking at the metrics from one of our cells, we noticed that the queue size is set to a very high value even when the length is pretty much 0.
Background cache is incrementing the queue size twice for each enqueued key. This pr removes the additional increment call.
TestBackgroundSizeLimitmight be flaky because of the writeBackLoop which dequeues from the channel and reduces the queue size concurrently. To make the test predictable, I have set theWriteBackGoroutinesto 0.Which issue(s) this PR fixes:
Fixes #
Special notes for your reviewer:
Checklist
CONTRIBUTING.mdguide (required)CHANGELOG.mdupdatedadd-to-release-noteslabeldocs/sources/setup/upgrade/_index.mdproduction/helm/loki/Chart.yamland updateproduction/helm/loki/CHANGELOG.mdandproduction/helm/loki/README.md. Example PRdeprecated-config.yamlanddeleted-config.yamlfiles respectively in thetools/deprecated-config-checkerdirectory. Example PR