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Merge pull request #15854 from prometheus/beorn7/doc2

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docs: Improve documentation of promql-delayed-name-removal flag
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Julius Volz 2025-01-23 13:04:18 +01:00 committed by GitHub
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docs/feature_flags.md
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@ -131,7 +131,7 @@ Note that during this delay, the Head continues its usual operations, which incl
Despite the delay in compaction, the blocks produced are time-aligned in the same manner as they would be if the delay was not in place. Despite the delay in compaction, the blocks produced are time-aligned in the same manner as they would be if the delay was not in place.
## Delay __name__ label removal for PromQL engine ## Delay `__name__` label removal for PromQL engine
`--enable-feature=promql-delayed-name-removal` `--enable-feature=promql-delayed-name-removal`
@ -139,6 +139,18 @@ When enabled, Prometheus will change the way in which the `__name__` label is re
This allows optionally preserving the `__name__` label via the `label_replace` and `label_join` functions, and helps prevent the "vector cannot contain metrics with the same labelset" error, which can happen when applying a regex-matcher to the `__name__` label. This allows optionally preserving the `__name__` label via the `label_replace` and `label_join` functions, and helps prevent the "vector cannot contain metrics with the same labelset" error, which can happen when applying a regex-matcher to the `__name__` label.
Note that evaluating parts of the query separately will still trigger the
labelset collision. This commonly happens when analyzing intermediate results
of a query manually or with a tool like PromLens.
If a query refers to the already removed `__name__` label, its behavior may
change while this feature flag is set. (Example: `sum by (__name__)
(rate({foo="bar"}[5m]))`, see [details on
GitHub](https://github.com/prometheus/prometheus/issues/11397#issuecomment-1451998792).)
These queries are rare to occur and easy to fix. (In the above example,
removing `by (__name__)` doesn't change anything without the feature flag and
fixes the possible problem with the feature flag.)
## Auto Reload Config ## Auto Reload Config
`--enable-feature=auto-reload-config` `--enable-feature=auto-reload-config`