Here is a list of features that are disabled by default since they are breaking changes or are considered experimental. Their behaviour can change in future releases which will be communicated via the release changelog.
You can enable them using the
--enable-feature flag with a comma separated list of features.
They may be enabled by default in future versions.
@ modifier lets you specify the evaluation time for instant vector selectors,
range vector selectors, and subqueries. More details can be found here.
$var in the
values according to the values of the current environment variables. References
to undefined variables are replaced by the empty string.
This negative offset is disabled by default since it breaks the invariant that PromQL does not look ahead of the evaluation time for samples.
In contrast to the positive offset modifier, the negative offset modifier lets one shift a vector selector into the future. An example in which one may want to use a negative offset is reviewing past data and making temporal comparisons with more recent data.
More details can be found here.
The remote write receiver allows Prometheus to accept remote write requests from other Prometheus servers. More details can be found here.
OpenMetrics introduces the ability for scrape targets to add exemplars to certain metrics. Exemplars are references to data outside of the MetricSet. A common use case are IDs of program traces.
Exemplar storage is implemented as a fixed size circular buffer that stores exemplars in memory for all series. Enabling this feature will enable the storage of exemplars scraped by Prometheus. The flag
storage.exemplars.exemplars-limit can be used to control the size of circular buffer by # of exemplars. An exemplar with just a
traceID=<jaeger-trace-id> uses roughly 100 bytes of memory via the in-memory exemplar storage. If the exemplar storage is enabled, we will also append the exemplars to WAL for local persistence (for WAL duration).
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