Prometheus 3.9.0-rc.0

[Bryan Boreham]

We are pleased to announce that Prometheus 3.9 will be released soon, most likely after the holiday season, with a number of enhancements, performance improvements and bug-fixes. A Release Candidate is now available for you to test.

In version 3.9, Native Histograms is no longer experimental, and the feature flag native-histogram has no effect.  You must now turn on 

the config setting scrape_native_histogram to collect Native Histogram samples from exporters.

The other change in behaviour and new features are:

- [CHANGE] API: Add maximum limit of 10,000 sets of statistics to TSDB status endpoint. #17647

- [FEATURE] API: Add /api/v1/features for clients to understand which features are supported. #17427

- [FEATURE] Promtool: Add `start_timestamp` field for unit tests. #17636

- [FEATURE] Promtool: Add `--format seriesjson` option to `tsdb dump` to output just series labels in JSON format. #13409

- [FEATURE] Add `--storage.tsdb.delay-compact-file.path` flag for better interoperability with Thanos. #17435

- [FEATURE] UI: Add an option on the query drop-down menu to duplicate that query panel. #17714

Changelog and binaries are available at

https://github.com/prometheus/prometheus/releases/tag/v3.9.0-rc.0

As usual, container images are available at
https://hub.docker.com/r/prom/prometheus/tags?name=v3.9.0-rc.0 and
https://quay.io/repository/prometheus/prometheus?tab=tags.

Please try out the release candidate on a non-critical environment and
let us know what you find.