Prometheus 3.8.0-rc.1

[Jan Fajerski]

We are pleased to announce that Prometheus 3.8 will soon be released,
with a number of enhancements, performance improvements and bug-fixes.

3.8 is going to be the first release with Native Histograms as a
stable feature. However, scraping Native Histograms has to be
activated explicitly via the scrape_native_histogram config setting
(newly introduced in this release).

The second release candidate adds one feature and one behavior change:

CHANGE] Remote-write 2 (receiving): Update to [.0-rc.4 spec]. "created
timestamp" (CT) is now called "start timestamp" (ST). #17411
[FEATURE] OAuth2: support jwt-bearer grant-type (RFC7523 3.1). #17592

The first release candidate already introduced a number of new
features, one change in behavior:

[CHANGE] TSDB: Native Histogram Custom Bounds with a NaN threshold are
now rejected. #17287
[FEATURE] Dockerfile: Add OpenContainers spec labels to Dockerfile. #16483
[FEATURE] SD: Add unified AWS service discovery for ec2, lightsail and
ecs services. #17046
[FEATURE] Native histograms are now a stable, but optional feature,
use the scrape_native_histogram config setting. #17232 #17315
[FEATURE] UI: Support anchored and smoothed keyword in promql editor. #17239
[FEATURE] UI: Show detailed relabeling steps for each discovered target. #17337
[FEATURE] Alerting: Add urlQueryEscape to template functions. #17403
[FEATURE] Promtool: Add Remote-Write 2.0 support to promtool push
metrics via the --protobuf_message flag. #17417

Note for users of Native Histograms
To ease the transition, the --enable-feature=native-histograms flag is
not a complete no-op in this release, but changes the default value of
scrape_native_histogram to true. In the next release (v3.9), the
feature flag will be a complete no-op, and the default value of
scrape_native_histogram will always be false. If you have been using
the feature flag so far, the recommended course of action is the
following:

Upgrade to v3.8 and keep the feature flag. Everything should work as before.
At your own pace, set scrape_native_histogram to true in all relevant
scrape configs. (There is a global and a per-scrape-config version of
scrape_native_histogram, allowing granular control if needed. It is a
good idea to also set scrape_native_histogram explicitly to false
where you do not want to scrape Native Histograms. In this way, you do
not depend on the default value of the setting anymore.)
Remove the feature flag and make sure that everything still works as intended.
Now you are ready for an upgrade to the next release (v3.9).

Changelog and binaries are available at

https://github.com/prometheus/prometheus/releases/tag/v3.8.0-rc.1

As usual, container images are available at
https://hub.docker.com/r/prom/prometheus/tags?name=v3.8.0-rc.1 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.

Jan