Prometheus 3.14.0

Let's not get carried away with the headline features in Prometheus 3.14.0. Yes, the new Oracle Cloud discovery sounds great, and yes, durations-as-expressions are finally on by default. But this release also quietly deprecates things you are probably currently doing — and the clock is ticking on them.

The most consequential change is the deprecation of the stats query parameter on /api/v1/query and /api/v1/query_range for anything other than true and all. If you have dashboards or tooling passing values like stats=timings, they still work today, but they now emit a deprecation warning — and they will be rejected outright in the next major release. Budget some migration time now.

PromQL: What Actually Changed

The promql-duration-expr feature flag is now a no-op — duration expressions are enabled by default, so any config that was setting it can be deleted. Separately, first_over_time has been promoted to stable and no longer requires promql-experimental-functions.

• start_timestamp(instant-vector) — new experimental function returning the start timestamp of each sample; gated behind use-start-timestamps.
• rate()/increase() extrapolation — can now use start timestamps as an alternative basis for rate extrapolation, also behind the flag.
• Hetzner labels — __meta_hetzner_datacenter dropped for hcloud targets; if your relabel rules reference it, they will now produce empty values.

The Fixes Worth Knowing About

One quiet but welcome correction: /api/v1/status/config now renders separator: "" and replacement: "" in relabel configs when they are explicitly empty, instead of omitting them. Anyone debugging relabel output against this endpoint will appreciate the difference between "unset" and "explicitly empty."

The experimental support for encoding start timestamps in histograms and float histograms, hidden behind the histogram-related flag, is a peek at where the TSDB is heading — but experimental means experimental. Don't build production tooling around it yet.

The Verdict

Upgrade to 3.14.0, sure — the discovery and PromQL work is solid. Just don't ignore the deprecation warnings. The stats parameter and the Hetzner label removal are the two things most likely to bite you in a future major release, and fixing them later is always more painful than fixing them now.