July 2025 monthly summary focusing on key architectural and usability improvements in Grafana Prometheus integration. Delivered feature-level enhancement to PromQL histogram annotation handling, reducing noise and improving metric evaluation accuracy.

June 2025: Grafana Prometheus work focused on improving metric labeling clarity by adding tests for relabeling of type and unit labels. This enhances observability, dashboard reliability, and alerting accuracy by ensuring metrics are correctly labeled.

In April 2025, delivered OpenTelemetry histogram interoperability improvements for grafana/mimir, including an experimental conversion path to Prometheus native histograms (NHCB) with custom buckets, along with documentation, changelog updates, and enhanced integration tests. Also stabilized the OpenTelemetry histograms test suite by addressing flakiness, contributing to more reliable observability data and faster validation of metrics flows.

March 2025 monthly summary for grafana/prometheus focusing on feature delivery and technical progress. Key feature delivered: OTel Explicit Bucket Histogram Translation to Prometheus Native Histograms, enabling optional translation to NHCB with configurable buckets, including configuration options, tests, and documentation updates. No major bugs fixed this month for this repository. Impact: improves interoperability between OpenTelemetry histograms and Prometheus native histograms, reducing migration effort and improving data fidelity for histogram data. Technologies demonstrated: Go, OpenTelemetry integration, Prometheus histogram models, configuration management, unit/integration tests, and documentation updates. Commit of record: c90b387d898393ba000c7be5a7abda3412d4be51 with message 'Optionally translate OTel histograms to NHCB (#15850)'.

December 2024: Delivered Prometheus Histogram Enhancements in grafana/prometheus, introducing support for custom bucket histograms, expanded tests for histogram counter resets, and updated encoding benchmarks with clarifying comments. This work improves metric fidelity, performance visibility, and maintainability for histogram-based queries and alerts across users.

2024-11 Monthly summary for grafana/prometheus: Delivered foundational histogram enhancements in the Prometheus TSDB, enabling custom bucket histograms and backward-compatible encoding/decoding. This unlocks more accurate histogram-based analytics while preserving compatibility for existing workloads. Improvements in logging, tests, and documentation around histogram data handling, broader test coverage, and alignment of record types and WAL encodings to minimize breaking changes. Business impact includes improved analytics fidelity, smoother migrations for users, and reduced maintenance overhead for histogram data handling.

October 2024 monthly summary for grafana/prometheus: Delivered a focused optimization of histogram data handling, migrating away from custom value handling in the head appender and WAL toward a histogram-centric approach. Removed unused custom value buffers and related logic, and simplified histogram data structures to boost performance, reliability, and maintainability. The changes are isolated to the histogram path with clear commit history and no customer-facing feature changes.