Prometheus 2.15.0 is now out, following on from 2.14.0 with many fixes and improvements.

The big improvement in this release is that I've optimised block and compaction memory usage. Blocks no longer store all symbols/postings on the heap, and compaction no longer keeps them in memory either. The net effect is reduced memory usage for systems with high cardinality/churn, and compaction memory spikes should basically be gone now. As this is a classic RAM vs CPU tradeoff, compaction will be a bit slower. There have also been performance improvements in WAL replay (i.e. startup time), and the space taken by the WAL is now considered for size-based retention.

There's a new metric metadata endpoint, the prometheus_sd_kubernetes_cache_* metrics have been removed, and PromQL parser performance was improved a bit. Work on the React UI also continues.

There’s also a number of improvements, bug fixes and other changes, see the release notes for more detail.

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