Add optional TTL for *Vec children (MetricVec)#1986
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jpinsonneau wants to merge 2 commits intoprometheus:mainfrom
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Add optional TTL for *Vec children (MetricVec)#1986jpinsonneau wants to merge 2 commits intoprometheus:mainfrom
jpinsonneau wants to merge 2 commits intoprometheus:mainfrom
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When TTL is set on CounterOpts/GaugeOpts/HistogramOpts, Vec children that have not been accessed for longer than TTL are automatically excluded from Collect output. A CleanupExpired method is provided to explicitly remove expired entries from the internal map. This eliminates the need for external caches to track metric last-access times for expiration purposes. Made-with: Cursor Signed-off-by: Julien Pinsonneau <jpinsonn@redhat.com>
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Closing in favor of #1989 |
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Context
High-cardinality and ephemeral label sets (for example per-pod or per-connection series) are painful to manage with today’s client: the usual approach is an external shadow cache plus periodic
Delete, which duplicates label storage and repeats the same pattern across projects. This is discussed in #1983 – Proposal: built-in TTL.What this PR does
TTLfield onOpts(used byCounterVec,GaugeVec, andHistogramVec) and threads it intoMetricVecviaNewMetricVecWithTTL.lastAccessedtimestamp (Unix ms). ZeroTTLkeeps behavior identical toNewMetricVec.Collectonly emits children whose last access is within the TTL window; older children are omitted from scrape output.(*MetricVec).CleanupExpired()walks the internal map and removes expired children, returning how many were deleted. Callers that care about memory (not only hiding series from scrapes) should invoke this on a schedule they control—similar in spirit to how statsd_exporter #164 expires series at the process boundary with a periodic pass.“Access” means resolving the child through the vector API (
GetMetricWith,GetMetricWithLabelValues,With,WithLabelValues, curried variants, etc.). Holding a child handle and only callingAdd/Set/Observeon it does not refresh TTL unless the instrumentation goes through theVecagain.SummaryVecis unchanged in this PR (still usesNewMetricVecwithout TTL). CustomMetricVectypes can opt in by constructing withNewMetricVecWithTTLand exposingCleanupExpiredif desired.Tests
Adds
vec_test.gocoverage for counter/gauge/histogram TTL, partial refresh, zero TTL, andGetMetricWith.Assisted-by:
claude-4.6-opus-high