Prometheus labels API: add rest action#144952
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felixbarny merged 8 commits intoelastic:mainfrom Mar 31, 2026
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Per Prometheus API semantics, omitting the limit parameter means no limit (equivalent to limit=0). Change DEFAULT_LIMIT from 10_000 to 0 so that clients which do not pass limit receive all matching label names. The plan builder (in the parent branch) already handles limit=0 by emitting an explicit Limit(Integer.MAX_VALUE) node, avoiding the AddImplicitLimit rule's silent 1 000-row cap.
Expand the terse "0 means unlimited" comment to explain the full sentinel semantics: limit=0 defers to ESQL result_truncation_max_size, limit>0 uses limit+1 as a sentinel for truncation detection.
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Pinging @elastic/es-storage-engine (Team:StorageEngine) |
kkrik-es
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Mar 30, 2026
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| List<String> data = queryLabelsData("labels_round_trip_gauge"); | ||
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| assertThat(data, hasItem("__name__")); |
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Check also returned values per item?
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The labels API only returns the label names. There's another PR to add the label values API, which returns all values for a particular label.
kkrik-es
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Mar 30, 2026
Replace partial hasItem checks with containsInAnyOrder to verify the complete set of returned labels, catching unexpected additions. Also remove erroneous FeatureFlag.PROMETHEUS_FEATURE_FLAG reference that does not exist in the FeatureFlag enum.
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…rics * upstream/main: (428 commits) ESQL: DS: Add inference/RERANK tests (elastic#145229) Unmute MMR logical plan test (elastic#145311) Do not attempt marking store as corrupted if the check is rejected due to shutdown (elastic#145209) feat(tsdb): add pipeline runtime and rename stage interfaces (elastic#145175) Fix UnresolvedException on PromQL by(step) grouping (elastic#145307) ES|QL: Optimize MMR by reducing cache size and lookup (elastic#145014) Prometheus labels/series APIs: support multiple match[] selectors (elastic#145298) Move ClientScrollablePaginatedHitSource into Reindex Module (elastic#144100) mute test class for elastic#145277 CPS mode for ViewResolver (elastic#145219) [ESQL] Disables GroupedTopNBenchmark temporarily (elastic#145124) Make exponential_histogram the default histogram type for HTTP OTLP endpoint (elastic#145065) More tests requiring an explicit confidence interval (elastic#145232) ES|QL: Adding `USER_AGENT` command (elastic#144384) ESQL: enable Generative IT after more fixes (elastic#145112) Rework FieldMapper parameter tests to not use merge builders (elastic#145213) [ESQL] Fix ORC type support gaps (elastic#145074) [Test] Unmute FollowingEngineTests.testProcessOnceOnPrimary (elastic#145192) Add PrometheusSeriesRestAction for /_prometheus/api/v1/series endpoint (elastic#144494) Prometheus labels API: add rest action (elastic#144952) ...
ncordon
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Per Prometheus API semantics, omitting the limit parameter means no limit (equivalent to limit=0). Change DEFAULT_LIMIT from 10_000 to 0 so that clients which do not pass limit receive all matching label names. The plan builder (in the parent branch) already handles limit=0 by emitting an explicit Limit(Integer.MAX_VALUE) node, avoiding the AddImplicitLimit rule's silent 1 000-row cap.
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Adds
PrometheusLabelsRestAction, the REST handler forGET /_prometheus/api/v1/labels. It wires together the plan builder and response listener from the prerequisite PRs and registers the action with the Prometheus plugin. Integration tests are covered byPrometheusLabelsRestIT.Note
This PR depends on #144950 and #144951 being merged first. It will not compile until both are merged.
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