Add cortex_ingester_tsdb_head_max_timestamp metric#7694
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Re-export the TSDB head max timestamp (prometheus_tsdb_head_max_time) from the ingester per user. This helps investigate ingestion issues such as out-of-bounds (sample too old) errors by making the per-tenant TSDB head max time visible. Signed-off-by: Ben Ye <benye@amazon.com>
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danielblando
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Jul 17, 2026
SungJin1212
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Jul 18, 2026
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What this PR does:
TSDB exposes the max timestamp of the head block via
prometheus_tsdb_head_max_time, but the Cortex ingester did not re-export it per tenant. This PR adds a newcortex_ingester_tsdb_head_max_timestampmetric (with auserlabel) that re-exports the TSDB head max timestamp per user, following the existing re-export pattern inpkg/ingester/metrics.go(aggregated with max across TSDBs viaSendMaxOfGaugesPerUser). The value is in milliseconds since epoch, matching the unit Cortex uses for the TSDB head.This improves debuggability for ingestion issues: for example, when investigating out-of-bounds ("sample too old") write errors, operators can now directly see each tenant's head max time and compare it against incoming sample timestamps.
Which issue(s) this PR fixes:
N/A
Checklist
make docproduces no changes)CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX]docs/configuration/v1-guarantees.mdupdated if this PR introduces experimental flags (N/A — no flags introduced)