A key that cannot be described was handled two incompatible ways. Vault KV2 swallowed every describe failure and dropped the key from the page, so a damaged or newer-format record silently disappeared from the operator's inventory and from the deletion sweep's census. Local failed the whole listing instead, so one bad record stopped every scheduled deletion on the node for as long as the damage lasted. Both force a per-key problem into a whole-page answer.
ListKeysResponse now carries unreadable_key_ids, and the backends that read local key records classify per-key failures in one place: KeyNotFound is a concurrent deletion and is skipped, a material-level error names the key on the page, and anything else fails the listing, because it says nothing about a particular key and reporting it as key damage would turn a backend outage into a false data-loss alarm. A listing that covered the entire key set and found nothing readable still fails, since an empty page there is indistinguishable from a deployment with no keys; the guard is scoped to a page with no successor so a damaged key can never strand the keys behind it. The deletion sweep destroys the expired keys it can read, counts the unreadable ones, and withholds its lifecycle gauges rather than publishing a census over a key set it did not fully see.
Vault Transit needs the same treatment and is easy to miss: its per-key metadata records live in KV2 too, so folding every non-404 failure into a backend error left its per-key classification unreachable and one metadata record written by a newer build still failed every listing on the node.
Vault KV2 record reads gain the typed errors this needs: an unparseable body is MaterialCorrupt and an absent data envelope is MaterialMissing, where both were previously indistinguishable from Vault being unreachable. Only the parse failure's category and position are reported, because serde's own message embeds the offending scalar and that message reaches a log line and an admin HTTP body.
The admin list handlers refuse a malformed limit with 400 instead of silently substituting the default page size, and every page is capped at 1000 where it is cut, so a single request can no longer fan out one metadata lookup per key without bound. The four operation-level KMS metrics gain a backend label, since operation names are shared across backends and a Transit latency regression was previously indistinguishable from an AWS one. The Static backend captures its reported creation date once instead of reading the clock on every describe and list. POST /kms/clear-cache gains a named response type with an unchanged wire shape.
* fix(kms): persist and report the Vault KV2 key rotation timestamp
The rotation-age gauge reads KeyInfo::rotated_at and falls back to
created_at when it is absent. The KV2 backend never persisted a rotation
time and hardcoded None in describe_key, so a key rotated many times and
a key that was never rotated reported the same age.
Record the rotation time on the same check-and-set write that switches
the current version, and report the stored value from describe_key and
from the recovered-create path. Records written before the field existed
keep deserializing and stay unstamped: no timestamp is invented for a
rotation this node cannot vouch for.
* test(kms): cover Vault KV2 rotation timestamp persistence and legacy records
* docs(kms): describe KMS configuration convergence as implemented
* docs(kms): document the landed KMS metric families and narrow the gaps list
* docs(kms): state that no request field sets the cache metrics switch
* docs(kms): correct the describe_key cache divergence bound
Add a Grafana dashboard for the four KMS backend operation metrics
emitted at the policy choke point, Prometheus alert rules with
conservative default thresholds (pending staging baseline calibration),
and an operations runbook documenting the metric contract and the
response procedure for each alert. Register the new alert rules file in
the observability READMEs.
Refs rustfs/backlog#1584 (part of rustfs/backlog#1562)
Zhengchao An