feat(scanner): expose prefix-level bucket usage via admin API
The scanner's per-bucket, per-set usage caches already hold a path-keyed
prefix tree, but dui() flattened it only to bucket names — consoles and
operators had no way to ask "what does this prefix hold" without an S3
listing sweep (rustfs/backlog#1872, MinIO loadPrefixUsageFromBackend
parity).
Add:
- data-usage: prefix_usage_in_cache — a shared aggregation over the
entry map (arbitrary prefix, full counters, one-level sub-prefix
breakdown with names recovered from the literal-path cache keys),
hardened like the scanner's checked flatten: cycles, dangling child
links, over-deep trees, and overflowing counters yield None rather
than unbounded recursion or wrapped totals.
- ecstore: ECStore::all_set_disks — iterate every erasure set so a
query can read each set's own cache copy; the hash-routed store path
would always land on one set.
- scanner: bucket_prefix_usage — per-set loads (5s budget each, a slow
set degrades to not-reporting instead of stalling the caller),
merged across sets with partial/compacted/truncated flags, served
from a bounded 30s cache (128 entries, hard-capped) that bucket
writes invalidate through the dirty-usage hook.
- admin: GET /rustfs/admin/v3/usage/{bucket}?prefix=&max-entries=
behind the same any-of gate as datausageinfo (DataUsageInfoAdminAction
OR ListBucketAction), rejecting unknown query parameters and
clamping max-entries to 1..=10000. Route registered in the policy
table (deferred MultipleActions, matching datausageinfo) and the
route matrix test.
Closesrustfs/backlog#1872.
Co-authored-by: heihutu <heihutu@gmail.com>
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