Implements the MinIO active-active read-proxy protocol (P1-5 of the
replication compatibility review): when a GET/HEAD/GetObjectTagging/
PutObjectTagging/DeleteObjectTagging request fails locally with
not-found and the bucket has replication targets, the request is proxied
to the targets in rule order, mirroring bucket-replication.go
proxyGetToReplicationTarget/proxyHeadToRepTarget/proxyTaggingToRepTarget.
Protocol surface:
- Anti-loop: inbound {x-rustfs-,x-minio-}source-proxy-request is parsed
into ObjectOptions (proxy_request + proxy_header_set, matching MinIO
ProxyRequest/ProxyHeaderSet); a request carrying the marker with ANY
value is never re-proxied. Outbound client proxy calls send the marker
as "true"; replication worker convergence HEADs send it as "false" so
a peer's proxy layer cannot answer a convergence check by proxying
back to the source (which would fake Completed without a PUT).
- Target selection: new replication_proxy.rs get_proxy_targets — empty
when the marker is set, versioning is suspended, or no replication
config; otherwise filter_target_arns -> TargetClient lookup, skipping
targets with proxying disabled.
- TargetClient gains head_object_for_proxy/get_object (streaming) and
the three tagging calls. Proxy calls never send the replication-check
SSE-C exemption header; customer SSE-C keys are forwarded verbatim so
the target performs real decryption. Conditional (If-*) headers are
not forwarded (MinIO parity); Range and part_number are, with
parts_count/tag_count/storage_class/expiration passed through.
- Metrics: proxy counters now count only real client proxy traffic,
MinIO-aligned (one total per proxied request, one failed when no
target served it). The previous misattributed counters — replication
worker HEAD/PUT (#2672) and local tagging operations (#2682) — are
removed; ReplProxyMetric now maps the tagging counters instead of
dropping them.
e2e (fake_s3_target extended with tagging + header journaling): proxied
GET body + outbound header contract (marker present, no
replication-check, SSE-C passthrough), HEAD, anti-loop 404 with zero
outbound requests, GetObjectTagging, and metric mapping unit tests.
Rolling note: proxying only activates for buckets with replication
targets; requests carrying the marker keep pre-upgrade behavior.
Refs rustfs/backlog#1675 (P1-5)
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