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Chris Lu 938a15eb98 filer: keep a moved key on its prior owner while the ring settles (#11108)
ObjectTransaction forwards to the ring owner so one filer's per-path lock
arbitrates every writer of a key. But a ring change hands the key over before
the new owner has rebuilt the locks the prior owner still holds, so for the
cooling-off window both can grant it. LockRing.PriorOwner exists for exactly
this and nothing consulted it.

Route to the prior owner while that window is open. LockRing.WriteOwner
resolves prior-else-current under one read lock, so the pair cannot come from
different rings and name the same filer twice.

An unreachable owner fails the request rather than falling back to the current
one. gRPC reports a response lost in transit as Unavailable, indistinguishable
from a request the owner never saw, so re-sending elsewhere could re-apply what
the owner already committed; and an owner unreachable from here may be
partitioned rather than down, still serving the key to everyone else — which is
the split brain the routing exists to prevent. The window is bounded: once it
closes the ring hands the key to its new owner.

The owner resolution and the forward move into writeOwner/forwardToWriteOwner
so the next routed RPC reuses them rather than copying the block.

Claude-Session: https://claude.ai/code/session_01Fx1Hx8RqsJqHpbfbgTf4WJ
2026-09-02 19:40:53 -07:00
..
2026-04-10 17:31:14 -07:00
2026-04-10 17:31:14 -07:00