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Chris LuandGitHub
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* Reconstruct an EC shard from the shards already on this server recoverOneRemoteEcShardInterval only ever fanned out to the cached shard locations, so a server holding shards of the volume still fetched them over gRPC from itself -- and when the peers were unreachable it could not reconstruct at all, even holding the whole volume on local disk. Seed the Reed-Solomon buffers from the locally mounted shards first; each one is a peer round trip, and an interval-sized buffer, the fan-out no longer needs. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Fetch only the EC shards reconstruction still needs The recovery fan-out read every surviving shard, so a 10+4 volume pulled 13 interval-sized buffers to feed Reed-Solomon 10 -- a third more memory held, and a third more load asked of peers that were, by definition, already having trouble. Fetch what is missing, and widen only when some of those reads fail. A shard reporting the needle deleted ends the walk: the rest would only answer the same. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Bound the bytes EC recovery holds in flight Recovery is the one read path that multiplies the served bytes: it holds an interval-sized buffer per shard until Reed-Solomon runs, and a peer that is slow to fail keeps them all alive for the whole gRPC timeout. Nothing bounded how many of those fan-outs ran at once, so a transient problem between volume servers turned every read into a DataShards-fold allocation and the server died of it -- 64 concurrent 4MB intervals pin 3.6GB, and that is a small burst. Charge each recovery against a process-wide budget, so a burst queues on the semaphore instead of on the heap. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Answer a deleted EC needle as deleted, not as a failed recovery A holder reporting the needle deleted is authoritative: deletes are never invented and never undone. Recovery already collected that flag, then dropped it on the branch where too few shards came back -- so a read of a deleted needle that had to recover surfaced as "cannot recover shard", and the volume server answered 500 where it owed a 404. Carry the flag out of the shortfall, and let it decide ahead of the error it came with. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Check the encode run of a locally seeded EC shard in Rust The Rust recovery seeded Reed-Solomon straight from the mounted shards, without the encode-run check the remote reads and Go's readLocalEcShardInterval both apply. A volume remounted from a newer encode between the read's snapshot and its recovery would have fed mixed-generation bytes into the reconstruction. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Say what the recovery budget actually guarantees Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN * Seed Rust EC recovery from shards on every local disk find_ec_volume returns the first disk's EcVolume, so a reconciled volume whose shards are split across data dirs had the siblings ignored and could report "cannot recover" while holding enough shards locally. Resolve each shard together with the disk that owns it, the way Go's recovery already does, and check that owner's encode run. Claude-Session: https://claude.ai/code/session_01SM5ARdPvFcnvGWNpBPgNRN