* ec.balance: spread concurrent shard moves over target nodes
The planner gives every freshly encoded volume the same target order, so
running each volume's moves in plan order sends all concurrent copies to the
same node while the other nodes idle. Pick, among the volumes not already
moving, the pending move whose target receives the fewest moves right now.
One volume still never has two moves at once, and moves of one shard keep
their plan order.
* ec.balance: let a move into a node wait for the move of its volume leaving it
The planner counts the slot an outgoing shard frees as room for a later
incoming shard of the same volume, and the receiver refuses a shard it has no
slot for. Make the spread tests deterministic: hold the first moves until all
have started, and check that errors of several volumes are all returned.
* ec.balance: pin that the spread moves run concurrently and in plan order without parallelism
* shell: move ErrorWaitGroup to weed/util
* shell: remove unused CandidateEcNode and EcRack types
* ec: extract EC orchestration logic from weed/shell into weed/ec
Move the EC node/topology model, balance engine, encode pipeline, decode
pipeline, and rebuild engine into a new weed/ec package so shell commands
and maintenance workers can share the logic. Shell commands keep flag
parsing and delegate through a small ec.Env (dial option, topology fetch,
volume locations, lock check). Tests move along with the code.
* shell: remove unused proportional-rebalance type stubs
* ec: move scrub, replication check, and shard unmount engines into weed/ec
* worker: share the EC generation-aware shard counter from weed/ec
* ec: gofmt
* shell: drop EC aliases with no remaining callers
* ec: guard a missing topology hook and nil disk entries in topology helpers
* ec: drop trailing newlines from decode error strings
* ec: re-check the shell lock before applying shard unmounts
* shell: trim -node entries in ec.scrub
Anton Rozanov