* topology: follow a volume that moved between a server's disks
The heartbeat diff asked only whether a volume id was reported anywhere on the
node, so a volume that moved to a disk of another type stayed on the disk it
left as well. The master then held two copies of it forever: the volume count
was overstated, and GetVolumesById returned whichever disk the map iterated
first, so lookups could hand back the disk the volume had already left.
Track which disk types the heartbeat named each volume on, and treat a volume
named on another disk as absent from this one. Disk types are interned to an
index because a server reports a handful of them across hundreds of thousands
of volumes.
A volume named on two disks at once is a stale twin rather than a move, and is
still kept on both -- dropping one would tell the master a replica vanished.
Only a volume named twice on one disk type is unrepresentable, so that is now
what marks the node, rather than any repeat of an id.
* master: do not tell clients a moved volume left the node
A volume moved between a node's disks is removed from one and added to the
other, so it lands in both lists of the same heartbeat. Clients apply additions
before deletions, so the removal wins and they end up with no location for a
volume that never went anywhere.
Skip removals for volumes the node still holds, as the ec shard paths already
do, and update the topology before judging the delta removals so an unmount
that really did happen is still reported.
* trim the comments on this change to the parts that are not evident
* master: judge a volume removal on normal replicas alone
HasVolumesById answers for ec shards as well, so a replica encoded into ec
shards looked like it was still on the node and clients were never told the
normal location had gone. They hold normal and ec locations separately and
prefer the normal one from the same generation, so that location would have
gone on shadowing the shards.
Chris LuandGitHub
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