* master: stream volume listings
A listing of 800k volumes is 36MB on the wire but 305MB as messages, and the
master built all of it, then held it while grpc encoded it. Two of those at
once is most of a small master's heap, and the maintenance scanner asks every
30 minutes.
The topology goes out first, listing nothing, then its volumes in batches, so
the master holds a batch rather than a cluster: 341MB of live heap for one
listing becomes 4.4MB. It allocates much the same either way -- what changes is
how much of it has to be live at once, which is what sets the heap ceiling.
Batches are built under their disk's lock and sent outside it, so a slow reader
stalls the stream rather than the topology. They therefore do not share one
instant, which a single listing did not either: it takes each disk's lock in
turn, so a volume moving during either can be seen twice or not at all.
The client helper hides which kind of master answered: one too old for the
stream is asked the old way and its reply cut into the same batches. Either way
the topology handed over lists no volumes, so a caller cannot come to depend on
finding them there.
* admin: stream the listing the maintenance scan reads
It asks for every volume in the cluster every 30 minutes. Reassembling it
client-side keeps the scan identical -- ActiveTopology splits disks by the
disk ids on the volumes, so it needs them in the topology -- while the master
no longer builds the whole reply to send it.
* topology: report a disk id that does not depend on map order
A topology disk that fronts several physical disks took its reported id from
whichever volume the map yielded first, so two listings of an unchanged disk
could disagree. Take the smallest instead.
* topology: test that a streamed listing rebuilds to the whole one
The callers that stream now rebuild the listing from a topology sent without
volumes plus the batches after it, so that has to come out the same as being
sent it whole, at every batch size and under a filter.
* clients: stream the volume listings that ask for everything
The dashboard's list and export pages, the collection and ec shard pages, the
topology view, the worker metrics and two shell commands each asked the master
to build all 800k volumes into one reply. They read the same listing as before,
rebuilt on their side, so the master no longer holds it.
The three that already ask for one volume or one collection stay as they are:
their replies are small, and streaming one costs a round trip to say so.
A master decides nothing from it. Every caller that read it was asking whether
a volume is remote, which the backend name answers, and the value itself is
reported on demand by the server holding the volume, through the volume info in
ReadVolumeFileStatus.
It is also the one string here that cannot be shared: unique per volume, so
unlike the collection and backend names it carries its own characters for every
volume a master tracks.
VolumeInfo goes from 136 bytes to 120. 800k volumes registered from a heartbeat
that has been over the wire go from 214 to 163 B/volume when tiered.
The volume server's own status page keeps showing the key, now read from the
volume it holds rather than relayed through a master, which is also where the
other volume server implementation reads it.
The heartbeat digest drops it on the same grounds: a change to something the
master does not hold cannot make its copy stale. Both implementations and their
shared vectors move together, and the field-coverage test now names what is
deliberately not retained rather than being loosened.
Adds an "Export All (JSON)" button on the Cluster Volumes page that pulls
the whole cluster's volume list from the master in one call, a superset of
volume.list. Beyond the table columns it carries garbage and fullness
ratios, modified time, compact revision, remote tiering keys, per-disk
capacity counts, EC shard sizes with file/delete counts, and a cluster-wide
duplicate-volume-id scan. Honors the active collection filter. The existing
per-page CSV export stays as "Export Page".
Chris LuandGitHub