Commit Graph
2 Commits
Author SHA1 Message Date
Chris Lu c0a9b110dd volume: stop reporting read-only volumes that are no longer here (#10867)
* volume: clear per-collection metrics when a collection leaves a server

The read-only and disk size gauges are only ever set for collections the
heartbeat still finds here, and nothing zeroes the rest. volume.balance marks a
volume read-only to move it, so the last heartbeat that saw it counts it
read-only - and if it was the collection's last volume on that server, that
count stands until the process restarts. The dashboard then shows read-only
volumes that volume.list -readonly cannot find anywhere.

Remember what each heartbeat set, and drop what is gone on the next one.

* volume: stop the read-only volume count from wrapping at 256

The per-collection counters were uint8, so a server holding 256 read-only
volumes of one collection reported zero of them.

* volume: read the read-only flags once when counting them

The heartbeat asked IsReadOnly for the verdict and then read noWriteOrDelete
and noWriteCanDelete straight off the volume, unlocked, so the reasons could
disagree with the verdict they were explaining. Take them together, under one
lock. The location is now nil-checked rather than skipped by short-circuit
evaluation, so a volume that has not joined a disk location yet stays safe.

* volume: let only a surviving volume keep its collection reported

A volume being deleted for expiry still made an entry in the read-only counts,
which is what the cleanup reads as "this collection is still here". The
collection's last volume could go and its series would stand for one more
heartbeat. Count the survivors only.

* volume: size a collection from the volumes it still has

The size totals are rebuilt from scratch every heartbeat, so subtracting a
volume that is about to be deleted took the surviving volumes' sizes down with
it: a collection keeping a small volume and losing a larger one reported the
difference, or lost its entry and kept the previous heartbeat's number.

* volume: cover the deleted bytes total in the surviving volume test

Deleted bytes are totalled the same way as sizes and were going unchecked, so
the test now leaves deleted needles on both volumes and pins that gauge too.
2026-08-21 22:33:01 -07:00
Chris Lu 3bd218e030 volume: cut idle memory at high volume counts (#10861)
* volume: start a volume's batch write worker on first use

Mounting a volume started a goroutine parked on a 128-slot channel, plus
the 128-entry batch slice it had already allocated. That is around 6.7KB
per volume the server pays whether or not the volume ever takes a write:
7231 bytes per mounted volume, of which 4101 is goroutine stack.

Only a write that asks for fsync ever reaches the worker, and a
remote-tiered or read-only volume never can. Create the channel and its
goroutine on the first such request instead, and let a write arriving
after Destroy fall back to the inline path rather than queue onto a
worker that has gone.

Measured over 20000 mounted volumes: 7231 -> 1269 bytes each.

* volume: update the heartbeat report state in place

Every heartbeat built a second map of what it was about to tell the
master, holding a freshly allocated short information message per volume,
then swapped it in over the old one -- and computed departures through a
third map of the live volume ids. A server holding 2M volumes rebuilt all
three every VolumePulsePeriod for a report that usually says nothing.

Number the heartbeats instead and mark the entry already held with the
pass that found the copy, so a quiet volume costs a map lookup and no
allocation. Departures are the entries a pass did not mark; the live-id
map is now built only when there are some, sized to them.

Measured over 10000 mounted volumes: 436 -> 196 bytes allocated per
volume per heartbeat.

* volume: fill one volume information message per heartbeat, not per volume

The heartbeat built a message for every volume held so it could hash it,
then dropped all but the few it had something to say about. At 2M volumes
that is 2M messages allocated every VolumePulsePeriod to send almost none
of them.

Fill a message the caller supplies instead, and replace it only when the
heartbeat keeps it, so a server with nothing to report fills the same one
all the way through.

Measured over 10000 mounted volumes: 196 -> 4 bytes allocated per volume
per heartbeat, and a heartbeat runs a third faster.

* volume: drop the per-volume trace from the heartbeat's status read

glog.V(4).Infof evaluates its arguments whether or not the verbosity is
on, so every volume boxed its id into a fresh interface slice on every
heartbeat: 759 of the 773 allocations a 1000-volume heartbeat made, for a
line that at this scale would print millions of unreadable rows.

Measured over 1000 mounted volumes: 4776 -> 1792 bytes and 759 -> 14
allocations per heartbeat, which no longer grows with the volume count.

* seaweed-volume: mirror the in-place heartbeat report state

Same change as the Go volume server: number the heartbeats and mark the
entry already held with the pass that found the copy, instead of building
a second map of hashes and swapping it in.

The volume snapshot must leave the reporting state as it found it, so it
keeps asking through changed() while a real heartbeat marks through
record().

* volume: refuse writes to a closed volume instead of dereferencing nil

Close and Destroy leave the needle map and data backend nil, but a caller
that already holds the volume can still reach the write path, where both
are used unguarded: a write racing a volume deletion took the server down.
syncDelete has always checked; syncWrite and the batch worker had not.

Reachable before this series and now also from the inline fallback a
durable write takes when the worker has gone.

* seaweed-volume: guard the report state with one mutex, as Go does

The full-list flag and the generation that answers it have to move
together. Split across separate atomics they cannot: a request landing
between begin's two reads returns full == false with the generation it
just raised, and one landing between commit's read and its clear is
marked answered by a heartbeat that carried no list. Either way the
resend is dropped.

Neither is reachable today -- every caller reaches this through the
store's RwLock, the flag setters under a read lock and the heartbeat
build under a write lock, so they cannot interleave. The type should not
depend on that being true two files away, and Go holds a single mutex
over exactly these fields.

* test: build the servers under test to match the harness's offset size

The mixed Go/Rust suites run both servers against one dataset, so both
have to agree on the offset width. They did not: the harness built Go
with no tags, 4-byte offsets, while the Rust crate defaults to its 5bytes
feature, and the Rust server then refused the .vif the Go server had just
written -- "bytes_offset mismatch: found 4, expected 5".

Build each side to match the offset size the test binary itself was
compiled with, so a plain `go test` and one with -tags 5BytesOffset both
get a matched pair.
2026-08-21 13:04:56 -07:00