Commit Graph
4 Commits
Author SHA1 Message Date
Chris Lu eed3c27d15 volume: cut the memory a server holding millions of volumes still uses (#10999)
* volume: stop the .vif guard depending on which entry the scan handed over

A volume has both an .idx and a .vif, and loadExistingVolume skipped a .vif
next to an .ecx as EC shard metadata. That was only ever correct because
os.ReadDir sorted .idx ahead of .vif: an interrupted encode, where the .idx is
still there, has to reach validateEcVolume to be reclaimed. Ask for the .idx
instead of trusting the order.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* volume: walk volume directories in batches instead of listing them whole

os.ReadDir builds, and sorts, a slice of every entry before the caller sees
the first one. A disk holding millions of volumes has a .dat, .idx and .vif
per volume, so each startup scan costs hundreds of MB of peak heap that the
runtime is slow to hand back -- and there are several of them before the
first volume loads.

Walk in batches instead, and keep only the entries each scan acts on:
loadAllEcShards now sorts and stats the shard and index files alone rather
than every file on the disk.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* volume: skip the sibling-.dat scan when no EC volume is loaded

pruneIncompleteEcWithSiblingDat only ever prunes EC volumes that are loaded,
but it first walks every disk and keys a map by every .dat on the server. On
a store with no EC volumes at all that is millions of map entries built to
answer no question.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* volume: stop keeping a departure message for every volume

The report state held a VolumeShortInformationMessage per volume copy so a
departure could be named, but almost no volume ever departs. Hold a handle to
the identity instead -- volumes share very few distinct ones -- and build the
message on the way out.

Measured over a populated report state: 195 -> 83 bytes per volume.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* rust volume: stop keeping a whole volume message per volume held

The send loop kept a VolumeInformationMessage for every volume just to notice
mounts and unmounts, and rebuilt the map from scratch on every beat. Keep the
identity a delta names, which is what the Go report state keeps for the same
reason.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* rust volume: keep only the EC files the shard scan acts on

load_all_ec_shards named every file on the disk twice -- once in the dedup set
and once in the sorted vector -- before deciding it only wanted .ec?? and .ecx.
Filter while reading instead. Mirrors the same change in loadAllEcShards.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy

* volume: share the strings every .vif repeats

A tiered volume's .vif names its replication and its backend, and every decode
allocates a fresh copy, so a server holding millions of them holds millions of
copies of the same handful of names. Route them through the interning table
the volume info decode already uses. The remote key names one volume and is
left alone.

Claude-Session: https://claude.ai/code/session_01NWpFUwAJcR2KUENrhLc9Sy
2026-08-27 22:25:15 -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
Chris Lu a2ffc7aadf heartbeat: keep the master current through collection churn (#10657)
* heartbeat: name departed volumes in delta heartbeats

* master: release the lookup index with a deleted collection

* master: keep a fresh grow safe from the report that raced it

* volume: name the volumes a deleted collection took with it

Deleting a collection left the master to work out what went by omission from
the next full volume list, which it no longer gets: heartbeats carry the whole
list only when the master asks for it. The volumes a bucket's churn creates and
destroys between two of those requests are never named in either direction, so
the master keeps counting their slots as occupied and a cluster that creates
and drops collections quickly runs its free-slot accounting dry -- assigns fail
with no free volumes left while the disk holds a handful of volumes.

The destroy path already knows exactly which volumes it removed, so send them
down the same channel every other deletion uses.

* rust: name the volumes a deleted collection took with it

Mirrors the Go volume server. The notify path derives its deltas by diffing
snapshots, so a collection delete that does not wake it is invisible until the
master next asks for the whole list.
2026-08-08 20:23:10 -07:00
Chris Lu ce7d388639 heartbeat: send only the volumes that changed (#10640)
* pb: let a heartbeat carry only the volumes that changed

A partial list cannot travel in volumes: a master that did not understand it
would read the absences as deletions. So changes get their own field, used only
once the master has said it compares digests and can tell when it has fallen
behind.

* master: apply the volumes a heartbeat reports as changed

Only the named volumes are touched. A full report says the server holds exactly
these; a changed report says nothing about the ones it leaves out, so absence
must not read as removal.

Also advertises that the master compares digests, which is what lets a server
stop sending its whole list. Advertising it once per connection means a server
reconnecting to a master that does not is back to full lists straight away.

* volume: send only the volumes that changed once the master accepts them

The whole list goes on every heartbeat until the master says it compares
digests, and again whenever it asks, so a master that cannot tell when it has
fallen behind never has to.

has_no_volumes stays derived from a full list alone. Deriving it from what a
heartbeat happens to carry would make a quiet one read as a server that had
lost every volume, and the master would drop them all.

The digest still covers every volume held rather than the ones sent, which is
what lets the master confirm that applying the changes left it current.

Reporting state is per-connection: a server that reconnects, or reaches a
different master, starts again from the full list.

* volume: let the zero reporting state stand for having told no master anything

A Store built as a literal, which tests do, left the reporting state nil and
panicked on the first heartbeat. As a value its zero form already means nothing
has been reported to anyone, which is exactly the state that sends the whole
list.

* rust: send only the volumes that changed once the master accepts them

Mirrors the Go volume server, with one hazard the Go side does not have: mount
and unmount deltas here are derived by diffing successive heartbeats, so a
heartbeat that carries a partial list would report every volume it left out as
unmounted. Collecting now returns the full set alongside the message, and every
site that diffs uses that rather than what went on the wire.

* volume: do not let a full-list request be lost to the heartbeat it raced

The request arrived while a heartbeat was already being built as a delta, and
committing that heartbeat cleared it, so the master waited for another digest
mismatch before asking again. Count the requests and clear only the one the
heartbeat answered.

* rust: stop marking volumes reported by a heartbeat that is thrown away

The state-notify path collected a heartbeat only to diff its volume list, then
sent a delta message of its own and dropped the one it had collected. Once
collecting recorded what the master had been told, every mount or unmount
silently marked the changed volumes as sent, and the master learned of them
only after a digest mismatch.

Snapshotting no longer records anything, and no longer expires ec volumes
whose deletion that path was already discarding.

* master: announce only the volumes a change actually brought

Every changed volume was broadcast as a new location. Volumes grow constantly
and growth moves no location, so on a busy cluster that told every connected
client about volumes it could already reach, filling bounded broadcast queues
and pushing out the topology updates that matter.

* master: ask for the full list when only one can repair the master

Delta heartbeats stop the full report, and with it the only thing that
re-registers a volume the lookup index lost. The volume server cannot see that
divergence and its digest cannot show it, so the master now checks its own two
indexes agree and asks for the list when they do not.

A node reporting one volume id twice is kept on full lists for the same reason
rather than merely skipped: its digest can never be verified, so nothing else
would tell the master what it had stopped holding.

* master: keep the volume options on every heartbeat response

A volume server takes them from whatever response arrives, and preallocate is a
bare bool with no way to tell off from unmentioned. A response sent to ask for
the volume list therefore turned preallocation off until the server reconnected.

Responses sent mid-stream now start from the configured options rather than
being built field by field.

* master: announce a volume the lookup index had lost

Repairing the index makes the volume servable again, but clients were told it
went when the node dropped out and nothing told them otherwise: the disk map
still held it, so it did not count as an arrival.

Reaching the lookup index is what makes a volume servable, so recovering an
entry there is an arrival as far as clients are concerned, on both the full
report and the changed-volume path.
2026-08-07 23:36:28 -07:00