This is a full switch, fs io operations are also tokio ones, working through
thread pool. Similar to pageserver, we have multiple runtimes for easier `top`
usage and isolation.
Notable points:
- Now that guts of safekeeper.rs are full of .await's, we need to be very
careful not to drop task at random point, leaving timeline in unclear
state. Currently the only writer is walreceiver and we don't have top
level cancellation there, so we are good. But to be safe probably we should
add a fuse panicking if task is being dropped while operation on a timeline
is in progress.
- Timeline lock is Tokio one now, as we do disk IO under it.
- Collecting metrics got a crutch: since prometheus Collector is
synchronous, it spawns a thread with current thread runtime collecting data.
- Anything involving closures becomes significantly more complicated, as
async fns are already kinda closures + 'async closures are unstable'.
- Main thread now tracks other main tasks, which got much easier.
- The only sync place left is initial data loading, as otherwise clippy
complains on timeline map lock being held across await points -- which is
not bad here as it happens only in single threaded runtime of main thread.
But having it sync doesn't hurt either.
I'm concerned about performance of thread pool io offloading, async traits and
many await points; but we can try and see how it goes.
fixes https://github.com/neondatabase/neon/issues/3036
fixes https://github.com/neondatabase/neon/issues/3966
I've added logs for broker push duration after every iteration in https://github.com/neondatabase/neon/pull/4142. This log has not found any real issues, so we can replace it with metrics, to slightly reduce log volume.
LogQL query found that pushes longer that 500ms happened only 90 times for the last month. https://neonprod.grafana.net/goto/KTNj9UwVg?orgId=1
`{unit="safekeeper.service"} |= "timeline updates to broker in" | regexp "to broker in (?P<duration>.*)" | duration > 500ms`
Add essential safekeeper and pageserver::walreceiver metrics. Mostly
counters, such as the number of received queries, broker messages,
removed WAL segments, or connection switches events in walreceiver.
Also logs broker push loop duration.
Refactors walsenders out of timeline.rs to makes it less convoluted into
separate WalSenders with its own lock, but otherwise having the same structure.
Tracking of in-memory remote_consistent_lsn is also moved there as it is mainly
received from pageserver.
State of walsender (feedback) is also restructured to be cleaner; now it is
either PageserverFeedback or StandbyFeedback(StandbyReply, HotStandbyFeedback),
but not both.
This API is rather pointless, as sane choice anyway requires knowledge of peers
status and leaders lifetime in any case can intersect, which is fine for us --
so manual elections are straightforward. Here, we deterministically choose among
the reasonably caught up safekeepers, shifting by timeline id to spread the
load.
A step towards custom broker https://github.com/neondatabase/neon/issues/2394
"cargo clippy" started to complain about these, after running "cargo
update". Not sure why it didn't complain before, but seems reasonable to
fix these. (The "cargo update" is not included in this commit)
Mitigates latency fee, making push throughput 1-1.5 order of magnitude bigger.
Also make leases per timeline, not per whole safekeeper, avoiding storing
garbage in etcd for deleted timelines while safekeeper is alive.
I still don't like the surroundings and feel we'd better get away without using
election API at all, but this is a quick fix to keep CI green.
ref #1815
- Uncomment accidently `self.keep_alive.abort()` commented line, due to this
task never finished, which blocked launcher.
- Mess up with initialization one more time, to fix offloader trying to back up
segment 0. Now we initialize all required LSNs in handle_elected,
where we learn start LSN for the first time.
- Fix blind attempt to provide safekeeper service file with remote storage
params.
Separate task is launched for each timeline and stopped when timeline doesn't
need offloading. Decision who offloads is done through etcd leader election;
currently there is no pre condition for participating, that's a TODO.
neon_local and tests infrastructure for remote storage in safekeepers added,
along with the test itself.
ref #1009
Co-authored-by: Anton Shyrabokau <ahtoxa@Antons-MacBook-Pro.local>
Remove when it is consumed by all of 1) pageserver (remote_consistent_lsn) 2)
safekeeper peers 3) s3 WAL offloading.
In test s3 offloading for now is mocked by directly bumping s3_wal_lsn.
ref #1403
Arseny Sher
Arthur Petukhovsky
Kirill Bulatov
Heikki Linnakangas
chaitanya sharma
Kirill Bulatov