Updates `compute_tools` and `compute_api` crates to edition 2024. We
like to stay on the latest edition if possible. There is no functional
changes, however some code changes had to be done to accommodate the
edition's breaking changes.
The PR has three commits:
* the first commit updates the named crates to edition 2024 and appeases
`cargo clippy` by changing code.
* the second commit performs a `cargo fmt` that does some minor changes
(not many)
* the third commit performs a cargo fmt with nightly options to reorder
imports as a one-time thing. it's completely optional, but I offer it
here for the compute team to review it.
I'd like to hear opinions about the third commit, if it's wanted and
felt worth the diff or not. I think most attention should be put onto
the first commit.
Part of #10918
compute_ctl is mostly written in synchronous fashion, intended to run in
a single thread. However various parts had become async, and they
launched their own tokio runtimes to run the async code. For example, VM
monitor ran in its own multi-threaded runtime, and apply_spec_sql()
launched another multi-threaded runtime to run the per-database SQL
commands in parallel. In addition to that, a few places used a
current-thread runtime to run async code in the main thread, or launched
a current-thread runtime in a *different* thread to run background
tasks.
Unify the runtimes so that there is only one tokio runtime. It's created
very early at process startup, and the main thread "enters" the runtime,
so that it's always available for tokio::spawn() and runtime.block_on()
calls. All code that needs to run async code uses the same runtime.
The main thread still mostly runs in a synchronous fashion. When it
needs to run async code, it uses rt.block_on().
Spawn fewer additional threads, prefer to spawn tokio tasks instead.
Convert some code that ran synchronously in background threads into
async. I didn't go all the way, though, some background threads are
still spawned.
I'm trying to debug a situation with the LR benchmark publisher not
being in the correct state. This should aid in debugging, while just
being generally useful.
PR: https://github.com/neondatabase/neon/pull/9265
Signed-off-by: Tristan Partin <tristan@neon.tech>
There was a tricky race condition in compute_ctl, that sometimes makes
configurator skip updates. It makes a deadlock because:
- control-plane cannot configure compute, because it's in
ConfigurationPending state
- compute_ctl doesn't do any reconfiguration because
`configurator_main_loop` missed notification for it
Full sequence that reproduces the issue:
1. `start_compute` finishes works and changes status
`self.set_status(ComputeStatus::Running);`
2. configurator received update about `Running` state and dropped the
mutex lock in the iteration
3. `/configure` request was triggered at the same time as step 1, and
got the mutex lock
4. same `/configure` request set the spec and updated the state to
`ConfigurationPending`, also sent a notification
5. next iteration in configurator got the mutex lock, but missed the
notification
There are more details in this slack thread:
https://neondb.slack.com/archives/C03438W3FLZ/p1727281028478689?thread_ts=1727261220.483799&cid=C03438W3FLZ
---------
Co-authored-by: Alexey Kondratov <kondratov.aleksey@gmail.com>
With this commit one can request compute reconfiguration
from the running `compute_ctl` with compute in `Running` state
by sending a new spec:
```shell
curl -d "{\"spec\": $(cat ./compute-spec-new.json)}" http://localhost:3080/configure
```
Internally, we start a separate configurator thread that is waiting on
`Condvar` for `ConfigurationPending` compute state in a loop. Then it does
reconfiguration, sets compute back to `Running` state and notifies other
waiters.
It will need some follow-ups, e.g. for retry logic for control-plane
requests, but should be useful for testing in the current state. This
shouldn't affect any existing environment, since computes are configured
in a different way there.
Resolvesneondatabase/cloud#4433
