- Use postgres_backend_async throughout safekeeper.
- Use framed.rs in postgres_backend_async, similar to tokio_util::codec::Framed
but with slightly more efficient split. Now IO functions are also cancellation
safe. Also, there is no allocation in each message read anymore, and data in
read messages still directly point to input buffer without copies.
- In both safekeeper COPY streams, do read-write from the same thread/task with
select! for easier error handling.
- Tidy up finishing CopyBoth streams in safekeeper sending and receiving WAL
-- join split parts back catching errors from them before returning.
Initially I hoped to do that read-write without split at all, through polling
IO:
https://github.com/neondatabase/neon/pull/3522
However that turned out to be more complicated than I initially expected
due to 1) borrow checking and 2) anon Future types. 1) required Rc<Refcell<...>>
which is Send construct just to satisfy the checker; 2) can be workaround with
transmute. But this is so messy that I decided to leave split.
proxy stream.rs is adapted with minimal changes. It also benefits from framed.rs
improvements described above.
