fix(frontend): use dedicated runtime to accept connection

[chenzl25]

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What's changed and what's your intention?

• Resolve Bug: Frontend hangs and can't accept new connection #16837

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[BugenZhao]

LGTM

It might still be worth noting that if all threads in worker_runtime are occupied with CPU-intensive queries, even if new connections can be accepted, they can't make any progress.

This could be significant in Cloud free-tier deployment where there's only 1 CPU core thus 1 worker threads.

Can refer to #9019 and #16693.

[chenzl25]

LGTM

It might still be worth noting that if all threads in worker_runtime are occupied with CPU-intensive queries, even if new connections can be accepted, they can't make any progress.

This could be significant in Cloud free-tier deployment where there's only 1 CPU core thus 1 worker threads.

Can refer to #9019 and #16693.

One thing I can't figure out is why using the same tokio runtime would block the listen.accept with 100% probability.

[chenzl25]

@wangrunji0408 madsim-tokio seems doesn't contain tokio::runtime::Handle

error[E0433]: failed to resolve: could not find `Handle` in `runtime`
   --> src/utils/pgwire/src/pg_server.rs:258:42
    |
258 |     let worker_runtime = tokio::runtime::Handle::current();
    |                                          ^^^^^^ could not find `Handle` in `runtime`

[BugenZhao]

One thing I can't figure out is why using the same tokio runtime would block the listen.accept with 100% probability.

I guess there's some sense of affinity mechanism for the I/O driver, as described in #9019

since tokio tends to move the IO scheduler to the same worker thread with this session, and an infinite loop starves the IO scheduler so that the main thread listening to the connection cannot be woken again! 😨

Can also refer to tokio-rs/tokio#4730.