This PR implements solution proposed in scylladb/scylladb#24481
Instead of terminating connections immediately, the shutdown now proceeds in two stages: first closing the receive (input) side to stop new requests, then waiting for all active requests to complete before fully closing the connections.
The updated shutdown process is as follows:
1. Initial Shutdown Phase
* Close the accept gate to block new incoming connections.
* Abort all accept() calls.
* For all active connections:
* Close only the input side of the connection to prevent new requests.
* Keep the output side open to allow responses to be sent.
2. Drain Phase
* Wait for all in-progress requests to either complete or fail.
3. Final Shutdown Phase
* Fully close all connections.
Fixesscylladb/scylladb#24481Closesscylladb/scylladb#24499
* https://github.com/scylladb/scylladb:
test: Set `request_timeout_on_shutdown_in_seconds` to `request_timeout_in_ms`, decrease request timeout.
generic_server: Two-step connection shutdown.
transport: consmetic change, remove extra blanks.
transport: Handle sleep aborted exception in sleep_until_timeout_passes
generic_server: replace empty destructor with `= default`
generic_server: refactor connection::shutdown to use `shutdown_input` and `shutdown_output`
generic_server: add `shutdown_input` and `shutdown_output` functions to `connection` class.
test: Add test for query execution during CQL server shutdown
c41f0e6da9