[Connection Pool]: Implement triggerGracefulShutdown #595
Description
Please summarize your feature request
Implement ConnectionPool.triggerGracefulShutdown which call graceful shutdown on all open connections and moves to shutdown state once all connections are closed.
Describe the functionality you're seeking in more detail
Another request from valkey-swift.
The cluster client in valkey-swift manages multiple connection pools and will bring up and shutdown pools as when nodes appear and disappear from the cluster. Currently the client has to run a force shutdown on the connection pool which closes all the connections regardless of whether requests are still in progress. Ideally when shutting down a connection pool we should be able to trigger a graceful shutdown which waits until current requests are served.
The connection manager state machine has a stub for triggerGracefulShutdown which fatalErrors. It would be good to implement it.
Have you considered any alternatives?
No response