HTTP client: Expose maximum time to keep alive idle connection with persistent connections

Hi there!

Good job with taking care of https://github.com/reactphp/http/issues/468. Having the ability to use persistent connections is definitely a game changer for some use cases!

I was wondering if it would be a good idea to expose the $maximumTimeToKeepAliveIdleConnection variable (https://github.com/reactphp/http/blob/1.x/src/Io/ClientConnectionManager.php line 39) in order to support ongoing communication with a webserver, especially with REST API and architectures such as OpenResty.

I'm aware it represents some work as a lot of objects have to be exposed (client, transaction, sender, etc.), but I was wondering if it would be worth it for that particular use case. I noticed an improvement of 100ms per chained request on average by changing the timeout from 1ms to 10s.

Is there a reason why connections are considered idle only under 1ms? I think it might be too low (which is the reason why I'm flagging this as an issue and not a suggestion).

Thanks a lot for ReactPHP!

Start with src/Io/ClientConnectionManager.php, where $maximumTimeToKeepAliveIdleConnection is defined, then trace how the client, transaction, and sender objects expose connection configuration. Done means the maximum idle-connection time can be configured for persistent HTTP client communication without requiring direct edits to the connection manager.