Add options to set h2 keepalive_timeout?

[taikulawo]

We want close non-active connection to avoid fd run out. https://nginx.org/en/docs/http/ngx_http_core_module.html#keepalive_timeout

I can open a PR if you accept.

1. increment number when there has stream https://github.com/nginx/nginx/blob/43191be96fb5f425710400e0064c0f2d285a352d/src/http/v2/ngx_http_v2.c#L3097
2. when hit timeout, check whether has stream active, or close h2 connection. https://github.com/nginx/nginx/blob/43191be96fb5f425710400e0064c0f2d285a352d/src/http/v2/ngx_http_v2.c#L629

[seanmonstar]

h2 doesn't use Tokio's runtime types, like the timer, so that it can be portable to other runtimes.

We could probably scope out how to add it to hyper, which has a generic timer type.

[taikulawo]

But how to add keepalive timeout where we don't rely on hyper, just use h2?

[taikulawo]

maybe we could find the way without use tokio?

[seanmonstar]

I think it can be done almost entirely outside of h2. Set up a sleep(), and when it wakes up, check if there's active streams. I think the only thing missing from h2 is some sort of Connection::active_streams() -> usize method.

[taikulawo]

when sleep wake up? I don't know where to setup sleep.

[taikulawo]

if timeout is 60s, we should only time start when there no.active streams. but there no callback to me to start

[taikulawo]

I have implement active prototype