net/http: add Transport.MaxIdleConns limit #15461
Description
There's been a long-standing TODO in net/http.Transport that says:
type Transport struct {
....
// TODO: tunable on global max cached connections
....This bug is about that.
We already have Transport.MaxIdleConnsPerHost, but it's been requested by many (and again recently) that we have a Transport.MaxIdleConns for any host.
In the process, I also noticed that we're not aggressively removing cached connections when the peer server disconnects. We only lazily clean them up from the idle structures, which means we can hold onto memory for the bufio.Readers/Writers for a long time, wasting memory.
/cc @adg