I'm seeing "http2: no cached connection was available" failures from http.Client when I start many (~hundreds) requests at once. (This issue was also posted to golang-nuts@ in April <https://groups.google.com/d/topic/golang-nuts/0YEWYwBOJPI/discussion>, with no response)
I may not understand correctly, but I thought this kind of usage was fine with HTTP 1.1 and net/http, because the spec mandates a max number of outgoing connections to any given host, so http.Client throttles open connections and effectively queues requests past that. The http2 package seems not to do the same. That might be correct according to the spec (I don't know), but makes using http.Client weird -- I need to rate limit its usage if the server is HTTP 2, but it does rate limiting for me if the server is HTTP 1.1. Is my understanding correct? Is this a bug? Is the expectation that my app should be rate limiting, regardless of server version? Also, It seems the error being returned is exported <https://godoc.org/golang.org/x/net/http2#pkg-variables> in the http2 package, but is not exported in the bundled version <https://golang.org/src/net/http/h2_bundle.go#L4775> in net/http. If it was exported, I think I could at least retry on my own, but perhaps that's not the intended usage anyway. I wrote this program <https://play.golang.org/p/zKthX7Y9RW> hitting https://www.google.com/ to demonstrate -- here are a few run results: $ GODEBUG=http2client=0 go run /tmp/foo.go $ GODEBUG=http2client=0 go run /tmp/foo.go $ GODEBUG=http2client=0 go run /tmp/foo.go $ GODEBUG=http2client=0 go run /tmp/foo.go $ GODEBUG=http2client=0 go run /tmp/foo.go $ GODEBUG=http2client=1 go run /tmp/foo.go Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available ... $ GODEBUG=http2client=1 go run /tmp/foo.go Get https://www.google.com/: http2: no cached connection was available $ GODEBUG=http2client=1 go run /tmp/foo.go $ GODEBUG=http2client=1 go run /tmp/foo.go Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available ... $ GODEBUG=http2client=1 go run /tmp/foo.go Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available Get https://www.google.com/: http2: no cached connection was available ... -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
