net/http: add HTTP2Config.StrictMaxConcurrentRequests

Add a field to HTTP2Config controlling how we behave when an HTTP/2
connection reaches its concurrency limit.

This field will have no effect until golang.org/x/net/http2 is
updated to make use of it, and h2_bundle.go is updated with the
new http2 package.

For #67813

Change-Id: Ic72a0986528abb21649f28e9fe7cf6e1236b388d
Reviewed-on: https://go-review.googlesource.com/c/go/+/615875
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Nicholas Husin <nsh@golang.org>
Reviewed-by: Nicholas Husin <husin@google.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/src/net/http/http.go b/src/net/http/http.go
index 0f9165bf03..e7959fa3b6 100644
--- a/src/net/http/http.go
+++ b/src/net/http/http.go
@@ -235,10 +235,23 @@ type Pusher interface {
 // both [Transport] and [Server].
 type HTTP2Config struct {
 	// MaxConcurrentStreams optionally specifies the number of
-	// concurrent streams that a peer may have open at a time.
+	// concurrent streams that a client may have open at a time.
 	// If zero, MaxConcurrentStreams defaults to at least 100.
+	//
+	// This parameter only applies to Servers.
 	MaxConcurrentStreams int
 
+	// StrictMaxConcurrentRequests controls whether an HTTP/2 server's
+	// concurrency limit should be respected across all connections
+	// to that server.
+	// If true, new requests sent when a connection's concurrency limit
+	// has been exceeded will block until an existing request completes.
+	// If false, an additional connection will be opened if all
+	// existing connections are at their limit.
+	//
+	// This parameter only applies to Transports.
+	StrictMaxConcurrentRequests bool
+
 	// MaxDecoderHeaderTableSize optionally specifies an upper limit for the
 	// size of the header compression table used for decoding headers sent
 	// by the peer.