server: always use dropDRPCHeaderListener with drpc server

Previously, the DRPC listener was conditionally created based on the DRPC
setting. When DRPC was disabled, we used a noopListener that would block
on Accept() until closed, effectively rejecting all DRPC connections.

In #153503 we changed the DRPC server to always run regardless of the
setting, but missed updating the corresponding listener logic. This
commit completes that change by always using the dropDRPCHeaderListener
to properly handle incoming DRPC connections.

Epic: none
Release note: none

Author: shubhamdhama

pkg/server/start_drpc_listener.go

@@ -44,23 +44,3 @@ func (ln *dropDRPCHeaderListener) Close() error {
 func (ln *dropDRPCHeaderListener) Addr() net.Addr {
 	return ln.wrapped.Addr()
 }
-
-type noopListener struct{ done chan struct{} }
-
-func (l *noopListener) Accept() (net.Conn, error) {
-	<-l.done
-	return nil, net.ErrClosed
-}
-
-func (l *noopListener) Close() error {
-	if l.done == nil {
-		return nil
-	}
-	close(l.done)
-	l.done = nil
-	return nil
-}
-
-func (l *noopListener) Addr() net.Addr {
-	return nil
-}

pkg/server/start_listen.go

@@ -14,7 +14,6 @@ import (
 
 	"github.com/cockroachdb/cmux"
 	"github.com/cockroachdb/cockroach/pkg/rpc"
-	"github.com/cockroachdb/cockroach/pkg/rpc/rpcbase"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/netutil"
@@ -135,22 +134,10 @@ func startListenRPCAndSQL(
 		}
 	}
 
-	// Host drpc only if it's _possible_ to turn it on (this requires a test build
-	// or env var). If the setting _is_ on, then it was overridden in testing and
-	// we want to host the server too.
-	hostDRPC := rpcbase.ExperimentalDRPCEnabled.Validate(nil /* not used */, true) == nil ||
-		rpcbase.ExperimentalDRPCEnabled.Get(&cfg.Settings.SV)
-
-	// If we're not hosting drpc, make a listener that never accepts anything.
-	// We will start the dRPC server all the same; it barely consumes any
-	// resources.
-	var drpcL net.Listener = &noopListener{make(chan struct{})}
-	if hostDRPC {
-		// Throw away the header before passing the conn to the drpc server. This
-		// would not be required explicitly if we used `drpcmigrate.ListenMux` but
-		// cmux keeps the prefix.
-		drpcL = &dropDRPCHeaderListener{wrapped: m.Match(drpcMatcher)}
-	}
+	// dropDRPCHeaderListener discards the header before passing the connection
+	// to the drpc server. This would not be required if we used
+	// `drpcmigrate.ListenMux`, but cmux keeps the prefix.
+	var drpcL net.Listener = &dropDRPCHeaderListener{wrapped: m.Match(drpcMatcher)}
 
 	grpcL := m.Match(cmux.Any())
 	if serverTestKnobs, ok := cfg.TestingKnobs.Server.(*TestingKnobs); ok {