fix(transport): remove conditional App Engine gen 1 Go hooks (#2158)

* Remove gRPC hook for google.golang.org/appengine/socket
* Remove HTTP hook for google.golang.org/appengine/urlfetch

Both hooks load packages that are no longer intended for use in the App Engine Go second generation runtime (>= Go 1.11).

closes: #2128

go.mod

@@ -13,7 +13,6 @@ require (
 	golang.org/x/net v0.15.0
 	golang.org/x/oauth2 v0.12.0
 	golang.org/x/sync v0.3.0
-	google.golang.org/appengine v1.6.7
 	google.golang.org/genproto/googleapis/bytestream v0.0.0-20230911183012-2d3300fd4832
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20230911183012-2d3300fd4832
 	google.golang.org/grpc v1.57.0
@@ -27,6 +26,7 @@ require (
 	golang.org/x/crypto v0.13.0 // indirect
 	golang.org/x/sys v0.12.0 // indirect
 	golang.org/x/text v0.13.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20230803162519-f966b187b2e5 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20230803162519-f966b187b2e5 // indirect
 )

transport/grpc/dial.go

@@ -35,9 +35,6 @@ const disableDirectPath = "GOOGLE_CLOUD_DISABLE_DIRECT_PATH"
 // Check env to decide if using google-c2p resolver for DirectPath traffic.
 const enableDirectPathXds = "GOOGLE_CLOUD_ENABLE_DIRECT_PATH_XDS"
 
-// Set at init time by dial_appengine.go. If nil, we're not on App Engine.
-var appengineDialerHook func(context.Context) grpc.DialOption
-
 // Set at init time by dial_socketopt.go. If nil, socketopt is not supported.
 var timeoutDialerOption grpc.DialOption
 
@@ -186,12 +183,6 @@ func dial(ctx context.Context, insecure bool, o *internal.DialSettings) (*grpc.C
 		}
 	}
 
-	if appengineDialerHook != nil {
-		// Use the Socket API on App Engine.
-		// appengine dialer will override socketopt dialer
-		grpcOpts = append(grpcOpts, appengineDialerHook(ctx))
-	}
-
 	// Add tracing, but before the other options, so that clients can override the
 	// gRPC stats handler.
 	// This assumes that gRPC options are processed in order, left to right.

transport/grpc/dial_test.go

@@ -5,55 +5,9 @@
 package grpc
 
 import (
-	"context"
-	"errors"
-	"net"
 	"testing"
-	"time"
-
-	"golang.org/x/oauth2"
-	"google.golang.org/api/option"
-	"google.golang.org/grpc"
 )
 
-// Check that user optioned grpc.WithDialer option overwrites App Engine dialer
-func TestGRPCHook(t *testing.T) {
-	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
-	expected := false
-
-	appengineDialerHook = (func(ctx context.Context) grpc.DialOption {
-		return grpc.WithDialer(func(addr string, timeout time.Duration) (net.Conn, error) {
-			t.Error("did not expect a call to appengine dialer, got one")
-			cancel()
-			return nil, errors.New("not expected")
-		})
-	})
-	defer func() {
-		appengineDialerHook = nil
-	}()
-
-	expectedDialer := grpc.WithDialer(func(addr string, timeout time.Duration) (net.Conn, error) {
-		expected = true
-		cancel()
-		return nil, errors.New("expected")
-	})
-
-	conn, err := Dial(ctx,
-		option.WithTokenSource(oauth2.StaticTokenSource(nil)), // No creds.
-		option.WithGRPCDialOption(expectedDialer),
-		option.WithGRPCDialOption(grpc.WithBlock()))
-	if err != context.Canceled {
-		t.Errorf("got %v, want %v", err, context.Canceled)
-	}
-	if conn != nil {
-		conn.Close()
-		t.Error("got valid conn, want nil")
-	}
-	if !expected {
-		t.Error("expected a call to expected dialer, didn't get one")
-	}
-}
-
 func TestCheckDirectPathEndPoint(t *testing.T) {
 	for _, testcase := range []struct {
 		name     string

transport/http/dial.go

@@ -145,22 +145,13 @@ func (t *parameterTransport) RoundTrip(req *http.Request) (*http.Response, error
 	return rt.RoundTrip(&newReq)
 }
 
-// Set at init time by dial_appengine.go. If nil, we're not on App Engine.
-var appengineUrlfetchHook func(context.Context) http.RoundTripper
-
-// defaultBaseTransport returns the base HTTP transport.
-// On App Engine, this is urlfetch.Transport.
-// Otherwise, use a default transport, taking most defaults from
-// http.DefaultTransport.
+// defaultBaseTransport returns the base HTTP transport. It uses a default
+// transport, taking most defaults from http.DefaultTransport.
 // If TLSCertificate is available, set TLSClientConfig as well.
 func defaultBaseTransport(ctx context.Context, clientCertSource cert.Source, dialTLSContext func(context.Context, string, string) (net.Conn, error)) http.RoundTripper {
-	if appengineUrlfetchHook != nil {
-		return appengineUrlfetchHook(ctx)
-	}
-
 	// Copy http.DefaultTransport except for MaxIdleConnsPerHost setting,
-	// which is increased due to reported performance issues under load in the GCS
-	// client. Transport.Clone is only available in Go 1.13 and up.
+	// which is increased due to reported performance issues under load in the
+	// GCS client. Transport.Clone is only available in Go 1.13 and up.
 	trans := clonedTransport(http.DefaultTransport)
 	if trans == nil {
 		trans = fallbackBaseTransport()