perf(bigtable): use passthrough with emulator endpoint (#13739)

bhshkh · web-flow · commit dafbca228eae · 2026-01-28T09:25:30.000-08:00
Fixes #10965 This change updates the Bigtable client to use the `passthrough:///` scheme when connecting to the emulator via `BIGTABLE_EMULATOR_HOST`. This ensures consistent behavior with other Google Cloud Go clients (e.g., Spanner #10947) and avoids potential gRPC name resolution issues by forcing the passthrough resolver. It handles `BIGTABLE_EMULATOR_HOST` values with or without an existing scheme (e.g. `localhost:9000` or `http://localhost:9000`).
diff --git a/bigtable/internal/option/option.go b/bigtable/internal/option/option.go
@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -49,6 +50,8 @@ const (
 	BigtableConnectionPoolEnvVar = "CBT_BIGTABLE_CONN_POOL"
 )
 
+var schemeRegexp = regexp.MustCompile("^(http://|https://|passthrough:///)")
+
 // mergeOutgoingMetadata returns a context populated by the existing outgoing
 // metadata merged with the provided mds.
 func mergeOutgoingMetadata(ctx context.Context, mds ...metadata.MD) context.Context {
@@ -108,7 +111,8 @@ func DefaultClientOptions(endpoint, mtlsEndpoint, scope, userAgent string) ([]op
 	// Check the environment variables for the bigtable emulator.
 	// Dial it directly and don't pass any credentials.
 	if addr := os.Getenv("BIGTABLE_EMULATOR_HOST"); addr != "" {
-		conn, err := grpc.Dial(addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+		schemeRemoved := schemeRegexp.ReplaceAllString(addr, "")
+		conn, err := grpc.Dial("passthrough:///"+schemeRemoved, grpc.WithTransportCredentials(insecure.NewCredentials()))
 		if err != nil {
 			return nil, fmt.Errorf("emulator grpc.Dial: %w", err)
 		}
