From c531981886515d17516f1091916ec36fc762e73a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Knut=20Olav=20L=C3=B8ite?= <koloite@gmail.com>
Date: Thu, 11 Jun 2026 16:40:01 +0200
Subject: [PATCH 1/2] fix(examples): wait for emulator port to open before
 executing samples

---
 examples/emulator_runner.go | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/examples/emulator_runner.go b/examples/emulator_runner.go
index 59b5ce01..366d71b6 100644
--- a/examples/emulator_runner.go
+++ b/examples/emulator_runner.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"net"
 	"os"
 	"time"
 
@@ -107,19 +108,29 @@ func startEmulator() error {
 	if err := cli.ContainerStart(ctx, containerId, container.StartOptions{}); err != nil {
 		return err
 	}
-	// Wait max 10 seconds or until the emulator is running.
-	for c := 0; c < 20; c++ {
-		// Always wait at least 500 milliseconds to ensure that the emulator is actually ready, as the
-		// state can be reported as ready, while the emulator (or network interface) is actually not ready.
-		<-time.After(500 * time.Millisecond)
+	// Wait max 10 seconds or until the emulator is running and port 9010 is open.
+	var portReady bool
+	for c := 0; c < 40; c++ {
 		resp, err := cli.ContainerInspect(ctx, containerId)
 		if err != nil {
 			return fmt.Errorf("failed to inspect container state: %v", err)
 		}
 		if resp.State.Running {
-			break
+			// Try to connect to localhost:9010
+			conn, err := net.DialTimeout("tcp", "localhost:9010", 250*time.Millisecond)
+			if err == nil {
+				_ = conn.Close()
+				portReady = true
+				break
+			}
 		}
+		<-time.After(250 * time.Millisecond)
 	}
+	if !portReady {
+		return fmt.Errorf("emulator did not start listening on port 9010 in time")
+	}
+	// Give the emulator gRPC server a moment to fully initialize after the TCP port opens.
+	<-time.After(1500 * time.Millisecond)
 
 	return nil
 }

From 9f2c860fd401a5df5abb2e8b892cfaf65ed3b67d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Knut=20Olav=20L=C3=B8ite?= <koloite@gmail.com>
Date: Fri, 12 Jun 2026 18:15:53 +0200
Subject: [PATCH 2/2] chore: address review comments and add polling

---
 examples/emulator_runner.go | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/examples/emulator_runner.go b/examples/emulator_runner.go
index 366d71b6..6cc7edf5 100644
--- a/examples/emulator_runner.go
+++ b/examples/emulator_runner.go
@@ -31,6 +31,8 @@ import (
 	"github.com/docker/docker/api/types/image"
 	"github.com/docker/docker/client"
 	"github.com/docker/go-connections/nat"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 var cli *client.Client
@@ -71,7 +73,7 @@ func RunSampleOnEmulatorWithDialect(sample func(string, string, string) error, d
 
 func startEmulator() error {
 	ctx := context.Background()
-	if err := os.Setenv("SPANNER_EMULATOR_HOST", "localhost:9010"); err != nil {
+	if err := os.Setenv("SPANNER_EMULATOR_HOST", "127.0.0.1:9010"); err != nil {
 		return err
 	}
 
@@ -116,23 +118,39 @@ func startEmulator() error {
 			return fmt.Errorf("failed to inspect container state: %v", err)
 		}
 		if resp.State.Running {
-			// Try to connect to localhost:9010
-			conn, err := net.DialTimeout("tcp", "localhost:9010", 250*time.Millisecond)
+			// Try to connect to 127.0.0.1:9010
+			conn, err := net.DialTimeout("tcp", "127.0.0.1:9010", 250*time.Millisecond)
 			if err == nil {
 				_ = conn.Close()
 				portReady = true
 				break
 			}
 		}
-		<-time.After(250 * time.Millisecond)
+		time.Sleep(250 * time.Millisecond)
 	}
 	if !portReady {
 		return fmt.Errorf("emulator did not start listening on port 9010 in time")
 	}
-	// Give the emulator gRPC server a moment to fully initialize after the TCP port opens.
-	<-time.After(1500 * time.Millisecond)
+	return waitForGRPC(ctx)
+}
 
-	return nil
+func waitForGRPC(ctx context.Context) error {
+	instanceAdmin, err := instance.NewInstanceAdminClient(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to create instance admin client: %v", err)
+	}
+	defer instanceAdmin.Close()
+
+	for c := 0; c < 40; c++ {
+		_, err := instanceAdmin.GetInstance(ctx, &instancepb.GetInstanceRequest{
+			Name: "projects/p/instances/i",
+		})
+		if err == nil || status.Code(err) == codes.NotFound {
+			return nil
+		}
+		time.Sleep(100 * time.Millisecond)
+	}
+	return fmt.Errorf("emulator gRPC server did not start in time")
 }
 
 func createInstance(projectId, instanceId string) error {