test: consolidate port allocation into shared test/testutil package (#8982)

* test: consolidate port allocation into shared test/testutil package

Move duplicated port allocation logic from 15+ test files into a single
shared package at test/testutil/. This fixes a port collision bug where
independently allocated ports could overlap via the gRPC offset
(port+10000), causing weed mini to reject the configuration.

The shared package provides:
- AllocatePorts: atomic allocation of N unique ports
- AllocateMiniPorts/MustFreeMiniPorts: gRPC-offset-aware allocation
  that prevents port A+10000 == port B collisions
- WaitForPort, WaitForService, FindBindIP, WriteIAMConfig, HasDocker

* test: address review feedback and fix FUSE build

- Revert fuse_integration change: it has its own go.mod and cannot
  import the shared testutil package
- AllocateMiniPorts: hold all listeners open until the entire batch is
  allocated, preventing race conditions where other processes steal ports
- HasDocker: add 5s context timeout to avoid hanging on stalled Docker
- WaitForService: only treat 2xx HTTP status codes as ready

* test: use global rand in AllocateMiniPorts for better seeding

Go 1.20+ auto-seeds the global rand generator. Using it avoids
identical sequences when multiple tests call at the same nanosecond.

* test: revert WaitForService status code check

S3 endpoints return non-2xx (e.g. 403) on bare GET requests, so
requiring 2xx caused the S3 integration test to time out. Any HTTP
response is sufficient proof that the service is running.

* test: fix gofmt formatting in s3tables test files

test/s3/normal/s3_integration_test.go

@@ -7,7 +7,6 @@ import (
 	"encoding/base64"
 	"fmt"
 	"math/rand"
-	"net"
 	"net/http"
 	"os"
 	"os/exec"
@@ -25,6 +24,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/seaweedfs/seaweedfs/test/testutil"
 	"github.com/seaweedfs/seaweedfs/test/volume_server/framework"
 	"github.com/seaweedfs/seaweedfs/weed/command"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
@@ -112,37 +112,16 @@ func TestS3Integration(t *testing.T) {
 }
 
 // findAvailablePort finds an available port by binding to port 0
-func findAvailablePort() (int, error) {
-	listener, err := net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
-		return 0, err
-	}
-	defer listener.Close()
-
-	addr := listener.Addr().(*net.TCPAddr)
-	return addr.Port, nil
-}
 
 // startMiniCluster starts a weed mini instance directly without exec.
 // Extra flags (e.g. "-s3.allowDeleteBucketNotEmpty=false") can be appended via extraArgs.
 func startMiniCluster(t *testing.T, extraArgs ...string) (*TestCluster, error) {
-	// Find available ports
-	masterPort, err := findAvailablePort()
-	if err != nil {
-		return nil, fmt.Errorf("failed to find master port: %v", err)
-	}
-	volumePort, err := findAvailablePort()
-	if err != nil {
-		return nil, fmt.Errorf("failed to find volume port: %v", err)
-	}
-	filerPort, err := findAvailablePort()
-	if err != nil {
-		return nil, fmt.Errorf("failed to find filer port: %v", err)
-	}
-	s3Port, err := findAvailablePort()
-	if err != nil {
-		return nil, fmt.Errorf("failed to find s3 port: %v", err)
-	}
+	// Allocate non-colliding ports (including gRPC offsets) for weed mini.
+	ports := testutil.MustFreeMiniPorts(t, []string{"Master", "Volume", "Filer", "S3"})
+	masterPort := ports[0]
+	volumePort := ports[1]
+	filerPort := ports[2]
+	s3Port := ports[3]
 	// Create temporary directory for test data
 	testDir := t.TempDir()
 
@@ -167,7 +146,7 @@ func startMiniCluster(t *testing.T, extraArgs ...string) (*TestCluster, error) {
 
 	// Create empty security.toml to disable JWT authentication in tests
 	securityToml := filepath.Join(testDir, "security.toml")
-	err = os.WriteFile(securityToml, []byte("# Empty security config for testing\n"), 0644)
+	err := os.WriteFile(securityToml, []byte("# Empty security config for testing\n"), 0644)
 	if err != nil {
 		cancel()
 		return nil, fmt.Errorf("failed to create security.toml: %v", err)
@@ -233,10 +212,9 @@ func startMiniCluster(t *testing.T, extraArgs ...string) (*TestCluster, error) {
 	}()
 
 	// Wait for S3 service to be ready
-	err = waitForS3Ready(cluster.s3Endpoint, 30*time.Second)
-	if err != nil {
+	if !testutil.WaitForService(cluster.s3Endpoint, 30*time.Second) {
 		cancel()
-		return nil, fmt.Errorf("S3 service failed to start: %v", err)
+		return nil, fmt.Errorf("S3 service failed to start at %s", cluster.s3Endpoint)
 	}
 
 	// If VOLUME_SERVER_IMPL=rust, start a Rust volume server alongside weed mini
@@ -277,14 +255,12 @@ func (c *TestCluster) startRustVolumeServer(t *testing.T) error {
 		return fmt.Errorf("resolve rust volume binary: %v", err)
 	}
 
-	rustVolumePort, err := findAvailablePort()
+	rustPorts, err := testutil.AllocatePorts(2)
 	if err != nil {
-		return fmt.Errorf("find rust volume port: %v", err)
-	}
-	rustVolumeGrpcPort, err := findAvailablePort()
-	if err != nil {
-		return fmt.Errorf("find rust volume grpc port: %v", err)
+		return fmt.Errorf("find rust volume ports: %v", err)
 	}
+	rustVolumePort := rustPorts[0]
+	rustVolumeGrpcPort := rustPorts[1]
 
 	rustVolumeDir := filepath.Join(c.dataDir, "rust-volume")
 	if err := os.MkdirAll(rustVolumeDir, 0o755); err != nil {
@@ -377,25 +353,6 @@ func (c *TestCluster) Stop() {
 	}
 }
 
-// waitForS3Ready waits for the S3 service to be ready
-func waitForS3Ready(endpoint string, timeout time.Duration) error {
-	client := &http.Client{Timeout: 1 * time.Second}
-	deadline := time.Now().Add(timeout)
-
-	for time.Now().Before(deadline) {
-		resp, err := client.Get(endpoint)
-		if err == nil {
-			resp.Body.Close()
-			// Wait a bit more to ensure service is fully ready
-			time.Sleep(500 * time.Millisecond)
-			return nil
-		}
-		time.Sleep(200 * time.Millisecond)
-	}
-
-	return fmt.Errorf("timeout waiting for S3 service at %s", endpoint)
-}
-
 // Test functions
 
 func testCreateBucket(t *testing.T, cluster *TestCluster) {