Merge pull request #110075 from luckerby/104584-retry-dial-on-socket-windows-base

Retry Unix domain sockets on Windows nodes for the plugin registration mechanism

pkg/kubelet/util/util_windows.go

@@ -29,11 +29,19 @@ import (
 	"time"
 
 	"github.com/Microsoft/go-winio"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/klog/v2"
 )
 
 const (
 	tcpProtocol   = "tcp"
 	npipeProtocol = "npipe"
+	// Amount of time to wait between attempting to use a Unix domain socket.
+	// As detailed in https://github.com/kubernetes/kubernetes/issues/104584
+	// the first attempt will most likely fail, hence the need to retry
+	socketDialRetryPeriod = 1 * time.Second
+	// Overall timeout value to dial a Unix domain socket, including retries
+	socketDialTimeout = 4 * time.Second
 )
 
 // CreateListener creates a listener on the specified endpoint.
@@ -127,6 +135,8 @@ func GetBootTime() (time.Time, error) {
 }
 
 // IsUnixDomainSocket returns whether a given file is a AF_UNIX socket file
+// Note that due to the retry logic inside, it could take up to 4 seconds
+// to determine whether or not the file path supplied is a Unix domain socket
 func IsUnixDomainSocket(filePath string) (bool, error) {
 	// Due to the absence of golang support for os.ModeSocket in Windows (https://github.com/golang/go/issues/33357)
 	// we need to dial the file and check if we receive an error to determine if a file is Unix Domain Socket file.
@@ -136,12 +146,35 @@ func IsUnixDomainSocket(filePath string) (bool, error) {
 	// does NOT work in 1809 if the socket file is created within a bind mounted directory by a container
 	// and the FSCTL is issued in the host by the kubelet.
 
-	c, err := net.Dial("unix", filePath)
-	if err == nil {
-		c.Close()
-		return true, nil
+	klog.V(6).InfoS("Function IsUnixDomainSocket starts", "filePath", filePath)
+	// As detailed in https://github.com/kubernetes/kubernetes/issues/104584 we cannot rely
+	// on the Unix Domain socket working on the very first try, hence the potential need to
+	// dial multiple times
+	var lastSocketErr error
+	err := wait.PollImmediate(socketDialRetryPeriod, socketDialTimeout,
+		func() (bool, error) {
+			klog.V(6).InfoS("Dialing the socket", "filePath", filePath)
+			var c net.Conn
+			c, lastSocketErr = net.Dial("unix", filePath)
+			if lastSocketErr == nil {
+				c.Close()
+				klog.V(6).InfoS("Socket dialed successfully", "filePath", filePath)
+				return true, nil
+			}
+			klog.V(6).InfoS("Failed the current attempt to dial the socket, so pausing before retry",
+				"filePath", filePath, "err", lastSocketErr, "socketDialRetryPeriod",
+				socketDialRetryPeriod)
+			return false, nil
+		})
+
+	// PollImmediate will return "timed out waiting for the condition" if the function it
+	// invokes never returns true
+	if err != nil {
+		klog.V(2).InfoS("Failed all attempts to dial the socket so marking it as a non-Unix Domain socket. Last socket error along with the error from PollImmediate follow",
+			"filePath", filePath, "lastSocketErr", lastSocketErr, "err", err)
+		return false, nil
 	}
-	return false, nil
+	return true, nil
 }
 
 // NormalizePath converts FS paths returned by certain go frameworks (like fsnotify)

pkg/kubelet/util/util_windows_test.go

@@ -27,6 +27,7 @@ import (
 	"os"
 	"reflect"
 	"runtime"
+	"sync"
 	"testing"
 	"time"
 
@@ -232,11 +233,50 @@ func testUnixDomainSocket(t *testing.T, label string) {
 	assert.True(t, result, "Unexpected result: false from IsUnixDomainSocket: %v for %s", result, label)
 }
 
+// This is required as on Windows it's possible for the socket file backing a Unix domain socket to
+// exist but not be ready for socket communications yet as per
+// https://github.com/kubernetes/kubernetes/issues/104584
+func testPendingUnixDomainSocket(t *testing.T, label string) {
+	// Create a temporary file that will simulate the Unix domain socket file in a
+	// not-yet-ready state. We need this because the Kubelet keeps an eye on file
+	// changes and acts on them, leading to potential race issues as described in
+	// the referenced issue above
+	f, err := ioutil.TempFile("", "test-domain-socket")
+	require.NoErrorf(t, err, "Failed to create file for test purposes: %v while setting up: %s", err, label)
+	testFile := f.Name()
+	f.Close()
+
+	// Start the check at this point
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	go func() {
+		result, err := IsUnixDomainSocket(testFile)
+		assert.Nil(t, err, "Unexpected error: %v from IsUnixDomainSocket for %s", err, label)
+		assert.True(t, result, "Unexpected result: false from IsUnixDomainSocket: %v for %s", result, label)
+		wg.Done()
+	}()
+
+	// Wait a sufficient amount of time to make sure the retry logic kicks in
+	time.Sleep(socketDialRetryPeriod)
+
+	// Replace the temporary file with an actual Unix domain socket file
+	os.Remove(testFile)
+	ta, err := net.ResolveUnixAddr("unix", testFile)
+	require.NoErrorf(t, err, "Failed to ResolveUnixAddr: %v while setting up: %s", err, label)
+	unixln, err := net.ListenUnix("unix", ta)
+	require.NoErrorf(t, err, "Failed to ListenUnix: %v while setting up: %s", err, label)
+
+	// Wait for the goroutine to finish, then close the socket
+	wg.Wait()
+	unixln.Close()
+}
+
 func TestIsUnixDomainSocket(t *testing.T) {
 	testPipe(t, "Named Pipe")
 	testRegularFile(t, "Regular File that Exists", true)
 	testRegularFile(t, "Regular File that Does Not Exist", false)
 	testUnixDomainSocket(t, "Unix Domain Socket File")
+	testPendingUnixDomainSocket(t, "Pending Unix Domain Socket File")
 }
 
 func TestNormalizePath(t *testing.T) {