e2e: add port-forwarding utility

e2e/internal/kubeclient/portforward.go

@@ -0,0 +1,74 @@
+package kubeclient
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"k8s.io/client-go/tools/portforward"
+	"k8s.io/client-go/transport/spdy"
+)
+
+// PortForwardPod starts a port forward to the selected pod.
+//
+// On success, the function returns a TCP address that clients can connect to and a function to
+// cancel the port forwarding.
+func (k *Kubeclient) PortForwardPod(ctx context.Context, namespace, podName, remotePort string) (string, func(), error) {
+	// This channel sends a stop request to the portforwarding goroutine.
+	stopCh := make(chan struct{}, 1)
+	// The portforwarding goroutine closes this channel when it's ready.
+	readyCh := make(chan struct{})
+	// Any error returned by the background port-forwarder is sent to this channel.
+	errorCh := make(chan error)
+
+	// Ports are forwarded by upgrading this POST request to a SPDY connection.
+	req := k.client.CoreV1().RESTClient().Post().
+		Resource("pods").
+		Namespace(namespace).
+		Name(podName).
+		SubResource("portforward")
+
+	transport, upgrader, err := spdy.RoundTripperFor(k.config)
+	if err != nil {
+		return "", nil, fmt.Errorf("creating round tripper: %w", err)
+	}
+
+	dialer := spdy.NewDialer(upgrader, &http.Client{Transport: transport}, http.MethodPost, req.URL())
+
+	fw, err := portforward.NewOnAddresses(
+		dialer,
+		[]string{"localhost"},
+		[]string{fmt.Sprintf("0:%s", remotePort)},
+		stopCh, readyCh,
+		nil, nil,
+	)
+	if err != nil {
+		return "", nil, fmt.Errorf("creating portforwarder: %w", err)
+	}
+
+	go func() {
+		if err := fw.ForwardPorts(); err != nil {
+			errorCh <- err
+		}
+	}()
+
+	select {
+	case <-readyCh:
+		ports, err := fw.GetPorts()
+		if err != nil {
+			close(stopCh)
+			return "", nil, fmt.Errorf("getting ports: %w", err)
+		}
+		cleanUp := func() {
+			close(stopCh)
+		}
+		return fmt.Sprintf("localhost:%d", ports[0].Local), cleanUp, nil
+
+	case <-ctx.Done():
+		close(stopCh)
+		return "", nil, fmt.Errorf("waiting for port forward to be ready: %w", ctx.Err())
+	case err := <-errorCh:
+		close(stopCh)
+		return "", nil, fmt.Errorf("background port-forwarding routine failed: %w", err)
+	}
+}