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feat: an inbuilt gateway to handle kubectl host proxying (#91)
this is useful in a few places 1. you can't run minikube tunnel -> say you are using a remote cluster 2. you are on codespaces and you can't run minikube tunnel
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,164 @@ | ||
| package deployment | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "io" | ||
| "k8s.io/client-go/kubernetes" | ||
| "k8s.io/client-go/rest" | ||
| "log" | ||
| "net/http" | ||
| "net/http/httputil" | ||
| "net/url" | ||
| "os" | ||
| "os/signal" | ||
| "strings" | ||
| "syscall" | ||
| "time" | ||
|
|
||
| metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" | ||
| "k8s.io/client-go/tools/portforward" | ||
| "k8s.io/client-go/transport/spdy" | ||
| ) | ||
|
|
||
| const ( | ||
| namespace = "istio-system" | ||
| service = "istio-ingressgateway" | ||
| localPortForIstio = 9080 | ||
| istioGatewayPodPort = 8080 | ||
| proxyServerPort = 9060 | ||
| ) | ||
|
|
||
| func StartGateway(host string) error { | ||
| log.Printf("Starting gateway for host: %s", host) | ||
|
|
||
| client, err := createKubernetesClient() | ||
| if err != nil { | ||
| return fmt.Errorf("an error occurred while creating a kubernetes client:\n %v", err) | ||
| } | ||
|
|
||
| // Find a pod for the service | ||
| pod, err := findPodForService(client.clientSet) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to find pod for service: %v", err) | ||
| } | ||
|
|
||
| // Start port forwarding | ||
| stopChan := make(chan struct{}, 1) | ||
| readyChan := make(chan struct{}) | ||
| go func() { | ||
| for { | ||
| err := portForwardPod(client.config, pod, stopChan, readyChan) | ||
| if err != nil { | ||
| log.Printf("Port forwarding failed: %v. Retrying in 5 seconds...", err) | ||
| time.Sleep(5 * time.Second) | ||
| continue | ||
| } | ||
| break | ||
| } | ||
| }() | ||
|
|
||
| // Wait for port forwarding to be ready | ||
| <-readyChan | ||
|
|
||
| // Start proxy server | ||
| proxy := createProxy(host) | ||
| server := &http.Server{ | ||
| Addr: fmt.Sprintf(":%d", proxyServerPort), | ||
| Handler: proxy, | ||
| } | ||
|
|
||
| go func() { | ||
| if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed { | ||
| log.Fatalf("Failed to start proxy server: %v", err) | ||
| } | ||
| }() | ||
|
|
||
| log.Printf("Proxy server for host %s started on http://localhost:%d", host, proxyServerPort) | ||
|
|
||
| sigChan := make(chan os.Signal, 1) | ||
| signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM) | ||
| <-sigChan | ||
|
|
||
| log.Println("Shutting down...") | ||
| close(stopChan) | ||
| ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second) | ||
| defer cancel() | ||
| if err := server.Shutdown(ctx); err != nil { | ||
| log.Printf("Server shutdown error: %v", err) | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| func findPodForService(client *kubernetes.Clientset) (string, error) { | ||
| svc, err := client.CoreV1().Services(namespace).Get(context.Background(), service, metav1.GetOptions{}) | ||
| if err != nil { | ||
| return "", fmt.Errorf("error getting service: %v", err) | ||
| } | ||
|
|
||
| var labelSelectors []string | ||
| for key, value := range svc.Spec.Selector { | ||
| labelSelectors = append(labelSelectors, fmt.Sprintf("%s=%s", key, value)) | ||
| } | ||
| selector := strings.Join(labelSelectors, ",") | ||
|
|
||
| pods, err := client.CoreV1().Pods(namespace).List(context.Background(), metav1.ListOptions{LabelSelector: selector}) | ||
| if err != nil { | ||
| return "", fmt.Errorf("error listing pods: %v", err) | ||
| } | ||
|
|
||
| if len(pods.Items) == 0 { | ||
| return "", fmt.Errorf("no pods found for service %s", service) | ||
| } | ||
|
|
||
| podName := pods.Items[0].Name | ||
| return podName, nil | ||
| } | ||
|
|
||
| func portForwardPod(config *rest.Config, podName string, stopChan <-chan struct{}, readyChan chan struct{}) error { | ||
| roundTripper, upgrader, err := spdy.RoundTripperFor(config) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to create round tripper: %v", err) | ||
| } | ||
|
|
||
| path := fmt.Sprintf("/api/v1/namespaces/%s/pods/%s/portforward", namespace, podName) | ||
| hostIP := strings.TrimLeft(config.Host, "htps:/") | ||
|
|
||
| serverURL, err := url.Parse(fmt.Sprintf("https://%s%s", hostIP, path)) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to parse URL: %v", err) | ||
| } | ||
|
|
||
| dialer := spdy.NewDialer(upgrader, &http.Client{Transport: roundTripper}, http.MethodPost, serverURL) | ||
|
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| ports := []string{fmt.Sprintf("%d:%d", localPortForIstio, istioGatewayPodPort)} | ||
| forwarder, err := portforward.New(dialer, ports, stopChan, readyChan, io.Discard, os.Stderr) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to create port forwarder: %v", err) | ||
| } | ||
|
|
||
| return forwarder.ForwardPorts() | ||
| } | ||
|
|
||
| func createProxy(host string) *httputil.ReverseProxy { | ||
| target, _ := url.Parse(fmt.Sprintf("http://localhost:%d", localPortForIstio)) | ||
| proxy := httputil.NewSingleHostReverseProxy(target) | ||
|
|
||
| originalDirector := proxy.Director | ||
| proxy.Director = func(req *http.Request) { | ||
| originalDirector(req) | ||
| req.Host = host // Set the Host header to the provided host | ||
| req.Header.Set("X-Forwarded-Host", host) | ||
| } | ||
|
|
||
| proxy.ModifyResponse = func(resp *http.Response) error { | ||
| // Set cache-control headers | ||
| resp.Header.Set("Cache-Control", "no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0") | ||
| resp.Header.Set("Pragma", "no-cache") | ||
| resp.Header.Set("Expires", "0") | ||
| return nil | ||
| } | ||
|
|
||
| return proxy | ||
| } |
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