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Fix broken port forwarding on K8S 1.31+ #218

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Fix broken port forwarding on K8S 1.31+ #218

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38 changes: 28 additions & 10 deletions pkg/query/portforward.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,13 @@ import (
"io/ioutil"
"net/http"
"net/url"
"os"
"time"

corev1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/labels"
"k8s.io/apimachinery/pkg/util/httpstream"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/rest"
"k8s.io/client-go/tools/portforward"
Expand All @@ -26,6 +28,9 @@ type PortForwardQuerier struct {
stopCh chan struct{}
}

// Environment variable to revert to old method of using SPDY instead of WebSockets for K8S port-forwarding
const KUBECOST_DISABLE_WEBSOCKETS = "KUBECOST_DISABLE_WEBSOCKETS"

func CreatePortForwardForService(restConfig *rest.Config, namespace, serviceName string, servicePort int, ctx context.Context) (*PortForwardQuerier, error) {
// First: find a pod to port forward to
pods, err := getServicePods(restConfig, namespace, serviceName, ctx)
Expand Down Expand Up @@ -70,17 +75,30 @@ func CreatePortForwardForService(restConfig *rest.Config, namespace, serviceName
readyCh := make(chan struct{})
stopCh := make(chan struct{}, 1)

transport, upgrader, err := spdy.RoundTripperFor(restConfig)
if err != nil {
return nil, fmt.Errorf("failed to create round tripper for rest config: %s", err)
}
mode := os.Getenv(KUBECOST_DISABLE_WEBSOCKETS)
log.Debugf("%s='%s'", KUBECOST_DISABLE_WEBSOCKETS, mode)

dialer := spdy.NewDialer(
upgrader,
&http.Client{Transport: transport},
http.MethodPost,
reqURL,
)
var dialer httpstream.Dialer
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@mittal-ishaan mittal-ishaan Oct 5, 2025

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We can do something similar to how kubectl uses it? Ref: https://github.com/kubernetes/kubectl/blob/f290e4d08347157fe2a5586127820587c058eec6/pkg/cmd/portforward/portforward.go#L139-L156
It handles few important cases like: kubernetes/kubernetes#126231

if mode != "true" {
log.Debugf("%s!=true: Use websocket mode for K8S 1.31+", KUBECOST_DISABLE_WEBSOCKETS)
dialer, err = portforward.NewSPDYOverWebsocketDialer(reqURL, restConfig)
if err != nil {
return nil, fmt.Errorf("websocket connection failure: %s", err)
}
} else {
log.Debugf("%s=true: Use SPDY mode for K8S pre-1.31", KUBECOST_DISABLE_WEBSOCKETS)

transport, upgrader, err := spdy.RoundTripperFor(restConfig)
if err != nil {
return nil, fmt.Errorf("failed to create round tripper for rest config: %s", err)
}
dialer = spdy.NewDialer(
upgrader,
&http.Client{Transport: transport},
http.MethodPost,
reqURL,
)
}

fw, err := portforward.New(
dialer,
Expand Down