feat: watch for configuration changes

Watch kube config files for changes.
Automatically reload kubernetes client and list of tools.

Useful for logins or context changes after an MCP session has started.

pkg/kubernetes/kubernetes.go

@@ -1,6 +1,7 @@
 package kubernetes
 
 import (
+	"github.com/fsnotify/fsnotify"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/discovery/cached/memory"
@@ -17,8 +18,12 @@ import (
 // Exposed for testing
 var InClusterConfig = rest.InClusterConfig
 
+type CloseWatchKubeConfig func() error
+
 type Kubernetes struct {
 	cfg                         *rest.Config
+	kubeConfigFiles             []string
+	CloseWatchKubeConfig        CloseWatchKubeConfig
 	clientSet                   *kubernetes.Clientset
 	discoveryClient             *discovery.DiscoveryClient
 	deferredDiscoveryRESTMapper *restmapper.DeferredDiscoveryRESTMapper
@@ -44,6 +49,7 @@ func NewKubernetes() (*Kubernetes, error) {
 	}
 	return &Kubernetes{
 		cfg:                         cfg,
+		kubeConfigFiles:             resolveConfig().ConfigAccess().GetLoadingPrecedence(),
 		clientSet:                   clientSet,
 		discoveryClient:             discoveryClient,
 		deferredDiscoveryRESTMapper: restmapper.NewDeferredDiscoveryRESTMapper(memory.NewMemCacheClient(discoveryClient)),
@@ -51,6 +57,44 @@ func NewKubernetes() (*Kubernetes, error) {
 	}, nil
 }
 
+func (k *Kubernetes) WatchKubeConfig(onKubeConfigChange func() error) {
+	if len(k.kubeConfigFiles) == 0 {
+		return
+	}
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return
+	}
+	for _, file := range k.kubeConfigFiles {
+		_ = watcher.Add(file)
+	}
+	go func() {
+		for {
+			select {
+			case _, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
+				_ = onKubeConfigChange()
+			case _, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
+			}
+		}
+	}()
+	if k.CloseWatchKubeConfig != nil {
+		_ = k.CloseWatchKubeConfig()
+	}
+	k.CloseWatchKubeConfig = watcher.Close
+}
+
+func (k *Kubernetes) Close() {
+	if k.CloseWatchKubeConfig != nil {
+		_ = k.CloseWatchKubeConfig()
+	}
+}
+
 func marshal(v any) (string, error) {
 	switch t := v.(type) {
 	case []unstructured.Unstructured: