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.

Author: manusa

README.md

@@ -13,8 +13,9 @@ https://github.com/user-attachments/assets/be2b67b3-fc1c-4d11-ae46-93deba8ed98e
 
 A powerful and flexible Kubernetes [Model Context Protocol (MCP)](https://blog.marcnuri.com/model-context-protocol-mcp-introduction) server implementation with support for OpenShift.
 
-- **✅ Configuration**: View and manage the [Kubernetes `.kube/config`](https://blog.marcnuri.com/where-is-my-default-kubeconfig-file).
-  - **View** the current configuration.
+- **✅ Configuration**:
+  - Automatically detect changes in the Kubernetes configuration and update the MCP server.
+  - **View** and manage the current [Kubernetes `.kube/config`](https://blog.marcnuri.com/where-is-my-default-kubeconfig-file) or in-cluster configuration.
 - **✅ Generic Kubernetes Resources**: Perform operations on any Kubernetes resource.
   - Any CRUD operation (Create or Update, Get, List, Delete).
 - **✅ Pods**: Perform Pod-specific operations.

go.mod

@@ -3,6 +3,7 @@ module github.com/manusa/kubernetes-mcp-server
 go 1.23.5
 
 require (
+	github.com/fsnotify/fsnotify v1.8.0
 	github.com/mark3labs/mcp-go v0.15.0
 	github.com/spf13/afero v1.14.0
 	github.com/spf13/cobra v1.9.1
@@ -22,7 +23,6 @@ require (
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/emicklei/go-restful/v3 v3.11.0 // indirect
 	github.com/evanphx/json-patch/v5 v5.9.11 // indirect
-	github.com/fsnotify/fsnotify v1.8.0 // indirect
 	github.com/fxamacker/cbor/v2 v2.7.0 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-openapi/jsonpointer v0.21.0 // indirect

pkg/kubernetes-mcp-server/cmd/root.go

@@ -42,20 +42,19 @@ Kubernetes Model Context Protocol (MCP) server
 		if err != nil {
 			panic(err)
 		}
+		defer mcpServer.Close()
 
 		var sseServer *server.SSEServer
 		if ssePort := viper.GetInt("sse-port"); ssePort > 0 {
 			sseServer = mcpServer.ServeSse(viper.GetString("sse-base-url"))
 			if err := sseServer.Start(fmt.Sprintf(":%d", ssePort)); err != nil {
 				panic(err)
 			}
+			defer sseServer.Shutdown(cmd.Context())
 		}
 		if err := mcpServer.ServeStdio(); err != nil && !errors.Is(err, context.Canceled) {
 			panic(err)
 		}
-		if sseServer != nil {
-			_ = sseServer.Shutdown(cmd.Context())
-		}
 	},
 }
 

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
@@ -44,13 +49,52 @@ func NewKubernetes() (*Kubernetes, error) {
 	}
 	return &Kubernetes{
 		cfg:                         cfg,
+		kubeConfigFiles:             resolveConfig().ConfigAccess().GetLoadingPrecedence(),
 		clientSet:                   clientSet,
 		discoveryClient:             discoveryClient,
 		deferredDiscoveryRESTMapper: restmapper.NewDeferredDiscoveryRESTMapper(memory.NewMemCacheClient(discoveryClient)),
 		dynamicClient:               dynamicClient,
 	}, 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:

pkg/mcp/common_test.go

@@ -129,6 +129,7 @@ func (c *mcpContext) beforeEach(t *testing.T) {
 
 func (c *mcpContext) afterEach() {
 	c.cancel()
+	c.mcpServer.Close()
 	_ = c.mcpClient.Close()
 	c.mcpHttpServer.Close()
 }

pkg/mcp/mcp.go

@@ -27,6 +27,7 @@ func NewSever() (*Server, error) {
 	if err := s.reloadKubernetesClient(); err != nil {
 		return nil, err
 	}
+	s.k.WatchKubeConfig(s.reloadKubernetesClient)
 	return s, nil
 }
 
@@ -57,6 +58,12 @@ func (s *Server) ServeSse(baseUrl string) *server.SSEServer {
 	return server.NewSSEServer(s.server, options...)
 }
 
+func (s *Server) Close() {
+	if s.k != nil {
+		s.k.Close()
+	}
+}
+
 func NewTextResult(content string, err error) *mcp.CallToolResult {
 	if err != nil {
 		return &mcp.CallToolResult{

pkg/mcp/mcp_test.go

@@ -1,12 +1,51 @@
 package mcp
 
 import (
+	"context"
 	"github.com/mark3labs/mcp-go/mcp"
+	"os"
+	"path/filepath"
 	"slices"
 	"strings"
 	"testing"
+	"time"
 )
 
+func TestWatchKubeConfig(t *testing.T) {
+	testCase(t, func(c *mcpContext) {
+		// Given
+		withTimeout, cancel := context.WithTimeout(c.ctx, 5*time.Second)
+		defer cancel()
+		var notification *mcp.JSONRPCNotification
+		c.mcpClient.OnNotification(func(n mcp.JSONRPCNotification) {
+			notification = &n
+		})
+		// When
+		f, _ := os.OpenFile(filepath.Join(c.tempDir, "config"), os.O_APPEND|os.O_WRONLY, 0644)
+		_, _ = f.WriteString("\n")
+		for {
+			if notification != nil {
+				break
+			}
+			select {
+			case <-withTimeout.Done():
+				break
+			default:
+				time.Sleep(100 * time.Millisecond)
+			}
+		}
+		// Then
+		t.Run("WatchKubeConfig notifies tools change", func(t *testing.T) {
+			if notification == nil {
+				t.Fatalf("WatchKubeConfig did not notify")
+			}
+			if notification.Method != "notifications/tools/list_changed" {
+				t.Fatalf("WatchKubeConfig did not notify tools change, got %s", notification.Method)
+			}
+		})
+	})
+}
+
 func TestTools(t *testing.T) {
 	expectedNames := []string{
 		"configuration_view",