Add debug log level support to VirtualMCPServer

Adds LogLevel field to VirtualMCPServer CRD OperationalConfig to allow
enabling debug logging for vMCP instances. The field accepts only 'debug'
as a valid value. When not set, the vmcp binary defaults to info level.

The deployment builder passes the --debug flag to the vmcp container when
LogLevel is set to 'debug'. This is the only log level flag supported by
the vmcp binary, as the logger initializes before the config file is loaded.

Bumps CRD chart version from 0.0.74 to 0.0.75.

Fixes #2781

Signed-off-by: 4t8dd <wanger.xyz@gmail.com>

Author: 4t8dd

cmd/thv-operator/api/v1alpha1/virtualmcpserver_types.go

@@ -330,6 +330,12 @@ type ErrorHandling struct {
 
 // OperationalConfig defines operational settings
 type OperationalConfig struct {
+	// LogLevel sets the logging level for the Virtual MCP server.
+	// Set to "debug" to enable debug logging. When not set, defaults to info level.
+	// +kubebuilder:validation:Enum=debug
+	// +optional
+	LogLevel string `json:"logLevel,omitempty"`
+
 	// Timeouts configures timeout settings
 	// +optional
 	Timeouts *TimeoutConfig `json:"timeouts,omitempty"`

cmd/thv-operator/controllers/virtualmcpserver_deployment.go

@@ -71,7 +71,7 @@ func (r *VirtualMCPServerReconciler) deploymentForVirtualMCPServer(
 	replicas := int32(1)
 
 	// Build deployment components using helper functions
-	args := r.buildContainerArgsForVmcp()
+	args := r.buildContainerArgsForVmcp(vmcp)
 	volumeMounts, volumes := r.buildVolumesForVmcp(vmcp)
 	env := r.buildEnvVarsForVmcp(ctx, vmcp, workloadNames)
 	deploymentLabels, deploymentAnnotations := r.buildDeploymentMetadataForVmcp(ls, vmcp)
@@ -141,13 +141,24 @@ func (r *VirtualMCPServerReconciler) deploymentForVirtualMCPServer(
 }
 
 // buildContainerArgsForVmcp builds the container arguments for vmcp
-func (*VirtualMCPServerReconciler) buildContainerArgsForVmcp() []string {
-	return []string{
+func (*VirtualMCPServerReconciler) buildContainerArgsForVmcp(
+	vmcp *mcpv1alpha1.VirtualMCPServer,
+) []string {
+	args := []string{
 		"serve",
 		"--config=/etc/vmcp-config/config.yaml",
 		"--host=0.0.0.0", // Listen on all interfaces for Kubernetes service routing
 		"--port=4483",    // Standard vmcp port
 	}
+
+	// Add --debug flag if log level is set to debug
+	// Note: vmcp binary currently only supports --debug flag, not other log levels
+	// The flag must be passed at startup because logger.Initialize() runs before config is loaded
+	if vmcp.Spec.Operational != nil && vmcp.Spec.Operational.LogLevel == "debug" {
+		args = append(args, "--debug")
+	}
+
+	return args
 }
 
 // buildVolumesForVmcp builds volumes and volume mounts for vmcp

cmd/thv-operator/controllers/virtualmcpserver_deployment_test.go

@@ -79,11 +79,56 @@ func TestDeploymentForVirtualMCPServer(t *testing.T) {
 func TestBuildContainerArgsForVmcp(t *testing.T) {
 	t.Parallel()
 
-	r := &VirtualMCPServerReconciler{}
-	args := r.buildContainerArgsForVmcp()
+	tests := []struct {
+		name     string
+		vmcp     *mcpv1alpha1.VirtualMCPServer
+		wantArgs []string
+	}{
+		{
+			name: "without log level",
+			vmcp: &mcpv1alpha1.VirtualMCPServer{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "test-vmcp",
+					Namespace: "default",
+				},
+				Spec: mcpv1alpha1.VirtualMCPServerSpec{
+					GroupRef: mcpv1alpha1.GroupRef{
+						Name: "test-group",
+					},
+				},
+			},
+			wantArgs: []string{"serve", "--config=/etc/vmcp-config/config.yaml", "--host=0.0.0.0", "--port=4483"},
+		},
+		{
+			name: "with log level debug",
+			vmcp: &mcpv1alpha1.VirtualMCPServer{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "test-vmcp",
+					Namespace: "default",
+				},
+				Spec: mcpv1alpha1.VirtualMCPServerSpec{
+					GroupRef: mcpv1alpha1.GroupRef{
+						Name: "test-group",
+					},
+					Operational: &mcpv1alpha1.OperationalConfig{
+						LogLevel: "debug",
+					},
+				},
+			},
+			wantArgs: []string{"serve", "--config=/etc/vmcp-config/config.yaml", "--host=0.0.0.0", "--port=4483", "--debug"},
+		},
+	}
 
-	assert.Contains(t, args, "serve")
-	assert.Contains(t, args, "--config=/etc/vmcp-config/config.yaml")
+	for _, tt := range tests {
+		tt := tt // capture range variable
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			r := &VirtualMCPServerReconciler{}
+			args := r.buildContainerArgsForVmcp(tt.vmcp)
+
+			assert.Equal(t, tt.wantArgs, args)
+		})
+	}
 }
 
 // TestBuildVolumesForVmcp tests volume and volume mount generation

deploy/charts/operator-crds/Chart.yaml

@@ -2,5 +2,5 @@ apiVersion: v2
 name: toolhive-operator-crds
 description: A Helm chart for installing the ToolHive Operator CRDs into Kubernetes.
 type: application
-version: 0.0.74
+version: 0.0.75
 appVersion: "0.0.1"

deploy/charts/operator-crds/README.md

@@ -1,6 +1,6 @@
 # ToolHive Operator CRDs Helm Chart
 
-![Version: 0.0.74](https://img.shields.io/badge/Version-0.0.74-informational?style=flat-square)
+![Version: 0.0.75](https://img.shields.io/badge/Version-0.0.75-informational?style=flat-square)
 ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square)
 
 A Helm chart for installing the ToolHive Operator CRDs into Kubernetes.

deploy/charts/operator-crds/crds/toolhive.stacklok.dev_virtualmcpservers.yaml

@@ -624,6 +624,13 @@ spec:
                           failures before marking unhealthy
                         type: integer
                     type: object
+                  logLevel:
+                    description: |-
+                      LogLevel sets the logging level for the Virtual MCP server.
+                      Set to "debug" to enable debug logging. When not set, defaults to info level.
+                    enum:
+                    - debug
+                    type: string
                   timeouts:
                     description: Timeouts configures timeout settings
                     properties: