Implement capability discovery and querying for Virtual MCP Server

pkg/vmcp/aggregator/aggregator.go

@@ -29,17 +29,34 @@ type BackendDiscoverer interface {
 //  1. Query: Fetch capabilities from each backend
 //  2. Conflict Resolution: Handle duplicate tool/resource/prompt names
 //  3. Merging: Create final unified capability view and routing table
+//
+//go:generate mockgen -destination=mocks/mock_interfaces.go -package=mocks -source=aggregator.go BackendDiscoverer Aggregator ConflictResolver ToolFilter ToolOverride
 type Aggregator interface {
 	// QueryCapabilities queries a backend for its MCP capabilities.
 	// Returns the raw capabilities (tools, resources, prompts) from the backend.
 	QueryCapabilities(ctx context.Context, backend vmcp.Backend) (*BackendCapabilities, error)
 
+	// QueryAllCapabilities queries all backends for their capabilities in parallel.
+	// Handles backend failures gracefully (logs and continues with remaining backends).
+	QueryAllCapabilities(ctx context.Context, backends []vmcp.Backend) (map[string]*BackendCapabilities, error)
+
 	// ResolveConflicts applies conflict resolution strategy to handle
 	// duplicate capability names across backends.
 	ResolveConflicts(ctx context.Context, capabilities map[string]*BackendCapabilities) (*ResolvedCapabilities, error)
 
 	// MergeCapabilities creates the final unified capability view and routing table.
-	MergeCapabilities(ctx context.Context, resolved *ResolvedCapabilities) (*AggregatedCapabilities, error)
+	// Uses the backend registry to populate full BackendTarget information for routing.
+	MergeCapabilities(
+		ctx context.Context,
+		resolved *ResolvedCapabilities,
+		registry vmcp.BackendRegistry,
+	) (*AggregatedCapabilities, error)
+
+	// AggregateCapabilities is a convenience method that performs the full aggregation pipeline:
+	// 1. Query all backends
+	// 2. Resolve conflicts
+	// 3. Merge into final view
+	AggregateCapabilities(ctx context.Context, backends []vmcp.Backend) (*AggregatedCapabilities, error)
 }
 
 // BackendCapabilities contains the raw capabilities from a single backend.

pkg/vmcp/aggregator/cli_discoverer.go

@@ -0,0 +1,124 @@
+package aggregator
+
+import (
+	"context"
+	"fmt"
+
+	rt "github.com/stacklok/toolhive/pkg/container/runtime"
+	"github.com/stacklok/toolhive/pkg/groups"
+	"github.com/stacklok/toolhive/pkg/logger"
+	"github.com/stacklok/toolhive/pkg/vmcp"
+	"github.com/stacklok/toolhive/pkg/workloads"
+)
+
+// cliBackendDiscoverer discovers backend MCP servers from Docker/Podman workloads in a group.
+// This is the CLI version of BackendDiscoverer that uses the workloads.Manager.
+type cliBackendDiscoverer struct {
+	workloadsManager workloads.Manager
+	groupsManager    groups.Manager
+}
+
+// NewCLIBackendDiscoverer creates a new CLI-based backend discoverer.
+// It discovers workloads from Docker/Podman containers managed by ToolHive.
+func NewCLIBackendDiscoverer(workloadsManager workloads.Manager, groupsManager groups.Manager) BackendDiscoverer {
+	return &cliBackendDiscoverer{
+		workloadsManager: workloadsManager,
+		groupsManager:    groupsManager,
+	}
+}
+
+// Discover finds all backend workloads in the specified group.
+// Returns all accessible backends with their health status marked based on workload status.
+// The groupRef is the group name (e.g., "engineering-team").
+func (d *cliBackendDiscoverer) Discover(ctx context.Context, groupRef string) ([]vmcp.Backend, error) {
+	logger.Infof("Discovering backends in group %s", groupRef)
+
+	// Verify that the group exists
+	exists, err := d.groupsManager.Exists(ctx, groupRef)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check if group exists: %w", err)
+	}
+	if !exists {
+		return nil, fmt.Errorf("group %s not found", groupRef)
+	}
+
+	// Get all workload names in the group
+	workloadNames, err := d.workloadsManager.ListWorkloadsInGroup(ctx, groupRef)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list workloads in group: %w", err)
+	}
+
+	if len(workloadNames) == 0 {
+		logger.Infof("No workloads found in group %s", groupRef)
+		return []vmcp.Backend{}, nil
+	}
+
+	logger.Debugf("Found %d workloads in group %s, discovering backends", len(workloadNames), groupRef)
+
+	// Query each workload and convert to backend
+	var backends []vmcp.Backend
+	for _, name := range workloadNames {
+		workload, err := d.workloadsManager.GetWorkload(ctx, name)
+		if err != nil {
+			logger.Warnf("Failed to get workload %s: %v, skipping", name, err)
+			continue
+		}
+
+		// Skip workloads without a URL (not accessible)
+		if workload.URL == "" {
+			logger.Debugf("Skipping workload %s without URL", name)
+			continue
+		}
+
+		// Map workload status to backend health status
+		healthStatus := mapWorkloadStatusToHealth(workload.Status)
+
+		// Convert core.Workload to vmcp.Backend
+		backend := vmcp.Backend{
+			ID:            name,
+			Name:          name,
+			BaseURL:       workload.URL,
+			TransportType: workload.TransportType.String(),
+			HealthStatus:  healthStatus,
+			Metadata:      make(map[string]string),
+		}
+
+		// Copy user labels to metadata first
+		for k, v := range workload.Labels {
+			backend.Metadata[k] = v
+		}
+
+		// Set system metadata (these override user labels to prevent conflicts)
+		backend.Metadata["group"] = groupRef
+		backend.Metadata["tool_type"] = workload.ToolType
+		backend.Metadata["workload_status"] = string(workload.Status)
+
+		backends = append(backends, backend)
+		logger.Debugf("Discovered backend %s: %s (%s) with health status %s",
+			backend.ID, backend.BaseURL, backend.TransportType, backend.HealthStatus)
+	}
+
+	if len(backends) == 0 {
+		logger.Infof("No accessible backends found in group %s (all workloads lack URLs)", groupRef)
+		return []vmcp.Backend{}, nil
+	}
+
+	logger.Infof("Discovered %d backends in group %s", len(backends), groupRef)
+	return backends, nil
+}
+
+// mapWorkloadStatusToHealth converts a workload status to a backend health status.
+func mapWorkloadStatusToHealth(status rt.WorkloadStatus) vmcp.BackendHealthStatus {
+	switch status {
+	case rt.WorkloadStatusRunning:
+		return vmcp.BackendHealthy
+	case rt.WorkloadStatusUnhealthy:
+		return vmcp.BackendUnhealthy
+	case rt.WorkloadStatusStopped, rt.WorkloadStatusError, rt.WorkloadStatusStopping, rt.WorkloadStatusRemoving:
+		return vmcp.BackendUnhealthy
+	case rt.WorkloadStatusStarting, rt.WorkloadStatusUnknown:
+		return vmcp.BackendUnknown
+	default:
+		return vmcp.BackendUnknown
+	}
+}