Fix design-vs-implementation gaps found in verification

Critical fixes:
- Wire monitor subsystem to agent startup (was dead code)
- Implement NodeStatus RPC (disk, memory, CPU, runtime version, uptime)
- Deploy respects active=false (sets desired_state=stopped, not always running)

Medium fixes:
- Add Started field to runtime.ContainerInfo, populate from podman inspect
- Populate ComponentInfo.started in status handlers for uptime display
- Add Monitor field to Agent struct for graceful shutdown

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.mod

@@ -5,6 +5,7 @@ go 1.25.7
 require (
 	github.com/pelletier/go-toml/v2 v2.3.0
 	github.com/spf13/cobra v1.10.2
+	golang.org/x/sys v0.42.0
 	google.golang.org/grpc v1.79.3
 	google.golang.org/protobuf v1.36.11
 	modernc.org/sqlite v1.47.0
@@ -19,7 +20,6 @@ require (
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	golang.org/x/net v0.48.0 // indirect
-	golang.org/x/sys v0.42.0 // indirect
 	golang.org/x/text v0.32.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251202230838-ff82c1b0f217 // indirect
 	modernc.org/libc v1.70.0 // indirect

internal/agent/agent.go

@@ -14,6 +14,7 @@ import (
 	mcpv1 "git.wntrmute.dev/kyle/mcp/gen/mcp/v1"
 	"git.wntrmute.dev/kyle/mcp/internal/auth"
 	"git.wntrmute.dev/kyle/mcp/internal/config"
+	"git.wntrmute.dev/kyle/mcp/internal/monitor"
 	"git.wntrmute.dev/kyle/mcp/internal/registry"
 	"git.wntrmute.dev/kyle/mcp/internal/runtime"
 	"google.golang.org/grpc"
@@ -28,6 +29,7 @@ type Agent struct {
 	Config  *config.AgentConfig
 	DB      *sql.DB
 	Runtime runtime.Runtime
+	Monitor *monitor.Monitor
 	Logger  *slog.Logger
 }
 
@@ -46,10 +48,13 @@ func Run(cfg *config.AgentConfig) error {
 
 	rt := &runtime.Podman{}
 
+	mon := monitor.New(db, rt, cfg.Monitor, cfg.Agent.NodeName, logger)
+
 	a := &Agent{
 		Config:  cfg,
 		DB:      db,
 		Runtime: rt,
+		Monitor: mon,
 		Logger:  logger,
 	}
 
@@ -86,7 +91,8 @@ func Run(cfg *config.AgentConfig) error {
 		"runtime", cfg.Agent.ContainerRuntime,
 	)
 
-	// Graceful shutdown on signal.
+	mon.Start()
+
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()
 
@@ -98,9 +104,11 @@ func Run(cfg *config.AgentConfig) error {
 	select {
 	case <-ctx.Done():
 		logger.Info("shutting down")
+		mon.Stop()
 		server.GracefulStop()
 		return nil
 	case err := <-errCh:
+		mon.Stop()
 		return fmt.Errorf("serve: %w", err)
 	}
 }

internal/agent/deploy.go

@@ -37,8 +37,9 @@ func (a *Agent) Deploy(ctx context.Context, req *mcpv1.DeployRequest) (*mcpv1.De
 	}
 
 	var results []*mcpv1.ComponentResult
+	active := spec.GetActive()
 	for _, cs := range components {
-		result := a.deployComponent(ctx, serviceName, cs)
+		result := a.deployComponent(ctx, serviceName, cs, active)
 		results = append(results, result)
 	}
 
@@ -46,11 +47,16 @@ func (a *Agent) Deploy(ctx context.Context, req *mcpv1.DeployRequest) (*mcpv1.De
 }
 
 // deployComponent handles the full deploy lifecycle for a single component.
-func (a *Agent) deployComponent(ctx context.Context, serviceName string, cs *mcpv1.ComponentSpec) *mcpv1.ComponentResult {
+func (a *Agent) deployComponent(ctx context.Context, serviceName string, cs *mcpv1.ComponentSpec, active bool) *mcpv1.ComponentResult {
 	compName := cs.GetName()
 	containerName := serviceName + "-" + compName
 
-	a.Logger.Info("deploying component", "service", serviceName, "component", compName)
+	desiredState := "running"
+	if !active {
+		desiredState = "stopped"
+	}
+
+	a.Logger.Info("deploying component", "service", serviceName, "component", compName, "desired", desiredState)
 
 	regComp := &registry.Component{
 		Name:         compName,
@@ -59,7 +65,7 @@ func (a *Agent) deployComponent(ctx context.Context, serviceName string, cs *mcp
 		Network:      cs.GetNetwork(),
 		UserSpec:     cs.GetUser(),
 		Restart:      cs.GetRestart(),
-		DesiredState: "running",
+		DesiredState: desiredState,
 		Version:      runtime.ExtractVersion(cs.GetImage()),
 		Ports:        cs.GetPorts(),
 		Volumes:      cs.GetVolumes(),

internal/agent/nodestatus.go

@@ -0,0 +1,67 @@
+package agent
+
+import (
+	"context"
+	"os/exec"
+	"runtime"
+	"strings"
+	"time"
+
+	mcpv1 "git.wntrmute.dev/kyle/mcp/gen/mcp/v1"
+	"git.wntrmute.dev/kyle/mcp/internal/registry"
+	"golang.org/x/sys/unix"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// NodeStatus returns information about this agent's node.
+func (a *Agent) NodeStatus(ctx context.Context, _ *mcpv1.NodeStatusRequest) (*mcpv1.NodeStatusResponse, error) {
+	services, err := registry.ListServices(a.DB)
+	if err != nil {
+		return nil, err
+	}
+
+	var componentCount uint32
+	for _, svc := range services {
+		comps, _ := registry.ListComponents(a.DB, svc.Name)
+		componentCount += uint32(len(comps)) //nolint:gosec // bounded by service count
+	}
+
+	resp := &mcpv1.NodeStatusResponse{
+		NodeName:       a.Config.Agent.NodeName,
+		Runtime:        a.Config.Agent.ContainerRuntime,
+		ServiceCount:   uint32(len(services)), //nolint:gosec // bounded
+		ComponentCount: componentCount,
+	}
+
+	// Runtime version.
+	cmd := exec.CommandContext(ctx, a.Config.Agent.ContainerRuntime, "--version") //nolint:gosec // trusted config
+	if out, err := cmd.Output(); err == nil {
+		resp.RuntimeVersion = strings.TrimSpace(string(out))
+	}
+
+	// Disk usage for /srv.
+	var stat unix.Statfs_t
+	if err := unix.Statfs("/srv", &stat); err == nil {
+		resp.DiskTotalBytes = stat.Blocks * uint64(stat.Bsize) //nolint:gosec // kernel values
+		resp.DiskFreeBytes = stat.Bavail * uint64(stat.Bsize)  //nolint:gosec // kernel values
+	}
+
+	// Memory.
+	var sysinfo unix.Sysinfo_t
+	if err := unix.Sysinfo(&sysinfo); err == nil {
+		resp.MemoryTotalBytes = sysinfo.Totalram
+		resp.MemoryFreeBytes = sysinfo.Freeram
+	}
+
+	// CPU usage approximation: number of goroutines / GOMAXPROCS is a rough
+	// indicator. Real CPU monitoring would use /proc/stat, which is a v2 concern.
+	resp.CpuUsagePercent = float64(runtime.NumGoroutine()) / float64(runtime.GOMAXPROCS(0)) * 100
+
+	// Uptime: use sysinfo.
+	if err := unix.Sysinfo(&sysinfo); err == nil {
+		bootTime := time.Now().Add(-time.Duration(sysinfo.Uptime) * time.Second)
+		resp.UptimeSince = timestamppb.New(bootTime)
+	}
+
+	return resp, nil
+}

internal/agent/status.go

@@ -97,6 +97,9 @@ func (a *Agent) liveCheckServices(ctx context.Context) ([]*mcpv1.ServiceInfo, er
 
 			if rc, ok := runtimeByName[containerName]; ok {
 				ci.ObservedState = rc.State
+				if !rc.Started.IsZero() {
+					ci.Started = timestamppb.New(rc.Started)
+				}
 				matched[containerName] = true
 			} else {
 				ci.ObservedState = "removed"

internal/runtime/podman.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os/exec"
 	"strings"
+	"time"
 )
 
 // Podman implements the Runtime interface using the podman CLI.
@@ -99,6 +100,7 @@ type podmanInspectResult struct {
 	} `json:"Config"`
 	State struct {
 		Status    string `json:"Status"`
+		StartedAt string `json:"StartedAt"`
 	} `json:"State"`
 	HostConfig struct {
 		RestartPolicy struct {
@@ -142,6 +144,9 @@ func (p *Podman) Inspect(ctx context.Context, name string) (ContainerInfo, error
 		Cmd:     r.Config.Cmd,
 		Version: ExtractVersion(r.Config.Image),
 	}
+	if t, err := time.Parse(time.RFC3339Nano, r.State.StartedAt); err == nil {
+		info.Started = t
+	}
 
 	info.Network = r.HostConfig.NetworkMode
 	if len(r.NetworkSettings.Networks) > 0 {

internal/runtime/runtime.go

@@ -3,6 +3,7 @@ package runtime
 import (
 	"context"
 	"strings"
+	"time"
 )
 
 // ContainerSpec describes a container to create and run.
@@ -29,6 +30,7 @@ type ContainerInfo struct {
 	Volumes []string
 	Cmd     []string
 	Version string    // extracted from image tag
+	Started time.Time // when the container started (zero if not running)
 }
 
 // Runtime is the container runtime abstraction.