[Feature] Basic systemd service monitoring (#1153)

* basic systemd service monitoring

* update to work after /internal rename

* monitor systemd service cpu and memory usage

---------

Co-authored-by: henrygd <hank@henrygd.me>

agent/agent.go

@@ -31,6 +31,7 @@ type Agent struct {
 	netInterfaces     map[string]struct{}        // Stores all valid network interfaces
 	netIoStats        system.NetIoStats          // Keeps track of bandwidth usage
 	dockerManager     *dockerManager             // Manages Docker API requests
+	systemdManager    *systemdManager            // Manages systemd services
 	sensorConfig      *SensorConfig              // Sensors config
 	systemInfo        system.Info                // Host system info
 	gpuManager        *GPUManager                // Manages GPU data
@@ -88,6 +89,13 @@ func NewAgent(dataDir ...string) (agent *Agent, err error) {
 	// initialize docker manager
 	agent.dockerManager = newDockerManager(agent)
 
+	// initialize systemd manager
+	if sm, err := newSystemdManager(); err != nil {
+		slog.Debug("Systemd", "err", err)
+	} else {
+		agent.systemdManager = sm
+	}
+
 	// initialize GPU manager
 	if gm, err := NewGPUManager(); err != nil {
 		slog.Debug("GPU", "err", err)
@@ -137,6 +145,11 @@ func (a *Agent) gatherStats(sessionID string) *system.CombinedData {
 		}
 	}
 
+	if a.systemdManager != nil {
+		data.SystemdServices = a.systemdManager.getServiceStats()
+		slog.Debug("Systemd services", "data", data.SystemdServices)
+	}
+
 	data.Stats.ExtraFs = make(map[string]*system.FsStats)
 	for name, stats := range a.fsStats {
 		if !stats.Root && stats.DiskTotal > 0 {

agent/systemd.go

@@ -0,0 +1,107 @@
+//go:build linux
+
+package agent
+
+import (
+	"context"
+	"log/slog"
+	"math"
+	"strings"
+	"sync"
+
+	"github.com/coreos/go-systemd/v22/dbus"
+	"github.com/henrygd/beszel/internal/entities/systemd"
+)
+
+// systemdManager manages the collection of systemd service statistics.
+type systemdManager struct {
+	conn            *dbus.Conn
+	serviceStatsMap map[string]*systemd.Service
+	mu              sync.Mutex
+}
+
+// newSystemdManager creates a new systemdManager.
+func newSystemdManager() (*systemdManager, error) {
+	conn, err := dbus.New()
+	if err != nil {
+		if strings.Contains(err.Error(), "permission denied") {
+			slog.Error("Permission denied when connecting to systemd. Run as root or with appropriate user permissions.", "err", err)
+			return nil, err
+		}
+		slog.Error("Error connecting to systemd", "err", err)
+		return nil, err
+	}
+
+	return &systemdManager{
+		conn:            conn,
+		serviceStatsMap: make(map[string]*systemd.Service),
+	}, nil
+}
+
+// getServiceStats collects statistics for all running systemd services.
+func (sm *systemdManager) getServiceStats() []*systemd.Service {
+	units, err := sm.conn.ListUnitsContext(context.Background())
+	if err != nil {
+		slog.Error("Error listing systemd units", "err", err)
+		return nil
+	}
+
+	var services []*systemd.Service
+	for _, unit := range units {
+		if strings.HasSuffix(unit.Name, ".service") {
+			service := sm.updateServiceStats(unit)
+			services = append(services, service)
+		}
+	}
+	return services
+}
+
+// updateServiceStats updates the statistics for a single systemd service.
+func (sm *systemdManager) updateServiceStats(unit dbus.UnitStatus) *systemd.Service {
+	sm.mu.Lock()
+	defer sm.mu.Unlock()
+
+	props, err := sm.conn.GetUnitTypeProperties(unit.Name, "Service")
+	if err != nil {
+		slog.Debug("could not get unit type properties", "unit", unit.Name, "err", err)
+		return &systemd.Service{
+			Name:   unit.Name,
+			Status: unit.ActiveState,
+		}
+	}
+
+	var cpuUsage uint64
+	if val, ok := props["CPUUsageNSec"]; ok {
+		if v, ok := val.(uint64); ok {
+			cpuUsage = v
+		}
+	}
+
+	var memUsage uint64
+	if val, ok := props["MemoryCurrent"]; ok {
+		if v, ok := val.(uint64); ok {
+			memUsage = v
+		}
+	}
+
+	service, exists := sm.serviceStatsMap[unit.Name]
+	if !exists {
+		service = &systemd.Service{
+			Name:   unit.Name,
+			Status: unit.ActiveState,
+		}
+		sm.serviceStatsMap[unit.Name] = service
+	}
+
+	service.Status = unit.ActiveState
+
+	// If memUsage is MaxUint64 the api is saying it's not available, return 0
+	if memUsage == math.MaxUint64 {
+		memUsage = 0
+	}
+
+	service.Mem = float64(memUsage) / (1024 * 1024) // Convert to MB
+	service.CalculateCPUPercent(cpuUsage)
+
+	return service
+}

agent/systemd_unsupported.go

@@ -0,0 +1,18 @@
+//go:build !linux
+
+package agent
+
+import "github.com/henrygd/beszel/internal/entities/systemd"
+
+// systemdManager manages the collection of systemd service statistics.
+type systemdManager struct{}
+
+// newSystemdManager creates a new systemdManager.
+func newSystemdManager() (*systemdManager, error) {
+	return &systemdManager{}, nil
+}
+
+// getServiceStats returns nil for non-linux systems.
+func (sm *systemdManager) getServiceStats() []*systemd.Service {
+	return nil
+}