feat: show systemd service logs in service details (#2440)

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

internal/hub/api.go

@@ -15,6 +15,7 @@ import (
 	"github.com/blang/semver"
 	"github.com/henrygd/beszel"
 	"github.com/henrygd/beszel/internal/alerts"
+	systementity "github.com/henrygd/beszel/internal/entities/system"
 	"github.com/henrygd/beszel/internal/ghupdate"
 	"github.com/henrygd/beszel/internal/hub/config"
 	"github.com/henrygd/beszel/internal/hub/systems"
@@ -202,6 +203,8 @@ func (h *Hub) registerApiRoutes(se *core.ServeEvent) error {
 	apiAuth.POST("/zfs/refresh", h.refreshZfsData).BindFunc(excludeReadOnlyRole)
 	// get systemd service details
 	apiAuth.GET("/systemd/info", h.getSystemdInfo)
+	// get recent logs for a systemd service
+	apiAuth.GET("/systemd/logs", h.getSystemdLogs)
 	// get pending package updates
 	apiAuth.GET("/package-updates", h.getPackageUpdates)
 	// /containers routes
@@ -447,6 +450,44 @@ func (h *Hub) getSystemdInfo(e *core.RequestEvent) error {
 	return e.JSON(http.StatusOK, map[string]any{"details": details})
 }
 
+// getSystemdLogs handles GET /api/beszel/systemd/logs requests.
+func (h *Hub) getSystemdLogs(e *core.RequestEvent) error {
+	query := e.Request.URL.Query()
+	systemID := query.Get("system")
+	serviceName := query.Get("service")
+
+	if systemID == "" || serviceName == "" {
+		return e.BadRequestError("Invalid system or service parameter", nil)
+	}
+	system, err := h.sm.GetSystem(systemID)
+	if err != nil || !system.HasUser(e.App, e.Auth) {
+		return e.NotFoundError("", nil)
+	}
+	// Only fetch logs for services that are currently monitored on this system.
+	_, err = e.App.FindFirstRecordByFilter("systemd_services", "system = {:system} && name = {:name}", dbx.Params{
+		"system": systemID,
+		"name":   serviceName,
+	})
+	if err != nil {
+		return e.NotFoundError("", err)
+	}
+	// Old agents and agents without journal access do not advertise this capability.
+	systemRecord, err := e.App.FindRecordById("systems", systemID)
+	if err != nil {
+		return e.NotFoundError("", err)
+	}
+	var info systementity.Info
+	if err := systemRecord.UnmarshalJSONField("info", &info); err != nil || !info.SystemdLogs {
+		return e.JSON(http.StatusOK, map[string]string{"logs": ""})
+	}
+
+	logs, err := system.FetchSystemdLogsFromAgent(serviceName)
+	if err != nil {
+		return e.InternalServerError("", err)
+	}
+	return e.JSON(http.StatusOK, map[string]string{"logs": logs})
+}
+
 // getPackageUpdates handles GET /api/beszel/package-updates requests
 func (h *Hub) getPackageUpdates(e *core.RequestEvent) error {
 	systemID := e.Request.URL.Query().Get("system")

internal/hub/api_test.go

@@ -684,6 +684,25 @@ func TestApiRoutesAuthentication(t *testing.T) {
 				})
 			},
 		},
+		{
+			Name:   "GET /systemd/logs - old agent without capability returns empty logs",
+			Method: http.MethodGet,
+			URL:    fmt.Sprintf("/api/beszel/systemd/logs?system=%s&service=nginx.service", system.Id),
+			Headers: map[string]string{
+				"Authorization": userToken,
+			},
+			ExpectedStatus:  200,
+			ExpectedContent: []string{`"logs":""`},
+			TestAppFactory:  testAppFactory,
+			BeforeTestFunc: func(t testing.TB, app *pbTests.TestApp, e *core.ServeEvent) {
+				beszelTests.CreateRecord(app, "systemd_services", map[string]any{
+					"system": system.Id,
+					"name":   "nginx.service",
+					"state":  0,
+					"sub":    1,
+				})
+			},
+		},
 
 		// Auth Optional Routes - Should work without authentication
 		{

internal/hub/systems/system.go

@@ -777,6 +777,15 @@ func (sys *System) FetchSystemdInfoFromAgent(serviceName string) (systemd.Servic
 	return result, err
 }
 
+// FetchSystemdLogsFromAgent fetches recent journal entries for a systemd service from the agent.
+func (sys *System) FetchSystemdLogsFromAgent(serviceName string) (string, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	var result string
+	err := sys.request(ctx, common.GetSystemdLogs, common.SystemdLogsRequest{ServiceName: serviceName}, &result)
+	return result, err
+}
+
 // FetchSmartDataFromAgent fetches SMART data from the agent.
 func (sys *System) FetchSmartDataFromAgent() (smart.SmartDataResponse, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)

internal/hub/transport/transport.go

@@ -115,6 +115,16 @@ func unmarshalLegacyResponse(resp common.AgentResponse, action common.WebSocketA
 		}
 		*d = resp.ServiceInfo
 		return nil
+	case common.GetSystemdLogs:
+		d, ok := dest.(*string)
+		if !ok {
+			return fmt.Errorf("unexpected dest type for GetSystemdLogs: %T", dest)
+		}
+		if resp.String == nil {
+			return errors.New("no systemd logs in response")
+		}
+		*d = *resp.String
+		return nil
 	}
 	return fmt.Errorf("unsupported action: %d", action)
 }

internal/hub/transport/transport_test.go

@@ -31,3 +31,12 @@ func TestUnmarshalSmartDataResponse(t *testing.T) {
 		})
 	}
 }
+
+func TestUnmarshalSystemdLogsResponse(t *testing.T) {
+	logs := "2026-09-27T12:00:00+00:00 host nginx[1]: started"
+	response := common.AgentResponse{String: &logs}
+
+	var result string
+	require.NoError(t, UnmarshalResponse(response, common.GetSystemdLogs, &result))
+	assert.Equal(t, logs, result)
+}