Chore: Refactor grafana-server (#19796)

* Rename GrafanaServerImpl to Server

* Make flag dependencies explicit

* Extract method for building service graph

* Document and clarify methods

* Rename HttpServer to HTTPServer

pkg/cmd/grafana-server/main.go

@@ -37,16 +37,20 @@ var commit = "NA"
 var buildBranch = "master"
 var buildstamp string
 
-var configFile = flag.String("config", "", "path to config file")
-var homePath = flag.String("homepath", "", "path to grafana install/home path, defaults to working directory")
-var pidFile = flag.String("pidfile", "", "path to pid file")
-var packaging = flag.String("packaging", "unknown", "describes the way Grafana was installed")
-
 func main() {
-	v := flag.Bool("v", false, "prints current version and exits")
-	profile := flag.Bool("profile", false, "Turn on pprof profiling")
-	profilePort := flag.Int("profile-port", 6060, "Define custom port for profiling")
+	var (
+		configFile = flag.String("config", "", "path to config file")
+		homePath   = flag.String("homepath", "", "path to grafana install/home path, defaults to working directory")
+		pidFile    = flag.String("pidfile", "", "path to pid file")
+		packaging  = flag.String("packaging", "unknown", "describes the way Grafana was installed")
+
+		v           = flag.Bool("v", false, "prints current version and exits")
+		profile     = flag.Bool("profile", false, "Turn on pprof profiling")
+		profilePort = flag.Int("profile-port", 6060, "Define custom port for profiling")
+	)
+
 	flag.Parse()
+
 	if *v {
 		fmt.Printf("Version %s (commit: %s, branch: %s)\n", version, commit, buildBranch)
 		os.Exit(0)
@@ -88,13 +92,13 @@ func main() {
 
 	metrics.SetBuildInformation(version, commit, buildBranch)
 
-	server := NewGrafanaServer()
+	server := NewServer(*configFile, *homePath, *pidFile)
 
 	go listenToSystemSignals(server)
 
 	err := server.Run()
 
-	code := server.Exit(err)
+	code := server.ExitCode(err)
 	trace.Stop()
 	log.Close()
 
@@ -111,7 +115,7 @@ func validPackaging(packaging string) string {
 	return "unknown"
 }
 
-func listenToSystemSignals(server *GrafanaServerImpl) {
+func listenToSystemSignals(server *Server) {
 	signalChan := make(chan os.Signal, 1)
 	sighupChan := make(chan os.Signal, 1)
 

pkg/cmd/grafana-server/server.go

@@ -41,20 +41,26 @@ import (
 	"github.com/grafana/grafana/pkg/setting"
 )
 
-func NewGrafanaServer() *GrafanaServerImpl {
+// NewServer returns a new instance of Server.
+func NewServer(configFile, homePath, pidFile string) *Server {
 	rootCtx, shutdownFn := context.WithCancel(context.Background())
 	childRoutines, childCtx := errgroup.WithContext(rootCtx)
 
-	return &GrafanaServerImpl{
+	return &Server{
 		context:       childCtx,
 		shutdownFn:    shutdownFn,
 		childRoutines: childRoutines,
 		log:           log.New("server"),
 		cfg:           setting.NewCfg(),
+
+		configFile: configFile,
+		homePath:   homePath,
+		pidFile:    pidFile,
 	}
 }
 
-type GrafanaServerImpl struct {
+// Server is responsible for managing the lifecycle of services.
+type Server struct {
 	context            context.Context
 	shutdownFn         context.CancelFunc
 	childRoutines      *errgroup.Group
@@ -63,75 +69,48 @@ type GrafanaServerImpl struct {
 	shutdownReason     string
 	shutdownInProgress bool
 
+	configFile string
+	homePath   string
+	pidFile    string
+
 	RouteRegister routing.RouteRegister `inject:""`
-	HttpServer    *api.HTTPServer       `inject:""`
+	HTTPServer    *api.HTTPServer       `inject:""`
 }
 
-func (g *GrafanaServerImpl) Run() error {
-	var err error
-	g.loadConfiguration()
-	g.writePIDFile()
+// Run initializes and starts services. This will block until all services have
+// exited. To initiate shutdown, call the Shutdown method in another goroutine.
+func (s *Server) Run() error {
+	s.loadConfiguration()
+	s.writePIDFile()
 
 	login.Init()
 	social.NewOAuthService()
 
-	serviceGraph := inject.Graph{}
-	err = serviceGraph.Provide(&inject.Object{Value: bus.GetBus()})
-	if err != nil {
-		return fmt.Errorf("Failed to provide object to the graph: %v", err)
-	}
-	err = serviceGraph.Provide(&inject.Object{Value: g.cfg})
-	if err != nil {
-		return fmt.Errorf("Failed to provide object to the graph: %v", err)
-	}
-	err = serviceGraph.Provide(&inject.Object{Value: routing.NewRouteRegister(middleware.RequestMetrics, middleware.RequestTracing)})
-	if err != nil {
-		return fmt.Errorf("Failed to provide object to the graph: %v", err)
-	}
-	err = serviceGraph.Provide(&inject.Object{Value: localcache.New(5*time.Minute, 10*time.Minute)})
-	if err != nil {
-		return fmt.Errorf("Failed to provide object to the graph: %v", err)
-	}
-
-	// self registered services
 	services := registry.GetServices()
 
-	// Add all services to dependency graph
-	for _, service := range services {
-		err = serviceGraph.Provide(&inject.Object{Value: service.Instance})
-		if err != nil {
-			return fmt.Errorf("Failed to provide object to the graph: %v", err)
-		}
+	if err := s.buildServiceGraph(services); err != nil {
+		return err
 	}
 
-	err = serviceGraph.Provide(&inject.Object{Value: g})
-	if err != nil {
-		return fmt.Errorf("Failed to provide object to the graph: %v", err)
-	}
-
-	// Inject dependencies to services
-	if err := serviceGraph.Populate(); err != nil {
-		return fmt.Errorf("Failed to populate service dependency: %v", err)
-	}
-
-	// Init & start services
+	// Initialize services.
 	for _, service := range services {
 		if registry.IsDisabled(service.Instance) {
 			continue
 		}
 
-		g.log.Info("Initializing " + service.Name)
+		s.log.Info("Initializing " + service.Name)
 
 		if err := service.Instance.Init(); err != nil {
 			return fmt.Errorf("Service init failed: %v", err)
 		}
 	}
 
-	// Start background services
-	for _, srv := range services {
-		// variable needed for accessing loop variable in function callback
-		descriptor := srv
-		service, ok := srv.Instance.(registry.BackgroundService)
+	// Start background services.
+	for _, svc := range services {
+		// Variable is needed for accessing loop variable in function callback
+		descriptor := svc
+
+		service, ok := svc.Instance.(registry.BackgroundService)
 		if !ok {
 			continue
 		}
@@ -140,98 +119,140 @@ func (g *GrafanaServerImpl) Run() error {
 			continue
 		}
 
-		g.childRoutines.Go(func() error {
-			// Skip starting new service when shutting down
-			// Can happen when service stop/return during startup
-			if g.shutdownInProgress {
+		s.childRoutines.Go(func() error {
+			// Don't start new services when server is shutting down.
+			if s.shutdownInProgress {
 				return nil
 			}
 
-			err := service.Run(g.context)
-
-			// If error is not canceled then the service crashed
-			if err != context.Canceled && err != nil {
-				g.log.Error("Stopped "+descriptor.Name, "reason", err)
+			if err := service.Run(s.context); err != nil {
+				if err != context.Canceled {
+					// Server has crashed.
+					s.log.Error("Stopped "+descriptor.Name, "reason", err)
 				} else {
-				g.log.Info("Stopped "+descriptor.Name, "reason", err)
+					s.log.Info("Stopped "+descriptor.Name, "reason", err)
+				}
 			}
 
-			// Mark that we are in shutdown mode
-			// So more services are not started
-			g.shutdownInProgress = true
-			return err
+			s.shutdownInProgress = true
+
+			return nil
 		})
 	}
 
-	sendSystemdNotification("READY=1")
+	notifySystemd("READY=1")
 
-	return g.childRoutines.Wait()
+	return s.childRoutines.Wait()
 }
 
-func (g *GrafanaServerImpl) loadConfiguration() {
-	err := g.cfg.Load(&setting.CommandLineArgs{
-		Config:   *configFile,
-		HomePath: *homePath,
-		Args:     flag.Args(),
-	})
-
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Failed to start grafana. error: %s\n", err.Error())
-		os.Exit(1)
-	}
-
-	g.log.Info("Starting "+setting.ApplicationName, "version", version, "commit", commit, "branch", buildBranch, "compiled", time.Unix(setting.BuildStamp, 0))
-	g.cfg.LogConfigSources()
-}
-
-func (g *GrafanaServerImpl) Shutdown(reason string) {
-	g.log.Info("Shutdown started", "reason", reason)
-	g.shutdownReason = reason
-	g.shutdownInProgress = true
+// Shutdown initiates a shutdown of the services, and waits for all services to
+// exit.
+func (s *Server) Shutdown(reason string) {
+	s.log.Info("Shutdown started", "reason", reason)
+	s.shutdownReason = reason
+	s.shutdownInProgress = true
 
 	// call cancel func on root context
-	g.shutdownFn()
+	s.shutdownFn()
 
 	// wait for child routines
-	g.childRoutines.Wait()
+	s.childRoutines.Wait()
 }
 
-func (g *GrafanaServerImpl) Exit(reason error) int {
-	// default exit code is 1
+// ExitCode returns an exit code for a given error.
+func (s *Server) ExitCode(reason error) int {
 	code := 1
 
-	if reason == context.Canceled && g.shutdownReason != "" {
-		reason = fmt.Errorf(g.shutdownReason)
+	if reason == context.Canceled && s.shutdownReason != "" {
+		reason = fmt.Errorf(s.shutdownReason)
 		code = 0
 	}
 
-	g.log.Error("Server shutdown", "reason", reason)
+	s.log.Error("Server shutdown", "reason", reason)
+
 	return code
 }
 
-func (g *GrafanaServerImpl) writePIDFile() {
-	if *pidFile == "" {
+// writePIDFile retrieves the current process ID and writes it to file.
+func (s *Server) writePIDFile() {
+	if s.pidFile == "" {
 		return
 	}
 
 	// Ensure the required directory structure exists.
-	err := os.MkdirAll(filepath.Dir(*pidFile), 0700)
+	err := os.MkdirAll(filepath.Dir(s.pidFile), 0700)
 	if err != nil {
-		g.log.Error("Failed to verify pid directory", "error", err)
+		s.log.Error("Failed to verify pid directory", "error", err)
 		os.Exit(1)
 	}
 
-	// Retrieve the PID and write it.
+	// Retrieve the PID and write it to file.
 	pid := strconv.Itoa(os.Getpid())
-	if err := ioutil.WriteFile(*pidFile, []byte(pid), 0644); err != nil {
-		g.log.Error("Failed to write pidfile", "error", err)
+	if err := ioutil.WriteFile(s.pidFile, []byte(pid), 0644); err != nil {
+		s.log.Error("Failed to write pidfile", "error", err)
 		os.Exit(1)
 	}
 
-	g.log.Info("Writing PID file", "path", *pidFile, "pid", pid)
+	s.log.Info("Writing PID file", "path", s.pidFile, "pid", pid)
 }
 
-func sendSystemdNotification(state string) error {
+// buildServiceGraph builds a graph of services and their dependencies.
+func (s *Server) buildServiceGraph(services []*registry.Descriptor) error {
+	// Specify service dependencies.
+	objs := []interface{}{
+		bus.GetBus(),
+		s.cfg,
+		routing.NewRouteRegister(middleware.RequestMetrics, middleware.RequestTracing),
+		localcache.New(5*time.Minute, 10*time.Minute),
+		s,
+	}
+
+	for _, service := range services {
+		objs = append(objs, service.Instance)
+	}
+
+	var serviceGraph inject.Graph
+
+	// Provide services and their dependencies to the graph.
+	for _, obj := range objs {
+		if err := serviceGraph.Provide(&inject.Object{Value: obj}); err != nil {
+			return fmt.Errorf("Failed to provide object to the graph: %v", err)
+		}
+	}
+
+	// Resolve services and their dependencies.
+	if err := serviceGraph.Populate(); err != nil {
+		return fmt.Errorf("Failed to populate service dependency: %v", err)
+	}
+
+	return nil
+}
+
+// loadConfiguration loads settings and configuration from config files.
+func (s *Server) loadConfiguration() {
+	args := &setting.CommandLineArgs{
+		Config:   s.configFile,
+		HomePath: s.homePath,
+		Args:     flag.Args(),
+	}
+
+	if err := s.cfg.Load(args); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to start grafana. error: %s\n", err.Error())
+		os.Exit(1)
+	}
+
+	s.log.Info("Starting "+setting.ApplicationName,
+		"version", version,
+		"commit", commit,
+		"branch", buildBranch,
+		"compiled", time.Unix(setting.BuildStamp, 0),
+	)
+
+	s.cfg.LogConfigSources()
+}
+
+// notifySystemd sends state notifications to systemd.
+func notifySystemd(state string) error {
 	notifySocket := os.Getenv("NOTIFY_SOCKET")
 
 	if notifySocket == "" {
@@ -244,14 +265,12 @@ func sendSystemdNotification(state string) error {
 	}
 
 	conn, err := net.DialUnix(socketAddr.Net, nil, socketAddr)
-
 	if err != nil {
 		return err
 	}
+	defer conn.Close()
 
 	_, err = conn.Write([]byte(state))
 
-	conn.Close()
-
 	return err
 }