rcserver: implement prometheus metrics on a dedicated port - fixes #7940

fs/rc/rcserver/metrics.go

@@ -0,0 +1,97 @@
+// Package rcserver implements the HTTP endpoint to serve the remote control
+package rcserver
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/rclone/rclone/fs/accounting"
+	"github.com/rclone/rclone/fs/fshttp"
+	"github.com/rclone/rclone/fs/rc"
+	"github.com/rclone/rclone/fs/rc/jobs"
+	libhttp "github.com/rclone/rclone/lib/http"
+)
+
+const path = "/metrics"
+
+var promHandlerFunc http.HandlerFunc
+
+func init() {
+	rcloneCollector := accounting.NewRcloneCollector(context.Background())
+	prometheus.MustRegister(rcloneCollector)
+
+	m := fshttp.NewMetrics("rclone")
+	for _, c := range m.Collectors() {
+		prometheus.MustRegister(c)
+	}
+	fshttp.DefaultMetrics = m
+
+	promHandlerFunc = promhttp.Handler().ServeHTTP
+}
+
+// MetricsStart the remote control server if configured
+//
+// If the server wasn't configured the *Server returned may be nil
+func MetricsStart(ctx context.Context, opt *rc.Options) (*MetricsServer, error) {
+	jobs.SetOpt(opt) // set the defaults for jobs
+	if opt.MetricsHTTP.ListenAddr[0] != "" {
+		// Serve on the DefaultServeMux so can have global registrations appear
+		s, err := newMetricsServer(ctx, opt)
+		if err != nil {
+			return nil, err
+		}
+		return s, s.Serve()
+	}
+	return nil, nil
+}
+
+// MetricsServer contains everything to run the rc server
+type MetricsServer struct {
+	ctx             context.Context // for global config
+	server          *libhttp.Server
+	promHandlerFunc http.Handler
+	opt             *rc.Options
+}
+
+func newMetricsServer(ctx context.Context, opt *rc.Options) (*MetricsServer, error) {
+	s := &MetricsServer{
+		ctx:             ctx,
+		opt:             opt,
+		promHandlerFunc: promHandlerFunc,
+	}
+
+	var err error
+	s.server, err = libhttp.NewServer(ctx,
+		libhttp.WithConfig(opt.MetricsHTTP),
+		libhttp.WithAuth(opt.MetricsAuth),
+		libhttp.WithTemplate(opt.MetricsTemplate),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("failed to init server: %w", err)
+	}
+
+	router := s.server.Router()
+	router.Get(path, promHandlerFunc)
+	return s, nil
+}
+
+// Serve runs the http server in the background.
+//
+// Use s.Close() and s.Wait() to shutdown server
+func (s *MetricsServer) Serve() error {
+	s.server.Serve()
+	return nil
+}
+
+// Wait blocks while the server is serving requests
+func (s *MetricsServer) Wait() {
+	s.server.Wait()
+}
+
+// Shutdown gracefully shuts down the server
+func (s *MetricsServer) Shutdown() error {
+	return s.server.Shutdown()
+}