Prometheus support (#450)

Co-authored-by: nils måsén <nils@piksel.se>
Co-authored-by: MihailITPlace <ya.halo-halo@yandex.ru>
Co-authored-by: Sebastiaan Tammer <sebastiaantammer@gmail.com>

pkg/api/update/update.go

@@ -0,0 +1,50 @@
+package update
+
+import (
+	"io"
+	"net/http"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+)
+
+var (
+	lock chan bool
+)
+
+// New is a factory function creating a new  Handler instance
+func New(updateFn func()) *Handler {
+	lock = make(chan bool, 1)
+	lock <- true
+
+	return &Handler{
+		fn:   updateFn,
+		Path: "/v1/update",
+	}
+}
+
+// Handler is an API handler used for triggering container update scans
+type Handler struct {
+	fn   func()
+	Path string
+}
+
+// Handle is the actual http.Handle function doing all the heavy lifting
+func (handle *Handler) Handle(w http.ResponseWriter, r *http.Request) {
+	log.Info("Updates triggered by HTTP API request.")
+
+	_, err := io.Copy(os.Stdout, r.Body)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	select {
+	case chanValue := <-lock:
+		defer func() { lock <- chanValue }()
+		handle.fn()
+	default:
+		log.Debug("Skipped. Another update already running.")
+	}
+
+}