IG-11657: Add health check logs. (#38)

* IG-11657: Add health check logs.

* Revert change to imports.

* Add more logs.

web/web.go

@@ -341,13 +341,15 @@ func New(logger log.Logger, o *Options) *Handler {
 	router.Get("/-/healthy", func(w http.ResponseWriter, r *http.Request) {
 		if o.V3ioConfig == nil {
 			w.WriteHeader(http.StatusInternalServerError)
+			level.Warn(h.logger).Log("msg", "Prometheus is Unhealthy: still waiting on V3IO storage.")
 			fmt.Fprintf(w, "Prometheus is Unhealthy: still waiting on V3IO storage.\n")
 			return
 		}
 		schemaUrl := "http://" + path.Join(o.V3ioConfig.WebApiEndpoint, o.V3ioConfig.Container, o.V3ioConfig.TablePath, ".schema")
 		req, err := http.NewRequest("GET", schemaUrl, nil)
 		if err != nil {
 			w.WriteHeader(http.StatusInternalServerError)
+			level.Warn(h.logger).Log("msg", "Prometheus is Unhealthy.", "error", err)
 			fmt.Fprintf(w, "Prometheus is Unhealthy: %v\n", err)
 			return
 		}
@@ -363,24 +365,29 @@ func New(logger log.Logger, o *Options) *Handler {
 		resp, err := client.Do(req)
 		if err != nil {
 			w.WriteHeader(http.StatusInternalServerError)
+			level.Warn(h.logger).Log("msg", "Prometheus is Unhealthy.", "error", err)
 			fmt.Fprintf(w, "Prometheus is Unhealthy: %v\n", err)
 			return
 		}
 		if resp.StatusCode != http.StatusOK {
 			w.WriteHeader(http.StatusInternalServerError)
+			level.Warn(h.logger).Log("msg", "Prometheus is Unhealthy because it could not find schema file.", "schemaUrl", schemaUrl, "response", resp)
 			fmt.Fprintf(w, "Prometheus is Unhealthy because it could not find %s: %+v\n", schemaUrl, resp)
 			return
 		}
 		w.WriteHeader(http.StatusOK)
+		level.Info(h.logger).Log("msg", "Prometheus is Healthy.")
 		fmt.Fprintf(w, "Prometheus is Healthy.\n")
 	})
 	router.Get("/-/ready", readyf(func(w http.ResponseWriter, r *http.Request) {
 		if o.V3ioConfig == nil {
 			w.WriteHeader(http.StatusInternalServerError)
+			level.Warn(h.logger).Log("msg", "Prometheus is not ready: still waiting on V3IO storage.")
 			fmt.Fprintf(w, "Prometheus is not ready: still waiting on V3IO storage.\n")
 			return
 		}
 		w.WriteHeader(http.StatusOK)
+		level.Info(h.logger).Log("msg", "Prometheus is Ready.")
 		fmt.Fprintf(w, "Prometheus is Ready.\n")
 	}))