add some debug log

conf/input.ping/ping.toml

@@ -3,12 +3,12 @@
 
 [[instances]]
 # send ping packets to
-targets = [
-    "www.baidu.com",
-    "127.0.0.1",
-    "10.4.5.6",
-    "10.4.5.7"
-]
+# targets = [
+#     "www.baidu.com",
+#     "127.0.0.1",
+#     "10.4.5.6",
+#     "10.4.5.7"
+# ]
 
 # # append some labels for series
 # labels = { region="cloud", product="n9e" }

inputs/ping/ping.go

@@ -143,6 +143,12 @@ func (p *Ping) gatherOnce(slist *list.SafeList, ins *PingInstance) {
 		}
 	}
 
+	if config.Config.DebugMode {
+		if len(ins.Targets) == 0 {
+			log.Println("D! ping targets empty")
+		}
+	}
+
 	wg := new(sync.WaitGroup)
 	for _, target := range ins.Targets {
 		wg.Add(1)