delete tag if tagvalue is -

conf/input.tomcat/tomcat.toml

@@ -17,7 +17,7 @@
 # interval_times = 1
 
 # important! use global unique string to specify instance
-# labels = { instance="192.168.1.2:8080", service="tomcat" }
+# labels = { instance="192.168.1.2:8080", url="-" }
 
 ## Optional TLS Config
 # use_tls = false

inputs/inputs.go

@@ -37,6 +37,9 @@ func NewSample(metric string, value interface{}, labels ...map[string]string) *t
 
 	for i := 0; i < len(labels); i++ {
 		for k, v := range labels[i] {
+			if v == "-" {
+				continue
+			}
 			s.Labels[k] = v
 		}
 	}