Add rule about 'localhost'

config.go

@@ -135,6 +135,11 @@ var header = `# Tivan configuration
 # Use 'tivan -config tivan.toml -test' to see what metrics a config
 # file would generate.
 
+# One rule that plugins conform is wherever a connection string
+# can be passed, the values '' and 'localhost' are treated specially.
+# They indicate to the plugin to use their own builtin configuration to
+# connect to the local system.
+
 # Configuration for influxdb server to send metrics to
 # [influxdb]
 # url = "http://10.20.2.4"

plugins/mysql/mysql.go

@@ -77,6 +77,10 @@ var mappings = []*mapping{
 }
 
 func (m *Mysql) gatherServer(serv string, acc plugins.Accumulator) error {
+	if serv == "localhost" {
+		serv = ""
+	}
+
 	db, err := sql.Open("mysql", serv)
 	if err != nil {
 		return err

plugins/postgresql/postgresql.go

@@ -69,7 +69,7 @@ func (p *Postgresql) Gather(acc plugins.Accumulator) error {
 }
 
 func (p *Postgresql) gatherServer(serv *Server, acc plugins.Accumulator) error {
-	if serv.Address == "" {
+	if serv.Address == "" || serv.Address == "localhost" {
 		serv = localhost
 	}
 

tivan.toml

@@ -7,6 +7,14 @@
 # to be active. Declaring a plugin means just specifying the name
 # as a section with no variables.
 
+# Use 'tivan -config tivan.toml -test' to see what metrics a config
+# file would generate.
+
+# One rule that plugins conform is wherever a connection string
+# can be passed, the values '' and 'localhost' are treated specially.
+# They indicate to the plugin to use their own builtin configuration to
+# connect to the local system.
+
 # Configuration for influxdb server to send metrics to
 # [influxdb]
 # url = "http://10.20.2.4"