Fix dynamic label regex parsing behaviour

README.md

@@ -205,10 +205,11 @@ Label value: 202739
 
 ### Custom Label RegEx
 
-To override the default behavior a `interface_description_regex` can be supplied.  
+To override the default behavior a `interface_description_regex` can be supplied. This parameter can be given at a global level or per device. To use per-device regexes the target devices need to be defined in the exporter config. Per-device regex cannot be used in combination with `-config.ignore-targets`.
+
 #### Example
-The default regex `\[([^=\]]+)(=[^\]]+)?\]` would match interface descriptions like `"Description [foo] [bar=123]".  
-If we use `[[\s]([^=\[\]]+)(=[^,\]]+)?[,\]]` we can now match for `Description [foo, bar=123]` instead.  
+The default regex `\[([^=\]]+)(=[^\]]+)?\]` would match interface descriptions like `"Description [foo] [bar=123]"`.  
+If we use `[[\s]([^=\[\]]+)(=[^,\]]+)?[,\]]` we can now match for `"Description [foo, bar=123]"` instead.  
 
 
 ### Grafana Dashboards

junos_collector.go

@@ -50,10 +50,18 @@ func newJunosCollector(devices []*connector.Device, connectionManager *connector
 
 		if *dynamicIfaceLabels {
 			regex := defaultIfDescReg
-			if cfg.Devices[index].IfDescReg != "" {
-				regex = regexp.MustCompile(cfg.Devices[index].IfDescReg)
-			} else if cfg.IfDescReg != "" {
-				regex = regexp.MustCompile(cfg.IfDescReg)
+			if cfg.IfDescReg != "" {
+				regex, err = regexp.Compile(cfg.IfDescReg)
+				if err != nil {
+				        log.Errorf("Global dynamic label regex invalid: %s", cfg.IfDescReg)
+				        regex = defaultIfDescReg
+				}
+			} else if !(*ignoreConfigTargets) && index < len(cfg.Devices) && cfg.Devices[index].IfDescReg != "" {
+				regex, err = regexp.Compile(cfg.Devices[index].IfDescReg)
+				if err != nil {
+				     log.Errorf("Device specific dynamic label regex invalid: %s", cfg.Devices[index].IfDescReg)
+				     regex = defaultIfDescReg
+				}
 			}
 
 			err = l.CollectDescriptions(d, cl, regex)