abort parsing tags if malformed signalfx format, add tests

Signed-off-by: glightfoot <glightfoot@rsglab.com>

bridge_test.go

@@ -220,6 +220,26 @@ func TestHandlePacket(t *testing.T) {
 					CLabels:     map[string]string{},
 				},
 			},
+		}, {
+			name: "SignalFx tag extension, missing closing bracket",
+			in:   "[tag1=bar,tag2=bazfoo.test:100|c",
+			out: event.Events{
+				&event.CounterEvent{
+					CMetricName: "[tag1=bar,tag2=bazfoo.test",
+					CValue:      100,
+					CLabels:     map[string]string{},
+				},
+			},
+		}, {
+			name: "SignalFx tag extension, missing opening bracket",
+			in:   "tag1=bar,tag2=baz]foo.test:100|c",
+			out: event.Events{
+				&event.CounterEvent{
+					CMetricName: "tag1=bar,tag2=baz]foo.test",
+					CValue:      100,
+					CLabels:     map[string]string{},
+				},
+			},
 		}, {
 			name: "influxdb tag extension with tag keys unsupported by prometheus",
 			in:   "foo,09digits=0,tag.with.dots=1:100|c",

pkg/line/line.go

@@ -139,9 +139,16 @@ func parseNameAndTags(name string, labels map[string]string, tagErrors prometheu
 	startIdx := strings.IndexRune(name, '[')
 	endIdx := strings.IndexRune(name, ']')
 
-	if startIdx != -1 && endIdx != -1 {
+	switch {
+	case startIdx != -1 && endIdx != -1:
+		// good signalfx tags
 		parseNameTags(name[startIdx+1:endIdx], labels, tagErrors, logger)
 		return name[:startIdx] + name[endIdx+1:]
+	case (startIdx != -1) != (endIdx != -1):
+		// only one bracket, return unparsed
+		level.Debug(logger).Log("msg", "invalid SignalFx tags, not parsing", "metric", name)
+		tagErrors.Inc()
+		return name
 	}
 
 	for i, c := range name {