Add tags in lexical order as required by AddTag()

sinks/httpSink.go

@@ -44,13 +44,19 @@ type HttpSinkConfig struct {
 
 type HttpSink struct {
 	sink
-	client  *http.Client
+	client *http.Client
+	// influx line protocol encoder
 	encoder influx.Encoder
-	// Flush() runs in another goroutine, so this encoderLock has to protect the encoder
+	// Flush() runs in another goroutine and accesses the influx line protocol encoder,
+	// so this encoderLock has to protect the encoder
 	encoderLock sync.Mutex
-	timerLock   sync.Mutex
-	flushTimer  *time.Timer
-	config      HttpSinkConfig
+
+	// timer to run Flush()
+	flushTimer *time.Timer
+	// Lock to assure that only one timer is running at a time
+	timerLock sync.Mutex
+
+	config HttpSinkConfig
 }
 
 // Write sends metric m as http message
@@ -62,18 +68,24 @@ func (s *HttpSink) Write(m lp.CCMetric) error {
 	// Encode measurement name
 	s.encoder.StartLine(m.Name())
 
-	// Encode tags
+	// copy tags and meta data which should be used as tags
+	tags := make(map[string]string)
+	keys := make([]string, 0)
 	for key, value := range m.Tags() {
-		s.encoder.AddTag(key, value)
+		keys = append(keys, key)
+		tags[key] = value
+	}
+	for _, key := range s.config.MetaAsTags {
+		if value, ok := m.GetMeta(key); ok {
+			keys = append(keys, key)
+			tags[key] = value
+		}
 	}
 
-	// Encode metadata as tags
-	for key, use_meta_as_tag := range s.meta_as_tags {
-		if use_meta_as_tag {
-			if val, ok := m.GetMeta(key); ok {
-				s.encoder.AddTag(key, val)
-			}
-		}
+	// Encode tags
+	slices.Sort(keys)
+	for _, key := range keys {
+		s.encoder.AddTag(key, tags[key])
 	}
 
 	// Encode fields
@@ -234,11 +246,8 @@ func NewHttpSink(name string, config json.RawMessage) (Sink, error) {
 			cclog.ComponentDebug(s.name, "flushDelay", t)
 		}
 	}
-	// Create lookup map to use meta infos as tags in the output metric
-	s.meta_as_tags = make(map[string]bool)
-	for _, k := range s.config.MetaAsTags {
-		s.meta_as_tags[k] = true
-	}
+
+	// Create http client
 	s.client = &http.Client{
 		Transport: &http.Transport{
 			MaxIdleConns:    1, // We will only ever talk to one host.
@@ -246,6 +255,9 @@ func NewHttpSink(name string, config json.RawMessage) (Sink, error) {
 		},
 		Timeout: s.config.timeout,
 	}
+
+	// Configure influx line protocol encoder
 	s.encoder.SetPrecision(influx.Second)
+
 	return s, nil
 }