fix(faro/receiver): extra_log_labels with empty value now map to exis…

…ting value in log line (#632)

Signed-off-by: hainenber <[email protected]>

CHANGELOG.md

@@ -43,6 +43,9 @@ Main (unreleased)
 
 - In `mimir.rules.kubernetes`, fix an issue where unrecoverable errors from the Mimir API were retried. (@56quarters)
 
+- Flow: Fix an issue where `faro.receiver`'s `extra_log_labels` with empty value don't
+  map existing value in log line. (@hainenber)
+
 ### Other changes
 
 - Update `alloy-mixin` to use more specific alert group names (for example,

internal/component/faro/receiver/exporters.go

@@ -3,6 +3,7 @@ package receiver
 import (
 	"context"
 	"errors"
+	"fmt"
 	"sync"
 	"time"
 
@@ -158,7 +159,7 @@ func (exp *logsExporter) sendKeyValsToLogsPipeline(ctx context.Context, kv *payl
 	}
 
 	ent := loki.Entry{
-		Labels: exp.labelSet(),
+		Labels: exp.labelSet(kv),
 		Entry: logproto.Entry{
 			Timestamp: time.Now(),
 			Line:      string(line),
@@ -180,10 +181,23 @@ func (exp *logsExporter) sendKeyValsToLogsPipeline(ctx context.Context, kv *payl
 	return nil
 }
 
-func (exp *logsExporter) labelSet() model.LabelSet {
+func (exp *logsExporter) labelSet(kv *payload.KeyVal) model.LabelSet {
 	exp.labelsMut.RLock()
 	defer exp.labelsMut.RUnlock()
-	return exp.labels
+
+	// Attach extra label to log lines
+	set := make(model.LabelSet, len(exp.labels))
+	for k, v := range exp.labels {
+		if len(v) > 0 {
+			set[k] = v
+		} else {
+			if val, ok := kv.Get(string(k)); ok {
+				set[k] = model.LabelValue(fmt.Sprint(val))
+			}
+		}
+	}
+
+	return set
 }
 
 func (exp *logsExporter) SetLabels(newLabels map[string]string) {

internal/component/faro/receiver/receiver_test.go

@@ -36,7 +36,8 @@ func Test(t *testing.T) {
 	go func() {
 		err := ctrl.Run(ctx, Arguments{
 			LogLabels: map[string]string{
-				"foo": "bar",
+				"foo":  "bar",
+				"kind": "",
 			},
 
 			Server: ServerArguments{
@@ -100,7 +101,8 @@ func Test(t *testing.T) {
 
 	expect := loki.Entry{
 		Labels: model.LabelSet{
-			"foo": model.LabelValue("bar"),
+			"foo":  model.LabelValue("bar"),
+			"kind": model.LabelValue("log"),
 		},
 		Entry: logproto.Entry{
 			Line: `timestamp="2021-01-01 00:00:00 +0000 UTC" kind=log message="hello, world" level=info context_env=dev traceID=0 spanID=0 browser_mobile=false`,