From 7520d5aac24803ded0f37fef62bbcf1873e11fd0 Mon Sep 17 00:00:00 2001
From: Bas Breijer <b.breijer@eaglescience.nl>
Date: Thu, 17 Apr 2025 15:25:22 +0200
Subject: [PATCH] revive PR 200: feat(loki): support go template in stream
 labels

---
 pkg/sinks/loki.go      | 23 ++++++++++++--
 pkg/sinks/loki_test.go | 68 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 3 deletions(-)
 create mode 100644 pkg/sinks/loki_test.go

diff --git a/pkg/sinks/loki.go b/pkg/sinks/loki.go
index 4d0a0d93..5f3c85a2 100644
--- a/pkg/sinks/loki.go
+++ b/pkg/sinks/loki.go
@@ -7,7 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/resmoio/kubernetes-event-exporter/pkg/kube"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strconv"
 	"time"
@@ -51,15 +51,32 @@ func generateTimestamp() string {
 	return strconv.FormatInt(time.Now().Unix(), 10) + "000000000"
 }
 
+func convertStreamTemplate(layout map[string]string, ev *kube.EnhancedEvent) (map[string]string, error) {
+	result := make(map[string]string)
+	for key, value := range layout {
+		rendered, err := GetString(ev, value)
+		if err != nil {
+			return nil, err
+		}
+
+		result[key] = rendered
+	}
+	return result, nil
+}
+
 func (l *Loki) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
 	eventBody, err := serializeEventWithLayout(l.cfg.Layout, ev)
 	if err != nil {
 		return err
 	}
+	streamLabels, err := convertStreamTemplate(l.cfg.StreamLabels, ev)
+	if err != nil {
+		return err
+	}
 	timestamp := generateTimestamp()
 	a := LokiMsg{
 		Streams: []promtailStream{{
-			Stream: l.cfg.StreamLabels,
+			Stream: streamLabels,
 			Values: [][]string{{timestamp, string(eventBody)}},
 		}},
 	}
@@ -93,7 +110,7 @@ func (l *Loki) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
 
 	defer resp.Body.Close()
 
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return err
 	}
diff --git a/pkg/sinks/loki_test.go b/pkg/sinks/loki_test.go
new file mode 100644
index 00000000..6b08a7a8
--- /dev/null
+++ b/pkg/sinks/loki_test.go
@@ -0,0 +1,68 @@
+package sinks
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"time"
+
+	"testing"
+
+	"github.com/resmoio/kubernetes-event-exporter/pkg/kube"
+	"github.com/stretchr/testify/assert"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestLoki_Send(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer ts.Close()
+	client := Loki{cfg: &LokiConfig{URL: ts.URL}}
+
+	err := client.Send(context.Background(), &kube.EnhancedEvent{})
+
+	assert.NoError(t, err)
+}
+
+func TestLoki_Send_StreamLabelsTemplated(t *testing.T) {
+	rr := httptest.NewRecorder()
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		result, err := io.ReadAll(r.Body)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		rr.Write(result)
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer ts.Close()
+	client := Loki{cfg: &LokiConfig{
+		URL: ts.URL,
+		StreamLabels: map[string]string{
+			"app":              "kube-events",
+			"object_namespace": "{{ .InvolvedObject.Namespace }}",
+		}}}
+
+	ev := &kube.EnhancedEvent{}
+	ev.Namespace = "default"
+	ev.Reason = "my reason"
+	ev.Type = "Warning"
+	ev.InvolvedObject.Kind = "Pod"
+	ev.InvolvedObject.Name = "nginx-server-123abc-456def"
+	ev.InvolvedObject.Namespace = "prod"
+	ev.Message = "Successfully pulled image \"nginx:latest\""
+	ev.FirstTimestamp = v1.Time{Time: time.Now()}
+
+	err := client.Send(context.Background(), ev)
+	assert.NoError(t, err)
+
+	var res LokiMsg
+	err = json.Unmarshal(rr.Body.Bytes(), &res)
+	assert.NoError(t, err)
+
+	assert.Equal(t, res.Streams[0].Stream["app"], "kube-events", "Non template labels should remain the same")
+	assert.Equal(t, res.Streams[0].Stream["object_namespace"], "prod", "Template labels should be templated")
+}