Agent Management: Introduce support for external labels in logs (#5786)

- We currently support remotely managing external labels for metrics.
    This change adds support for logs as well.
  - Note: this change only applies to static mode.

CHANGELOG.md

@@ -58,6 +58,8 @@ Main (unreleased)
   - `otelcol.processor.filter` - filters OTLP telemetry data using OpenTelemetry
     Transformation Language (OTTL). (@hainenber)
 
+- Agent Management: Introduce support for remotely managed external labels for logs. (@jcreixell)
+
 ### Enhancements
 
 - The `loki.write` WAL now has snappy compression enabled by default. (@thepalbi)

pkg/config/agent_management_remote_config_test.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/grafana/agent/pkg/metrics/instance"
+	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/stretchr/testify/require"
 )
@@ -199,19 +200,40 @@ server:
 metrics:
     global:
         external_labels:
-            foo: bar`
+            foo: bar
+logs:
+    global:
+        clients:
+        - external_labels:
+            foo: bar
+`
 		rc := RemoteConfig{
 			BaseConfig: BaseConfigContent(baseConfig),
 			Snippets:   allSnippets,
 		}
 		c, err := rc.BuildAgentConfig()
 		require.NoError(t, err)
 		require.Equal(t, 1, len(c.Logs.Configs))
+		require.Equal(t, 1, len(c.Logs.Global.ClientConfigs))
+		require.Equal(t, c.Logs.Global.ClientConfigs[0].ExternalLabels.LabelSet, model.LabelSet{"foo": "bar"})
 		require.Equal(t, 1, len(c.Metrics.Global.Prometheus.ExternalLabels))
 		require.Contains(t, c.Metrics.Global.Prometheus.ExternalLabels, labels.Label{Name: "foo", Value: "bar"})
 	})
 
 	t.Run("external labels provided", func(t *testing.T) {
+		baseConfig := `
+server:
+    log_level: debug
+metrics:
+    global:
+        remote_write:
+        - url: http://localhost:9090/api/prom/push
+logs:
+    global:
+        clients:
+        - url: http://localhost:3100/loki/api/v1/push
+`
+
 		rc := RemoteConfig{
 			BaseConfig: BaseConfigContent(baseConfig),
 			Snippets:   allSnippets,
@@ -225,6 +247,8 @@ metrics:
 		require.NoError(t, err)
 		require.Equal(t, 1, len(c.Logs.Configs))
 		require.Equal(t, 1, len(c.Metrics.Configs))
+		require.Equal(t, 1, len(c.Logs.Global.ClientConfigs))
+		require.Equal(t, c.Logs.Global.ClientConfigs[0].ExternalLabels.LabelSet, model.LabelSet{"foo": "bar"})
 		require.Contains(t, c.Metrics.Global.Prometheus.ExternalLabels, labels.Label{Name: "foo", Value: "bar"})
 	})
 
@@ -236,6 +260,11 @@ metrics:
     global:
         external_labels:
             foo: bar
+logs:
+    global:
+        clients:
+        - external_labels:
+            foo: bar
 `
 		rc := RemoteConfig{
 			BaseConfig: BaseConfigContent(baseConfig),
@@ -250,6 +279,8 @@ metrics:
 		require.NoError(t, err)
 		require.Equal(t, 1, len(c.Logs.Configs))
 		require.Equal(t, 1, len(c.Metrics.Configs))
+		require.Equal(t, 1, len(c.Logs.Global.ClientConfigs))
+		require.Equal(t, c.Logs.Global.ClientConfigs[0].ExternalLabels.LabelSet, model.LabelSet{"foo": "bar"})
 		require.Contains(t, c.Metrics.Global.Prometheus.ExternalLabels, labels.Label{Name: "foo", Value: "bar"})
 		require.NotContains(t, c.Metrics.Global.Prometheus.ExternalLabels, labels.Label{Name: "foo", Value: "baz"})
 	})

pkg/config/agentmanagement_remote_config.go

@@ -5,6 +5,7 @@ import (
 	"github.com/grafana/agent/pkg/logs"
 	"github.com/grafana/agent/pkg/metrics/instance"
 	"github.com/grafana/loki/clients/pkg/promtail/scrapeconfig"
+	"github.com/prometheus/common/model"
 	pc "github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/model/labels"
 	"gopkg.in/yaml.v2"
@@ -130,11 +131,20 @@ func appendExternalLabels(c *Config, externalLabels map[string]string) {
 		return
 	}
 	// Start off with the existing external labels, which will only be added to (not replaced)
-	newExternalLabels := c.Metrics.Global.Prometheus.ExternalLabels.Map()
+	metricsExternalLabels := c.Metrics.Global.Prometheus.ExternalLabels.Map()
 	for k, v := range externalLabels {
-		if _, ok := newExternalLabels[k]; !ok {
-			newExternalLabels[k] = v
+		if _, ok := metricsExternalLabels[k]; !ok {
+			metricsExternalLabels[k] = v
 		}
 	}
-	c.Metrics.Global.Prometheus.ExternalLabels = labels.FromMap(newExternalLabels)
+
+	logsExternalLabels := make(model.LabelSet)
+	for k, v := range externalLabels {
+		logsExternalLabels[model.LabelName(k)] = model.LabelValue(v)
+	}
+
+	c.Metrics.Global.Prometheus.ExternalLabels = labels.FromMap(metricsExternalLabels)
+	for i, cc := range c.Logs.Global.ClientConfigs {
+		c.Logs.Global.ClientConfigs[i].ExternalLabels.LabelSet = logsExternalLabels.Merge(cc.ExternalLabels.LabelSet)
+	}
 }