[Agent Management] Support External Labels from API

pkg/config/agent_management_remote_config_test.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/grafana/agent/pkg/metrics/instance"
+	"github.com/prometheus/prometheus/model/labels"
 	"github.com/stretchr/testify/require"
 )
 
@@ -179,4 +180,77 @@ integration_configs:
 		require.Equal(t, true, c.Integrations.ConfigV1.ReplaceInstanceLabel)
 		require.Equal(t, 5*time.Second, c.Integrations.ConfigV1.IntegrationRestartBackoff)
 	})
+
+	t.Run("no external labels provided", func(t *testing.T) {
+		rc := RemoteConfig{
+			BaseConfig: BaseConfigContent(baseConfig),
+			Snippets:   allSnippets,
+		}
+		c, err := rc.BuildAgentConfig()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(c.Logs.Configs))
+		require.Empty(t, c.Metrics.Global.Prometheus.ExternalLabels)
+	})
+
+	t.Run("no external labels provided in remote config", func(t *testing.T) {
+		baseConfig := `
+server:
+    log_level: debug
+metrics:
+    global:
+        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.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) {
+		rc := RemoteConfig{
+			BaseConfig: BaseConfigContent(baseConfig),
+			Snippets:   allSnippets,
+			AgentMetadata: AgentMetadata{
+				ExternalLabels: map[string]string{
+					"foo": "bar",
+				},
+			},
+		}
+		c, err := rc.BuildAgentConfig()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(c.Logs.Configs))
+		require.Equal(t, 1, len(c.Metrics.Configs))
+		require.Contains(t, c.Metrics.Global.Prometheus.ExternalLabels, labels.Label{Name: "foo", Value: "bar"})
+	})
+
+	t.Run("external labels don't override base config", func(t *testing.T) {
+		baseConfig := `
+server:
+    log_level: debug
+metrics:
+    global:
+        external_labels:
+            foo: bar
+`
+		rc := RemoteConfig{
+			BaseConfig: BaseConfigContent(baseConfig),
+			Snippets:   allSnippets,
+			AgentMetadata: AgentMetadata{
+				ExternalLabels: map[string]string{
+					"foo": "baz",
+				},
+			},
+		}
+		c, err := rc.BuildAgentConfig()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(c.Logs.Configs))
+		require.Equal(t, 1, len(c.Metrics.Configs))
+		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

@@ -6,13 +6,15 @@ import (
 	"github.com/grafana/agent/pkg/metrics/instance"
 	"github.com/grafana/loki/clients/pkg/promtail/scrapeconfig"
 	pc "github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/model/labels"
 	"gopkg.in/yaml.v2"
 )
 
 type (
 	RemoteConfig struct {
-		BaseConfig BaseConfigContent `json:"base_config" yaml:"base_config"`
-		Snippets   []Snippet         `json:"snippets" yaml:"snippets"`
+		BaseConfig    BaseConfigContent `json:"base_config" yaml:"base_config"`
+		Snippets      []Snippet         `json:"snippets" yaml:"snippets"`
+		AgentMetadata AgentMetadata     `json:"agent_metadata,omitempty" yaml:"agent_metadata,omitempty"`
 	}
 
 	// BaseConfigContent is the content of a base config
@@ -24,6 +26,10 @@ type (
 		Config string `json:"config" yaml:"config"`
 	}
 
+	AgentMetadata struct {
+		ExternalLabels map[string]string `json:"external_labels,omitempty" yaml:"external_labels,omitempty"`
+	}
+
 	// SnippetContent defines the internal structure of a snippet configuration.
 	SnippetContent struct {
 		// MetricsScrapeConfigs is a YAML containing list of metrics scrape configs.
@@ -63,6 +69,7 @@ func (rc *RemoteConfig) BuildAgentConfig() (*Config, error) {
 	if err != nil {
 		return nil, err
 	}
+	appendExternalLabels(&c, rc.AgentMetadata.ExternalLabels)
 	return &c, nil
 }
 
@@ -116,3 +123,18 @@ func appendSnippets(c *Config, snippets []Snippet) error {
 	c.Integrations.ConfigV1.Integrations = append(c.Integrations.ConfigV1.Integrations, integrationConfigs.Integrations...)
 	return nil
 }
+
+func appendExternalLabels(c *Config, externalLabels map[string]string) {
+	// Avoid doing anything if there are no external labels
+	if len(externalLabels) == 0 {
+		return
+	}
+	// Start off with the existing external labels, which will only be added to (not replaced)
+	newExternalLabels := c.Metrics.Global.Prometheus.ExternalLabels.Map()
+	for k, v := range externalLabels {
+		if _, ok := newExternalLabels[k]; !ok {
+			newExternalLabels[k] = v
+		}
+	}
+	c.Metrics.Global.Prometheus.ExternalLabels = labels.FromMap(newExternalLabels)
+}