kuma_sd: Extend Kuma SD configuration to allow users to specify ClientId

Signed-off-by: Marcin Skalski <skalskimarcin33@gmail.com>

config/config_test.go

@@ -568,6 +568,7 @@ var expectedConf = &Config{
 			ServiceDiscoveryConfigs: discovery.Configs{
 				&xds.KumaSDConfig{
 					Server:           "http://kuma-control-plane.kuma-system.svc:5676",
+					ClientId:         "main-prometheus",
 					HTTPClientConfig: config.DefaultHTTPClientConfig,
 					RefreshInterval:  model.Duration(15 * time.Second),
 					FetchTimeout:     model.Duration(2 * time.Minute),

config/testdata/conf.good.yml

@@ -221,6 +221,7 @@ scrape_configs:
 
     kuma_sd_configs:
       - server: http://kuma-control-plane.kuma-system.svc:5676
+        clientId: main-prometheus
 
   - job_name: service-marathon
     marathon_sd_configs:

config/testdata/roundtrip.good.yml

@@ -108,6 +108,7 @@ scrape_configs:
 
     kuma_sd_configs:
       - server: http://kuma-control-plane.kuma-system.svc:5676
+        clientId: main-prometheus
 
     marathon_sd_configs:
       - servers:

discovery/xds/kuma.go

@@ -178,10 +178,11 @@ func kumaMadsV1ResourceParser(resources []*anypb.Any, typeURL string) ([]model.L
 
 func NewKumaHTTPDiscovery(conf *KumaSDConfig, logger log.Logger) (discovery.Discoverer, error) {
 	// Default to "prometheus" if hostname is unavailable.
-	clientID, err := osutil.GetFQDN()
-	if err != nil {
-		level.Debug(logger).Log("msg", "error getting FQDN", "err", err)
-		clientID = "prometheus"
+	var clientID string
+	if conf.ClientId == "" {
+		clientID = defaultClientId(logger)
+	} else {
+		clientID = conf.ClientId
 	}
 
 	clientConfig := &HTTPResourceClientConfig{
@@ -215,3 +216,12 @@ func NewKumaHTTPDiscovery(conf *KumaSDConfig, logger log.Logger) (discovery.Disc
 
 	return d, nil
 }
+
+func defaultClientId(logger log.Logger) string {
+	clientID, err := osutil.GetFQDN()
+	if err != nil {
+		level.Debug(logger).Log("msg", "error getting FQDN", "err", err)
+		clientID = "prometheus"
+	}
+	return clientID
+}

discovery/xds/kuma_test.go

@@ -204,7 +204,7 @@ func TestNewKumaHTTPDiscovery(t *testing.T) {
 	require.True(t, ok)
 	require.Equal(t, kumaConf.Server, resClient.Server())
 	require.Equal(t, KumaMadsV1ResourceTypeURL, resClient.ResourceTypeURL())
-	require.NotEmpty(t, resClient.ID())
+	require.Equal(t, kumaConf.ClientId, resClient.ID())
 	require.Equal(t, KumaMadsV1ResourceType, resClient.config.ResourceType)
 }
 

discovery/xds/xds.go

@@ -55,6 +55,7 @@ type SDConfig struct {
 	RefreshInterval  model.Duration          `yaml:"refresh_interval,omitempty"`
 	FetchTimeout     model.Duration          `yaml:"fetch_timeout,omitempty"`
 	Server           string                  `yaml:"server,omitempty"`
+	ClientId         string                  `yaml:"clientId,omitempty"`
 }
 
 // mustRegisterMessage registers the provided message type in the typeRegistry, and panics

discovery/xds/xds_test.go

@@ -36,6 +36,7 @@ var (
 	sdConf = SDConfig{
 		Server:          "http://127.0.0.1",
 		RefreshInterval: model.Duration(10 * time.Second),
+		ClientId:        "test-id",
 	}
 
 	testFetchFailuresCount = prometheus.NewCounter(

docs/configuration/configuration.md

@@ -2230,6 +2230,11 @@ See below for the configuration options for Kuma MonitoringAssignment discovery:
 # Address of the Kuma Control Plane's MADS xDS server.
 server: <string>
 
+# Client id is used by Kuma Control Plane to compute Monitoring Assignment for specific Prometheus backend. 
+# This is useful when migrating between multiple Prometheus backends, or having separate backend for each Mesh
+# When not specified, system hostname/fqdn will be used if available, if not `prometheus` will be used.
+clientId: <string>
+
 # The time to wait between polling update requests.
 [ refresh_interval: <duration> | default = 30s ]