receiver_creator: lookup configured observer extensions (#179)

This utilizes `host.GetExtensions` to find observers that have been configured
using `watch_observers`. receiver_creator can be configured to watch zero or
more observers. To support this the receiver templates have been moved under
"receivers" key to be able to differentiate subreceiver config keys from config
keys for the receiver_creator itself.

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/open-telemetry/opentelemetry-collector-contrib/exporter/sapmexporter v0.0.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/exporter/signalfxexporter v0.0.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/exporter/stackdriverexporter v0.0.0
+	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer v0.0.0-20200417175348-2f20d0c404f4 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/processor/k8sprocessor v0.0.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/carbonreceiver v0.0.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/collectdreceiver v0.0.0

go.sum

@@ -935,6 +935,8 @@ github.com/onsi/gomega v1.9.0 h1:R1uwffexN6Pr340GtYRIdZmAiN4J+iw6WG4wog1DUXg=
 github.com/onsi/gomega v1.9.0/go.mod h1:Ho0h+IUsWyvy1OpqCwxlQ/21gkhVunqlU8fDGcoTdcA=
 github.com/open-telemetry/opentelemetry-collector v0.3.1-0.20200414190247-75ae9198a89e h1:w67eqMTZ7ggKmTJDV3+ertwhWpmPltreRMZ6+DRKk98=
 github.com/open-telemetry/opentelemetry-collector v0.3.1-0.20200414190247-75ae9198a89e/go.mod h1:aZAL+YwTtk+1YkTj8dDgTvv06dU8twzOdRowRtBfEKo=
+github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer v0.0.0-20200417175348-2f20d0c404f4 h1:PZFHe3iV5eO1ODxpFi7WYYprnsqe1sdK5GiuRRLOaBc=
+github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer v0.0.0-20200417175348-2f20d0c404f4/go.mod h1:0CKaqU1lHv0dWPhVSXDprfZ8vjBhxXJjXMUYIBU/0zQ=
 github.com/open-telemetry/opentelemetry-proto v0.3.0 h1:+ASAtcayvoELyCF40+rdCMlBOhZIn5TPDez85zSYc30=
 github.com/open-telemetry/opentelemetry-proto v0.3.0/go.mod h1:PMR5GI0F7BSpio+rBGFxNm6SLzg3FypDTcFuQZnO+F8=
 github.com/opencontainers/go-digest v1.0.0-rc1/go.mod h1:cMLVZDEM3+U2I4VmLI6N8jQYUd2OVphdqWwCJHrFt2s=

receiver/receivercreator/README.md

@@ -1,17 +1,28 @@
 # receiver_creator
 
-This receiver can instantiate other receivers at runtime.
+This receiver can instantiate other receivers at runtime based on whether observed endpoints match a configured rule.
 
-TODO: More after it can react to observer events.
+## TODO
+* Observer endpoint details
+* Rule matching
 
 ## Example
 ```yaml
+extensions:
+  # Configures the Kubernetes observer to watch for pod start and stop events.
+  k8s_observer:
+
 receivers:
   receiver_creator/1:
-    examplereceiver/1:
-      rule: <TODO>
-      config:
-        endpoint: localhost:12345
+    # Name of the extensions to watch for endpoints to start and stop.
+    watch_observers: [k8s_observer]
+    receivers:
+        redis/1:
+          # If this rule matches an instance of this receiver will be started.
+          rule: port == 6379
+          config:
+            # Static receiver-specific config.
+            password: secret
 
 processors:
   exampleprocessor:

receiver/receivercreator/config.go

@@ -15,8 +15,21 @@
 package receivercreator
 
 import (
+	"reflect"
+
 	otelconfig "github.com/open-telemetry/opentelemetry-collector/config"
 	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
+	"github.com/spf13/cast"
+	"github.com/spf13/viper"
+)
+
+const (
+	// receiversConfigKey is the config key name used to specify the subreceivers.
+	receiversConfigKey = "receivers"
+	// endpointConfigKey is the key name mapping to ReceiverSettings.Endpoint.
+	endpointConfigKey = "endpoint"
+	// configKey is the key name in a subreceiver.
+	configKey = "config"
 )
 
 // receiverConfig describes a receiver instance with a default config.
@@ -63,4 +76,22 @@ func newReceiverTemplate(name string, config userConfigMap) (receiverTemplate, e
 type Config struct {
 	configmodels.ReceiverSettings `mapstructure:",squash"`
 	receiverTemplates             map[string]receiverTemplate
+	// WatchObservers are the extensions to listen to endpoints from.
+	WatchObservers []string `mapstructure:"watch_observers"`
+}
+
+// Copied from the Viper but changed to use the same delimiter.
+// See https://github.com/spf13/viper/issues/871
+func viperSub(v *viper.Viper, key string) *viper.Viper {
+	subv := otelconfig.NewViper()
+	data := v.Get(key)
+	if data == nil {
+		return subv
+	}
+
+	if reflect.TypeOf(data).Kind() == reflect.Map {
+		subv.MergeConfigMap(cast.ToStringMap(data))
+		return subv
+	}
+	return subv
 }

receiver/receivercreator/config_test.go

@@ -28,7 +28,8 @@ import (
 
 type mockHostFactories struct {
 	componenttest.NopHost
-	factories config.Factories
+	factories  config.Factories
+	extensions map[configmodels.Extension]component.ServiceExtension
 }
 
 // GetFactory of the specified kind. Returns the factory for a component type.
@@ -46,7 +47,11 @@ func (mh *mockHostFactories) GetFactory(kind component.Kind, componentType strin
 	return nil
 }
 
-func exampleCreatorFactory(t *testing.T) (component.Host, *configmodels.Config) {
+func (mh *mockHostFactories) GetExtensions() map[configmodels.Extension]component.ServiceExtension {
+	return mh.extensions
+}
+
+func exampleCreatorFactory(t *testing.T) (*mockHostFactories, *configmodels.Config) {
 	factories, err := config.ExampleComponents()
 	require.Nil(t, err)
 
@@ -80,4 +85,5 @@ func TestLoadConfig(t *testing.T) {
 	assert.Equal(t, userConfigMap{
 		endpointConfigKey: "localhost:12345",
 	}, r1.receiverTemplates["examplereceiver/1"].config)
+	assert.Equal(t, []string{"mock_observer"}, r1.WatchObservers)
 }

receiver/receivercreator/factory.go

@@ -52,17 +52,22 @@ func (f *Factory) CustomUnmarshaler() component.CustomUnmarshaler {
 		}
 		c := intoCfg.(*Config)
 
-		// TODO: Change the sub-receivers to be under "receivers" to allow other config for the main receiver-creator receiver.
-		for subreceiverKey := range sourceViperSection.AllSettings() {
-			cfgSection := sourceViperSection.GetStringMap(subreceiverKey + "::config")
+		if err := sourceViperSection.Unmarshal(&c); err != nil {
+			return err
+		}
+
+		receiversCfg := viperSub(sourceViperSection, receiversConfigKey)
+
+		for subreceiverKey := range receiversCfg.AllSettings() {
+			cfgSection := viperSub(receiversCfg, subreceiverKey).GetStringMap(configKey)
 			subreceiver, err := newReceiverTemplate(subreceiverKey, cfgSection)
 			if err != nil {
 				return err
 			}
 
 			// Unmarshals receiver_creator configuration like rule.
 			// TODO: validate discovery rule
-			if err := sourceViperSection.UnmarshalKey(subreceiverKey, &subreceiver); err != nil {
+			if err := receiversCfg.UnmarshalKey(subreceiverKey, &subreceiver); err != nil {
 				return fmt.Errorf("failed to deserialize sub-receiver %q: %s", subreceiverKey, err)
 			}
 

receiver/receivercreator/go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/census-instrumentation/opencensus-proto v0.2.1
 	github.com/open-telemetry/opentelemetry-collector v0.3.1-0.20200414190247-75ae9198a89e
 	github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer v0.0.0
+	github.com/spf13/cast v1.3.1
 	github.com/spf13/viper v1.6.2
 	github.com/stretchr/testify v1.4.0
 	go.uber.org/zap v1.13.0

receiver/receivercreator/receiver.go

@@ -17,6 +17,7 @@ package receivercreator
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	"github.com/open-telemetry/opentelemetry-collector/component"
 	"github.com/open-telemetry/opentelemetry-collector/consumer"
@@ -25,9 +26,6 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/observer"
 )
 
-// endpointConfigKey is the key name mapping to ReceiverSettings.Endpoint.
-const endpointConfigKey = "endpoint"
-
 var (
 	errNilNextConsumer = errors.New("nil nextConsumer")
 )
@@ -40,7 +38,6 @@ type receiverCreator struct {
 	logger          *zap.Logger
 	cfg             *Config
 	observerHandler observerHandler
-	observer        observer.Observable
 }
 
 // newReceiverCreator creates the receiver_creator with the given parameters.
@@ -86,7 +83,39 @@ func (rc *receiverCreator) Start(ctx context.Context, host component.Host) error
 			host: &loggingHost{host, rc.logger},
 		}}
 
-	rc.observer.ListAndWatch(&rc.observerHandler)
+	observers := map[string]observer.Observable{}
+
+	// Match all configured observers to the extensions that are running.
+	for _, watchObserver := range rc.cfg.WatchObservers {
+		for cfg, ext := range host.GetExtensions() {
+			if cfg.Type() != watchObserver {
+				continue
+			}
+
+			obs, ok := ext.(observer.Observable)
+			if !ok {
+				return fmt.Errorf("extension %q in watch_observers is not an observer", watchObserver)
+			}
+			observers[watchObserver] = obs
+		}
+	}
+
+	// Make sure all observers are present before starting any.
+	for _, watchObserver := range rc.cfg.WatchObservers {
+		if observers[watchObserver] == nil {
+			return fmt.Errorf("failed to find observer %q in the extensions list", watchObserver)
+		}
+	}
+
+	if len(observers) == 0 {
+		rc.logger.Warn("no observers were configured and no subreceivers will be started. receiver_creator will be disabled",
+			zap.String("receiver", rc.cfg.Name()))
+	}
+
+	// Start all configured watchers.
+	for _, observable := range observers {
+		observable.ListAndWatch(&rc.observerHandler)
+	}
 
 	return nil
 }

receiver/receivercreator/receiver_test.go

@@ -24,9 +24,11 @@ import (
 	commonpb "github.com/census-instrumentation/opencensus-proto/gen-go/agent/common/v1"
 	metricspb "github.com/census-instrumentation/opencensus-proto/gen-go/metrics/v1"
 	resourcepb "github.com/census-instrumentation/opencensus-proto/gen-go/resource/v1"
+	"github.com/open-telemetry/opentelemetry-collector/component"
 	"github.com/open-telemetry/opentelemetry-collector/component/componenttest"
 	"github.com/open-telemetry/opentelemetry-collector/config"
 	"github.com/open-telemetry/opentelemetry-collector/config/configcheck"
+	"github.com/open-telemetry/opentelemetry-collector/config/configmodels"
 	"github.com/open-telemetry/opentelemetry-collector/consumer"
 	"github.com/open-telemetry/opentelemetry-collector/consumer/consumerdata"
 	"github.com/stretchr/testify/assert"
@@ -60,6 +62,16 @@ func (p *mockMetricsConsumer) ConsumeMetricsData(ctx context.Context, md consume
 type mockObserver struct {
 }
 
+func (m *mockObserver) Start(ctx context.Context, host component.Host) error {
+	return nil
+}
+
+func (m *mockObserver) Shutdown(ctx context.Context) error {
+	return nil
+}
+
+var _ component.ServiceExtension = (*mockObserver)(nil)
+
 func (m *mockObserver) ListAndWatch(notify observer.Notify) {
 	notify.OnAdd([]observer.Endpoint{observer.NewHostEndpoint("foobar", "169.168.1.100", nil)})
 }
@@ -68,13 +80,18 @@ var _ observer.Observable = (*mockObserver)(nil)
 
 func TestMockedEndToEnd(t *testing.T) {
 	host, cfg := exampleCreatorFactory(t)
+	host.extensions = map[configmodels.Extension]component.ServiceExtension{
+		&configmodels.ExtensionSettings{
+			TypeVal: "mock_observer",
+			NameVal: "mock_observer",
+		}: &mockObserver{},
+	}
 	dynCfg := cfg.Receivers["receiver_creator/1"]
 	factory := &Factory{}
 	mockConsumer := &mockMetricsConsumer{}
 	rcvr, err := factory.CreateMetricsReceiver(zap.NewNop(), dynCfg, mockConsumer)
 	require.NoError(t, err)
 	dyn := rcvr.(*receiverCreator)
-	dyn.observer = &mockObserver{}
 	require.NoError(t, rcvr.Start(context.Background(), host))
 
 	var shutdownOnce sync.Once

receiver/receivercreator/testdata/config.yaml

@@ -1,10 +1,12 @@
 receivers:
   receiver_creator:
   receiver_creator/1:
-    examplereceiver/1:
-      rule: enabled
-      config:
-        endpoint: localhost:12345
+    watch_observers: [mock_observer]
+    receivers:
+      examplereceiver/1:
+        rule: enabled
+        config:
+          endpoint: localhost:12345
 
 processors:
   exampleprocessor: