abstract out eventing logic

Signed-off-by: Kavindu Dodanduwa <kavindudodanduwa@gmail.com>

core/pkg/service/flag-evaluation/connect_service.go

@@ -94,11 +94,7 @@ func (s *ConnectService) Serve(ctx context.Context, svcConf service.Configuratio
 
 // Notify emits change event notifications for subscriptions
 func (s *ConnectService) Notify(n service.Notification) {
-	s.eventingConfiguration.mu.RLock()
-	defer s.eventingConfiguration.mu.RUnlock()
-	for _, send := range s.eventingConfiguration.subs {
-		send <- n
-	}
+	s.eventingConfiguration.emitToAll(n)
 }
 
 func (s *ConnectService) setupServer(svcConf service.Configuration) (net.Listener, error) {

core/pkg/service/flag-evaluation/eventing.go

@@ -0,0 +1,36 @@
+package service
+
+import (
+	"sync"
+
+	iservice "github.com/open-feature/flagd/core/pkg/service"
+)
+
+// eventingConfiguration is a wrapper for notification subscriptions
+type eventingConfiguration struct {
+	mu   *sync.RWMutex
+	subs map[interface{}]chan iservice.Notification
+}
+
+func (eventing *eventingConfiguration) subscribe(id interface{}, notifyChan chan iservice.Notification) {
+	eventing.mu.Lock()
+	defer eventing.mu.Unlock()
+
+	eventing.subs[id] = notifyChan
+}
+
+func (eventing *eventingConfiguration) emitToAll(n iservice.Notification) {
+	eventing.mu.RLock()
+	defer eventing.mu.RUnlock()
+
+	for _, send := range eventing.subs {
+		send <- n
+	}
+}
+
+func (eventing *eventingConfiguration) unSubscribe(id interface{}) {
+	eventing.mu.Lock()
+	defer eventing.mu.Unlock()
+
+	delete(eventing.subs, id)
+}

core/pkg/service/flag-evaluation/eventing_test.go

@@ -0,0 +1,55 @@
+package service
+
+import (
+	"sync"
+	"testing"
+
+	iservice "github.com/open-feature/flagd/core/pkg/service"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSubscribe(t *testing.T) {
+	// given
+	eventing := &eventingConfiguration{
+		subs: make(map[interface{}]chan iservice.Notification),
+		mu:   &sync.RWMutex{},
+	}
+
+	idA := "a"
+	chanA := make(chan iservice.Notification, 1)
+
+	idB := "b"
+	chanB := make(chan iservice.Notification, 1)
+
+	// when
+	eventing.subscribe(idA, chanA)
+	eventing.subscribe(idB, chanB)
+
+	// then
+	require.Equal(t, chanA, eventing.subs[idA], "incorrect subscription association")
+	require.Equal(t, chanB, eventing.subs[idB], "incorrect subscription association")
+}
+
+func TestUnsubscribe(t *testing.T) {
+	// given
+	eventing := &eventingConfiguration{
+		subs: make(map[interface{}]chan iservice.Notification),
+		mu:   &sync.RWMutex{},
+	}
+
+	idA := "a"
+	chanA := make(chan iservice.Notification, 1)
+	idB := "b"
+	chanB := make(chan iservice.Notification, 1)
+
+	// when
+	eventing.subscribe(idA, chanA)
+	eventing.subscribe(idB, chanB)
+
+	eventing.unSubscribe(idA)
+
+	// then
+	require.Empty(t, eventing.subs[idA],
+		"expected subscription cleared, but value present: %v", eventing.subs[idA])
+	require.Equal(t, chanB, eventing.subs[idB], "incorrect subscription association")
+}

core/pkg/service/flag-evaluation/flag_evaluator.go

@@ -3,7 +3,6 @@ package service
 import (
 	"context"
 	"fmt"
-	"sync"
 	"time"
 
 	schemaV1 "buf.build/gen/go/open-feature/flagd/protocolbuffers/go/schema/v1"
@@ -25,11 +24,6 @@ type FlagEvaluationService struct {
 	eventingConfiguration *eventingConfiguration
 }
 
-type eventingConfiguration struct {
-	mu   *sync.RWMutex
-	subs map[interface{}]chan service.Notification
-}
-
 // NewFlagEvaluationService creates a FlagEvaluationService with provided parameters
 func NewFlagEvaluationService(log *logger.Logger,
 	eval eval.IEvaluator, eventingCfg *eventingConfiguration, metricsRecorder *telemetry.MetricsRecorder,
@@ -104,13 +98,9 @@ func (s *FlagEvaluationService) EventStream(
 	stream *connect.ServerStream[schemaV1.EventStreamResponse],
 ) error {
 	requestNotificationChan := make(chan service.Notification, 1)
-	s.eventingConfiguration.mu.Lock()
-	s.eventingConfiguration.subs[req] = requestNotificationChan
-	s.eventingConfiguration.mu.Unlock()
+	s.eventingConfiguration.subscribe(req, requestNotificationChan)
 	defer func() {
-		s.eventingConfiguration.mu.Lock()
-		delete(s.eventingConfiguration.subs, req)
-		s.eventingConfiguration.mu.Unlock()
+		s.eventingConfiguration.unSubscribe(req)
 	}()
 	requestNotificationChan <- service.Notification{
 		Type: service.ProviderReady,