feat: blocking provider mutator (#251)

* introduce wait apis and improve existing tests

Signed-off-by: Kavindu Dodanduwa <[email protected]>

* tests for new apis

Signed-off-by: Kavindu Dodanduwa <[email protected]>

* improve race conditions

Signed-off-by: Kavindu Dodanduwa <[email protected]>

* return error for synchronous provider registrations

Signed-off-by: Kavindu Dodanduwa <[email protected]>

---------

Signed-off-by: Kavindu Dodanduwa <[email protected]>

Author: Kavindu-Dodan

openfeature/api.go

@@ -2,6 +2,7 @@ package openfeature
 
 import (
 	"errors"
+	"fmt"
 	"sync"
 
 	"github.com/go-logr/logr"
@@ -14,7 +15,7 @@ type evaluationAPI struct {
 	defaultProvider FeatureProvider
 	namedProviders  map[string]FeatureProvider
 	hks             []Hook
-	evalCtx         EvaluationContext
+	apiCtx          EvaluationContext
 	logger          logr.Logger
 	mu              sync.RWMutex
 	eventExecutor   *eventExecutor
@@ -28,29 +29,32 @@ func newEvaluationAPI() evaluationAPI {
 		defaultProvider: NoopProvider{},
 		namedProviders:  map[string]FeatureProvider{},
 		hks:             []Hook{},
-		evalCtx:         EvaluationContext{},
+		apiCtx:          EvaluationContext{},
 		logger:          logger,
 		mu:              sync.RWMutex{},
 		eventExecutor:   newEventExecutor(logger),
 	}
 }
 
-// setProvider sets the default FeatureProvider of the evaluationAPI. Returns an error if FeatureProvider is nil
-func (api *evaluationAPI) setProvider(provider FeatureProvider) error {
+// setProvider sets the default FeatureProvider of the evaluationAPI.
+// Returns an error if provider registration cause an error
+func (api *evaluationAPI) setProvider(provider FeatureProvider, async bool) error {
 	api.mu.Lock()
 	defer api.mu.Unlock()
 
 	if provider == nil {
 		return errors.New("default provider cannot be set to nil")
 	}
 
-	// Initialize new default provider and shutdown the old one
-	// Provider update must be non-blocking, hence initialization & shutdown happens concurrently
 	oldProvider := api.defaultProvider
 	api.defaultProvider = provider
 
-	api.initNewAndShutdownOld(provider, oldProvider)
-	err := api.eventExecutor.registerDefaultProvider(provider)
+	err := api.initNewAndShutdownOld(provider, oldProvider, async)
+	if err != nil {
+		return err
+	}
+
+	err = api.eventExecutor.registerDefaultProvider(provider)
 	if err != nil {
 		return err
 	}
@@ -67,7 +71,7 @@ func (api *evaluationAPI) getProvider() FeatureProvider {
 }
 
 // setProvider sets a provider with client name. Returns an error if FeatureProvider is nil
-func (api *evaluationAPI) setNamedProvider(clientName string, provider FeatureProvider) error {
+func (api *evaluationAPI) setNamedProvider(clientName string, provider FeatureProvider, async bool) error {
 	api.mu.Lock()
 	defer api.mu.Unlock()
 
@@ -80,8 +84,12 @@ func (api *evaluationAPI) setNamedProvider(clientName string, provider FeaturePr
 	oldProvider := api.namedProviders[clientName]
 	api.namedProviders[clientName] = provider
 
-	api.initNewAndShutdownOld(provider, oldProvider)
-	err := api.eventExecutor.registerNamedEventingProvider(clientName, provider)
+	err := api.initNewAndShutdownOld(provider, oldProvider, async)
+	if err != nil {
+		return err
+	}
+
+	err = api.eventExecutor.registerNamedEventingProvider(clientName, provider)
 	if err != nil {
 		return err
 	}
@@ -97,11 +105,11 @@ func (api *evaluationAPI) getNamedProviders() map[string]FeatureProvider {
 	return api.namedProviders
 }
 
-func (api *evaluationAPI) setEvaluationContext(evalCtx EvaluationContext) {
+func (api *evaluationAPI) setEvaluationContext(apiCtx EvaluationContext) {
 	api.mu.Lock()
 	defer api.mu.Unlock()
 
-	api.evalCtx = evalCtx
+	api.apiCtx = apiCtx
 }
 
 func (api *evaluationAPI) setLogger(l logr.Logger) {
@@ -163,52 +171,68 @@ func (api *evaluationAPI) forTransaction(clientName string) (FeatureProvider, []
 		provider = api.defaultProvider
 	}
 
-	return provider, api.hks, api.evalCtx
+	return provider, api.hks, api.apiCtx
 }
 
 // initNewAndShutdownOld is a helper to initialise new FeatureProvider and shutdown the old FeatureProvider.
-// Operations happen concurrently.
-func (api *evaluationAPI) initNewAndShutdownOld(newProvider FeatureProvider, oldProvider FeatureProvider) {
-	v, ok := newProvider.(StateHandler)
-	if ok && v.Status() == NotReadyState {
-		go func(provider FeatureProvider, stateHandler StateHandler, evalCtx EvaluationContext, eventChan chan eventPayload) {
-			err := stateHandler.Init(evalCtx)
-			// emit ready/error event once initialization is complete
-			if err != nil {
-				eventChan <- eventPayload{
-					Event{
-						ProviderName:         provider.Metadata().Name,
-						EventType:            ProviderError,
-						ProviderEventDetails: ProviderEventDetails{},
-					}, provider,
-				}
-			} else {
-				eventChan <- eventPayload{
-					Event{
-						ProviderName:         provider.Metadata().Name,
-						EventType:            ProviderReady,
-						ProviderEventDetails: ProviderEventDetails{},
-					}, provider,
-				}
-			}
-		}(newProvider, v, api.evalCtx, api.eventExecutor.eventChan)
-	}
-
-	v, ok = oldProvider.(StateHandler)
+func (api *evaluationAPI) initNewAndShutdownOld(newProvider FeatureProvider, oldProvider FeatureProvider, async bool) error {
+	if async {
+		go func(executor *eventExecutor, ctx EvaluationContext) {
+			// for async initialization, error is conveyed as an event
+			event, _ := initializer(newProvider, ctx)
+			executor.triggerEvent(event, newProvider)
+		}(api.eventExecutor, api.apiCtx)
+	} else {
+		event, err := initializer(newProvider, api.apiCtx)
+		api.eventExecutor.triggerEvent(event, newProvider)
+		if err != nil {
+			return err
+		}
+	}
+
+	v, ok := oldProvider.(StateHandler)
 
 	// oldProvider can be nil or without state handling capability
 	if oldProvider == nil || !ok {
-		return
+		return nil
 	}
 
 	// check for multiple bindings
 	if oldProvider == api.defaultProvider || contains(oldProvider, maps.Values(api.namedProviders)) {
-		return
+		return nil
 	}
 
 	go func(forShutdown StateHandler) {
 		forShutdown.Shutdown()
 	}(v)
+
+	return nil
+}
+
+// initializer is a helper to execute provider initialization and generate appropriate event for the initialization
+// It also returns an error if the initialization resulted in an error
+func initializer(provider FeatureProvider, apiCtx EvaluationContext) (Event, error) {
+	var event = Event{
+		ProviderName: provider.Metadata().Name,
+		EventType:    ProviderReady,
+		ProviderEventDetails: ProviderEventDetails{
+			Message: "Provider initialization successful",
+		},
+	}
+
+	handler, ok := provider.(StateHandler)
+	if !ok {
+		// Note - a provider without state handling capability can be assumed to be ready immediately.
+		return event, nil
+	}
+
+	err := handler.Init(apiCtx)
+	if err != nil {
+		event.EventType = ProviderError
+		event.Message = fmt.Sprintf("Provider initialization error, %v", err)
+	}
+
+	return event, err
 }
 
 func contains(provider FeatureProvider, in []FeatureProvider) bool {

openfeature/event_executor.go

@@ -327,7 +327,7 @@ func (e *eventExecutor) triggerEvent(event Event, handler FeatureProvider) {
 		}
 	}
 
-	if e.defaultProviderReference.featureProvider != handler {
+	if !reflect.DeepEqual(e.defaultProviderReference.featureProvider, handler) {
 		return
 	}
 

openfeature/event_executor_test.go

@@ -82,7 +82,8 @@ func TestEventHandler_Eventing(t *testing.T) {
 			rsp <- details
 		}
 
-		AddHandler(ProviderReady, &callBack)
+		eventType := ProviderConfigChange
+		AddHandler(eventType, &callBack)
 
 		fCh := []string{"flagA"}
 		meta := map[string]interface{}{
@@ -91,7 +92,7 @@ func TestEventHandler_Eventing(t *testing.T) {
 
 		// trigger event from provider implementation
 		eventingImpl.Invoke(Event{
-			EventType: ProviderReady,
+			EventType: eventType,
 			ProviderEventDetails: ProviderEventDetails{
 				Message:       "ReadyMessage",
 				FlagChanges:   fCh,
@@ -139,7 +140,7 @@ func TestEventHandler_Eventing(t *testing.T) {
 		// associated to client name
 		associatedName := "providerForClient"
 
-		err := SetNamedProvider(associatedName, eventingProvider)
+		err := SetNamedProviderAndWait(associatedName, eventingProvider)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -214,13 +215,13 @@ func TestEventHandler_clientAssociation(t *testing.T) {
 	}
 
 	// default provider
-	err := SetProvider(defaultProvider)
+	err := SetProviderAndWait(defaultProvider)
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	// named provider(associated to name someClient)
-	err = SetNamedProvider("someClient", struct {
+	err = SetNamedProviderAndWait("someClient", struct {
 		FeatureProvider
 		EventHandler
 	}{
@@ -273,7 +274,7 @@ func TestEventHandler_ErrorHandling(t *testing.T) {
 		eventing,
 	}
 
-	errorCallback := func(e EventDetails) {
+	failingCallback := func(e EventDetails) {
 		panic("callback panic")
 	}
 
@@ -292,24 +293,26 @@ func TestEventHandler_ErrorHandling(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	successEventType := ProviderStale
+
 	// api level handlers
-	AddHandler(ProviderReady, &errorCallback)
-	AddHandler(ProviderReady, &successAPICallback)
+	AddHandler(ProviderConfigChange, &failingCallback)
+	AddHandler(successEventType, &successAPICallback)
 
 	// provider association
 	providerName := "providerA"
 
 	client := NewClient(providerName)
 
 	// client level handlers
-	client.AddHandler(ProviderReady, &errorCallback)
-	client.AddHandler(ProviderReady, &successClientCallback)
+	client.AddHandler(ProviderConfigChange, &failingCallback)
+	client.AddHandler(successEventType, &successClientCallback)
 
 	// trigger events manually
 	go func() {
 		eventing.Invoke(Event{
 			ProviderName:         providerName,
-			EventType:            ProviderReady,
+			EventType:            successEventType,
 			ProviderEventDetails: ProviderEventDetails{},
 		})
 	}()
@@ -967,7 +970,7 @@ func TestEventHandler_HandlersRunImmediately(t *testing.T) {
 			},
 		}
 
-		if err := SetProvider(provider); err != nil {
+		if err := SetProviderAndWait(provider); err != nil {
 			t.Fatal(err)
 		}
 
@@ -1001,7 +1004,7 @@ func TestEventHandler_HandlersRunImmediately(t *testing.T) {
 			},
 		}
 
-		if err := SetProvider(provider); err != nil {
+		if err := SetProviderAndWait(provider); err != nil {
 			t.Fatal(err)
 		}
 

openfeature/openfeature.go

@@ -20,13 +20,25 @@ func initSingleton() {
 // SetProvider sets the default provider. Provider initialization is asynchronous and status can be checked from
 // provider status
 func SetProvider(provider FeatureProvider) error {
-	return api.setProvider(provider)
+	return api.setProvider(provider, true)
+}
+
+// SetProviderAndWait sets the default provider and waits for its initialization.
+// Returns an error if initialization cause error
+func SetProviderAndWait(provider FeatureProvider) error {
+	return api.setProvider(provider, false)
 }
 
 // SetNamedProvider sets a provider mapped to the given Client name. Provider initialization is asynchronous and
 // status can be checked from provider status
 func SetNamedProvider(clientName string, provider FeatureProvider) error {
-	return api.setNamedProvider(clientName, provider)
+	return api.setNamedProvider(clientName, provider, true)
+}
+
+// SetNamedProviderAndWait sets a provider mapped to the given Client name and waits for its initialization.
+// Returns an error if initialization cause error
+func SetNamedProviderAndWait(clientName string, provider FeatureProvider) error {
+	return api.setNamedProvider(clientName, provider, false)
 }
 
 // SetEvaluationContext sets the global evaluation context.