feat!: support emitting errors from the bulk evaluator (#1338)

Fixes #1328

### Improvement

flagd's core components are intended to be reused. This PR change
the`IStore` interface by allowing an error to be returned from `GetAll`.
This error is then propagated through `ResolveAllValues`. This change
enables custom `IStore` implementations to return errors and propagate
them through the resolver layer.

With this change, I have upgrade OFREP bulk evaluator and flagd RPC
`ResolveAll` with error propagation.

OFREP - Log warning with resolver error and return HTTP 500 with a
tracking reference
RPC - Log warning with resolver error and return an error with a
tracking reference

Signed-off-by: Kavindu Dodanduwa <kavindudodanduwa@gmail.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>

core/pkg/evaluator/fractional.go

@@ -40,7 +40,7 @@ func NewFractional(logger *logger.Logger) *Fractional {
 func (fe *Fractional) Evaluate(values, data any) any {
 	valueToDistribute, feDistributions, err := parseFractionalEvaluationData(values, data)
 	if err != nil {
-		fe.Logger.Error(fmt.Sprintf("parse fractional evaluation data: %v", err))
+		fe.Logger.Warn(fmt.Sprintf("parse fractional evaluation data: %v", err))
 		return nil
 	}
 

core/pkg/evaluator/ievaluator.go

@@ -77,5 +77,5 @@ type IResolver interface {
 	ResolveAllValues(
 		ctx context.Context,
 		reqID string,
-		context map[string]any) (values []AnyValue)
+		context map[string]any) (values []AnyValue, err error)
 }

core/pkg/evaluator/json.go

@@ -156,17 +156,22 @@ func NewResolver(store store.IStore, logger *logger.Logger, jsonEvalTracer trace
 	return Resolver{store: store, Logger: logger, tracer: jsonEvalTracer}
 }
 
-func (je *Resolver) ResolveAllValues(ctx context.Context, reqID string, context map[string]any) []AnyValue {
+func (je *Resolver) ResolveAllValues(ctx context.Context, reqID string, context map[string]any) ([]AnyValue, error) {
 	_, span := je.tracer.Start(ctx, "resolveAll")
 	defer span.End()
 
+	var err error
+	allFlags, err := je.store.GetAll(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("error retreiving flags from the store: %w", err)
+	}
+
 	values := []AnyValue{}
 	var value interface{}
 	var variant string
 	var reason string
 	var metadata map[string]interface{}
-	var err error
-	allFlags := je.store.GetAll(ctx)
+
 	for flagKey, flag := range allFlags {
 		if flag.State == Disabled {
 			// ignore evaluation of disabled flag
@@ -176,44 +181,21 @@ func (je *Resolver) ResolveAllValues(ctx context.Context, reqID string, context
 		defaultValue := flag.Variants[flag.DefaultVariant]
 		switch defaultValue.(type) {
 		case bool:
-			value, variant, reason, metadata, err = resolve[bool](
-				ctx,
-				reqID,
-				flagKey,
-				context,
-				je.evaluateVariant,
-			)
+			value, variant, reason, metadata, err = resolve[bool](ctx, reqID, flagKey, context, je.evaluateVariant)
 		case string:
-			value, variant, reason, metadata, err = resolve[string](
-				ctx,
-				reqID,
-				flagKey,
-				context,
-				je.evaluateVariant,
-			)
+			value, variant, reason, metadata, err = resolve[string](ctx, reqID, flagKey, context, je.evaluateVariant)
 		case float64:
-			value, variant, reason, metadata, err = resolve[float64](
-				ctx,
-				reqID,
-				flagKey,
-				context,
-				je.evaluateVariant,
-			)
+			value, variant, reason, metadata, err = resolve[float64](ctx, reqID, flagKey, context, je.evaluateVariant)
 		case map[string]any:
-			value, variant, reason, metadata, err = resolve[map[string]any](
-				ctx,
-				reqID,
-				flagKey,
-				context,
-				je.evaluateVariant,
-			)
+			value, variant, reason, metadata, err = resolve[map[string]any](ctx, reqID, flagKey, context, je.evaluateVariant)
 		}
 		if err != nil {
 			je.Logger.ErrorWithID(reqID, fmt.Sprintf("bulk evaluation: key: %s returned error: %s", flagKey, err.Error()))
 		}
 		values = append(values, NewAnyValue(value, variant, reason, flagKey, metadata, err))
 	}
-	return values
+
+	return values, nil
 }
 
 func (je *Resolver) ResolveBooleanValue(

core/pkg/evaluator/json_test.go

@@ -335,7 +335,11 @@ func TestResolveAllValues(t *testing.T) {
 	}
 	const reqID = "default"
 	for _, test := range tests {
-		vals := evaluator.ResolveAllValues(context.TODO(), reqID, test.context)
+		vals, err := evaluator.ResolveAllValues(context.TODO(), reqID, test.context)
+		if err != nil {
+			t.Error("error from resolver", err)
+		}
+
 		for _, val := range vals {
 			// disabled flag must be ignored from bulk evaluation
 			if val.FlagKey == DisabledFlag {
@@ -1234,21 +1238,30 @@ func TestFlagStateSafeForConcurrentReadWrites(t *testing.T) {
 		"Add_ResolveAllValues": {
 			dataSyncType: sync.ADD,
 			flagResolution: func(evaluator *evaluator.JSON) error {
-				evaluator.ResolveAllValues(context.TODO(), "", nil)
+				_, err := evaluator.ResolveAllValues(context.TODO(), "", nil)
+				if err != nil {
+					return err
+				}
 				return nil
 			},
 		},
 		"Update_ResolveAllValues": {
 			dataSyncType: sync.UPDATE,
 			flagResolution: func(evaluator *evaluator.JSON) error {
-				evaluator.ResolveAllValues(context.TODO(), "", nil)
+				_, err := evaluator.ResolveAllValues(context.TODO(), "", nil)
+				if err != nil {
+					return err
+				}
 				return nil
 			},
 		},
 		"Delete_ResolveAllValues": {
 			dataSyncType: sync.DELETE,
 			flagResolution: func(evaluator *evaluator.JSON) error {
-				evaluator.ResolveAllValues(context.TODO(), "", nil)
+				_, err := evaluator.ResolveAllValues(context.TODO(), "", nil)
+				if err != nil {
+					return err
+				}
 				return nil
 			},
 		},

core/pkg/evaluator/mock/ievaluator.go

@@ -57,11 +57,12 @@ func (mr *MockIEvaluatorMockRecorder) GetState() *gomock.Call {
 }
 
 // ResolveAllValues mocks base method.
-func (m *MockIEvaluator) ResolveAllValues(ctx context.Context, reqID string, context map[string]any) []evaluator.AnyValue {
+func (m *MockIEvaluator) ResolveAllValues(ctx context.Context, reqID string, context map[string]any) ([]evaluator.AnyValue, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "ResolveAllValues", ctx, reqID, context)
 	ret0, _ := ret[0].([]evaluator.AnyValue)
-	return ret0
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
 }
 
 // ResolveAllValues indicates an expected call of ResolveAllValues.
@@ -189,3 +190,145 @@ func (mr *MockIEvaluatorMockRecorder) SetState(payload any) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SetState", reflect.TypeOf((*MockIEvaluator)(nil).SetState), payload)
 }
+
+// MockIResolver is a mock of IResolver interface.
+type MockIResolver struct {
+	ctrl     *gomock.Controller
+	recorder *MockIResolverMockRecorder
+}
+
+// MockIResolverMockRecorder is the mock recorder for MockIResolver.
+type MockIResolverMockRecorder struct {
+	mock *MockIResolver
+}
+
+// NewMockIResolver creates a new mock instance.
+func NewMockIResolver(ctrl *gomock.Controller) *MockIResolver {
+	mock := &MockIResolver{ctrl: ctrl}
+	mock.recorder = &MockIResolverMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockIResolver) EXPECT() *MockIResolverMockRecorder {
+	return m.recorder
+}
+
+// ResolveAllValues mocks base method.
+func (m *MockIResolver) ResolveAllValues(ctx context.Context, reqID string, context map[string]any) ([]evaluator.AnyValue, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveAllValues", ctx, reqID, context)
+	ret0, _ := ret[0].([]evaluator.AnyValue)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// ResolveAllValues indicates an expected call of ResolveAllValues.
+func (mr *MockIResolverMockRecorder) ResolveAllValues(ctx, reqID, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveAllValues", reflect.TypeOf((*MockIResolver)(nil).ResolveAllValues), ctx, reqID, context)
+}
+
+// ResolveAsAnyValue mocks base method.
+func (m *MockIResolver) ResolveAsAnyValue(ctx context.Context, reqID, flagKey string, context map[string]any) evaluator.AnyValue {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveAsAnyValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(evaluator.AnyValue)
+	return ret0
+}
+
+// ResolveAsAnyValue indicates an expected call of ResolveAsAnyValue.
+func (mr *MockIResolverMockRecorder) ResolveAsAnyValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveAsAnyValue", reflect.TypeOf((*MockIResolver)(nil).ResolveAsAnyValue), ctx, reqID, flagKey, context)
+}
+
+// ResolveBooleanValue mocks base method.
+func (m *MockIResolver) ResolveBooleanValue(ctx context.Context, reqID, flagKey string, context map[string]any) (bool, string, string, map[string]any, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveBooleanValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(bool)
+	ret1, _ := ret[1].(string)
+	ret2, _ := ret[2].(string)
+	ret3, _ := ret[3].(map[string]any)
+	ret4, _ := ret[4].(error)
+	return ret0, ret1, ret2, ret3, ret4
+}
+
+// ResolveBooleanValue indicates an expected call of ResolveBooleanValue.
+func (mr *MockIResolverMockRecorder) ResolveBooleanValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveBooleanValue", reflect.TypeOf((*MockIResolver)(nil).ResolveBooleanValue), ctx, reqID, flagKey, context)
+}
+
+// ResolveFloatValue mocks base method.
+func (m *MockIResolver) ResolveFloatValue(ctx context.Context, reqID, flagKey string, context map[string]any) (float64, string, string, map[string]any, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveFloatValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(float64)
+	ret1, _ := ret[1].(string)
+	ret2, _ := ret[2].(string)
+	ret3, _ := ret[3].(map[string]any)
+	ret4, _ := ret[4].(error)
+	return ret0, ret1, ret2, ret3, ret4
+}
+
+// ResolveFloatValue indicates an expected call of ResolveFloatValue.
+func (mr *MockIResolverMockRecorder) ResolveFloatValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveFloatValue", reflect.TypeOf((*MockIResolver)(nil).ResolveFloatValue), ctx, reqID, flagKey, context)
+}
+
+// ResolveIntValue mocks base method.
+func (m *MockIResolver) ResolveIntValue(ctx context.Context, reqID, flagKey string, context map[string]any) (int64, string, string, map[string]any, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveIntValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(int64)
+	ret1, _ := ret[1].(string)
+	ret2, _ := ret[2].(string)
+	ret3, _ := ret[3].(map[string]any)
+	ret4, _ := ret[4].(error)
+	return ret0, ret1, ret2, ret3, ret4
+}
+
+// ResolveIntValue indicates an expected call of ResolveIntValue.
+func (mr *MockIResolverMockRecorder) ResolveIntValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveIntValue", reflect.TypeOf((*MockIResolver)(nil).ResolveIntValue), ctx, reqID, flagKey, context)
+}
+
+// ResolveObjectValue mocks base method.
+func (m *MockIResolver) ResolveObjectValue(ctx context.Context, reqID, flagKey string, context map[string]any) (map[string]any, string, string, map[string]any, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveObjectValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(map[string]any)
+	ret1, _ := ret[1].(string)
+	ret2, _ := ret[2].(string)
+	ret3, _ := ret[3].(map[string]any)
+	ret4, _ := ret[4].(error)
+	return ret0, ret1, ret2, ret3, ret4
+}
+
+// ResolveObjectValue indicates an expected call of ResolveObjectValue.
+func (mr *MockIResolverMockRecorder) ResolveObjectValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveObjectValue", reflect.TypeOf((*MockIResolver)(nil).ResolveObjectValue), ctx, reqID, flagKey, context)
+}
+
+// ResolveStringValue mocks base method.
+func (m *MockIResolver) ResolveStringValue(ctx context.Context, reqID, flagKey string, context map[string]any) (string, string, string, map[string]any, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ResolveStringValue", ctx, reqID, flagKey, context)
+	ret0, _ := ret[0].(string)
+	ret1, _ := ret[1].(string)
+	ret2, _ := ret[2].(string)
+	ret3, _ := ret[3].(map[string]any)
+	ret4, _ := ret[4].(error)
+	return ret0, ret1, ret2, ret3, ret4
+}
+
+// ResolveStringValue indicates an expected call of ResolveStringValue.
+func (mr *MockIResolverMockRecorder) ResolveStringValue(ctx, reqID, flagKey, context any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ResolveStringValue", reflect.TypeOf((*MockIResolver)(nil).ResolveStringValue), ctx, reqID, flagKey, context)
+}

core/pkg/service/ofrep/models.go

@@ -73,13 +73,20 @@ func ContextErrorResponseFrom(key string) EvaluationError {
 	}
 }
 
-func BulkEvaluationContextErrorFrom() BulkEvaluationError {
+func BulkEvaluationContextError() BulkEvaluationError {
 	return BulkEvaluationError{
 		ErrorCode:    model.InvalidContextCode,
 		ErrorDetails: "Provider context is not valid",
 	}
 }
 
+func BulkEvaluationContextErrorFrom(code string, details string) BulkEvaluationError {
+	return BulkEvaluationError{
+		ErrorCode:    code,
+		ErrorDetails: details,
+	}
+}
+
 func EvaluationErrorResponseFrom(result evaluator.AnyValue) (int, EvaluationError) {
 	payload := EvaluationError{
 		Key: result.FlagKey,

core/pkg/store/flags.go

@@ -12,7 +12,7 @@ import (
 )
 
 type IStore interface {
-	GetAll(ctx context.Context) map[string]model.Flag
+	GetAll(ctx context.Context) (map[string]model.Flag, error)
 	Get(ctx context.Context, key string) (model.Flag, bool)
 	SelectorForFlag(ctx context.Context, flag model.Flag) string
 }
@@ -90,7 +90,7 @@ func (f *Flags) String() (string, error) {
 }
 
 // GetAll returns a copy of the store's state (copy in order to be concurrency safe)
-func (f *Flags) GetAll(_ context.Context) map[string]model.Flag {
+func (f *Flags) GetAll(_ context.Context) (map[string]model.Flag, error) {
 	f.mx.RLock()
 	defer f.mx.RUnlock()
 	state := make(map[string]model.Flag, len(f.Flags))
@@ -99,7 +99,7 @@ func (f *Flags) GetAll(_ context.Context) map[string]model.Flag {
 		state[key] = flag
 	}
 
-	return state
+	return state, nil
 }
 
 // Add new flags from source.
@@ -187,7 +187,12 @@ func (f *Flags) DeleteFlags(logger *logger.Logger, source string, flags map[stri
 
 	notifications := map[string]interface{}{}
 	if len(flags) == 0 {
-		allFlags := f.GetAll(ctx)
+		allFlags, err := f.GetAll(ctx)
+		if err != nil {
+			logger.Error(fmt.Sprintf("error while retrieving flags from the store: %v", err))
+			return notifications
+		}
+
 		for key, flag := range allFlags {
 			if flag.Source != source {
 				continue

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

@@ -69,7 +69,13 @@ func (s *OldFlagEvaluationService) ResolveAll(
 	if e := req.Msg.GetContext(); e != nil {
 		evalCtx = e.AsMap()
 	}
-	values := s.eval.ResolveAllValues(sCtx, reqID, evalCtx)
+
+	values, err := s.eval.ResolveAllValues(sCtx, reqID, evalCtx)
+	if err != nil {
+		s.logger.WarnWithID(reqID, fmt.Sprintf("error resolving all flags: %v", err))
+		return nil, fmt.Errorf("error resolving flags. Tracking ID: %s", reqID)
+	}
+
 	span.SetAttributes(attribute.Int("feature_flag.count", len(values)))
 	for _, value := range values {
 		// register the impression and reason for each flag evaluated

flagd/pkg/service/flag-evaluation/flag_evaluator_test.go

@@ -118,7 +118,7 @@ func TestConnectService_ResolveAll(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			eval := mock.NewMockIEvaluator(ctrl)
 			eval.EXPECT().ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).Return(
-				tt.evalRes,
+				tt.evalRes, nil,
 			).AnyTimes()
 			metrics, exp := getMetricReader()
 			s := NewOldFlagEvaluationService(

flagd/pkg/service/flag-evaluation/flag_evaluator_v2.go

@@ -68,7 +68,12 @@ func (s *FlagEvaluationService) ResolveAll(
 		evalCtx = e.AsMap()
 	}
 
-	values := s.eval.ResolveAllValues(sCtx, reqID, evalCtx)
+	values, err := s.eval.ResolveAllValues(sCtx, reqID, evalCtx)
+	if err != nil {
+		s.logger.WarnWithID(reqID, fmt.Sprintf("error resolving all flags: %v", err))
+		return nil, fmt.Errorf("error resolving flags. Tracking ID: %s", reqID)
+	}
+
 	span.SetAttributes(attribute.Int("feature_flag.count", len(values)))
 	for _, value := range values {
 		// register the impression and reason for each flag evaluated

flagd/pkg/service/flag-evaluation/flag_evaluator_v2_test.go

@@ -21,7 +21,8 @@ func TestConnectServiceV2_ResolveAll(t *testing.T) {
 	tests := map[string]struct {
 		req     *evalV1.ResolveAllRequest
 		evalRes []evaluator.AnyValue
-		wantErr error
+		evalErr error
+		wantErr bool
 		wantRes *evalV1.ResolveAllResponse
 	}{
 		"happy-path": {
@@ -52,7 +53,6 @@ func TestConnectServiceV2_ResolveAll(t *testing.T) {
 					FlagKey: "object",
 				},
 			},
-			wantErr: nil,
 			wantRes: &evalV1.ResolveAllResponse{
 				Flags: map[string]*evalV1.AnyFlag{
 					"bool": {
@@ -76,26 +76,37 @@ func TestConnectServiceV2_ResolveAll(t *testing.T) {
 				},
 			},
 		},
+		"resolver error": {
+			req:     &evalV1.ResolveAllRequest{},
+			evalRes: []evaluator.AnyValue{},
+			evalErr: errors.New("some error from internal evaluator"),
+			wantErr: true,
+		},
 	}
 	ctrl := gomock.NewController(t)
 	for name, tt := range tests {
 		t.Run(name, func(t *testing.T) {
+			// given
 			eval := mock.NewMockIEvaluator(ctrl)
 			eval.EXPECT().ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).Return(
-				tt.evalRes,
+				tt.evalRes, tt.evalErr,
 			).AnyTimes()
+
 			metrics, exp := getMetricReader()
-			s := NewFlagEvaluationService(
-				logger.NewLogger(nil, false),
-				eval,
-				&eventingConfiguration{},
-				metrics,
-			)
+			s := NewFlagEvaluationService(logger.NewLogger(nil, false), eval, &eventingConfiguration{}, metrics)
+
+			// when
 			got, err := s.ResolveAll(context.Background(), connect.NewRequest(tt.req))
-			if err != nil && !errors.Is(err, tt.wantErr) {
-				t.Errorf("ConnectService.ResolveAll() error = %v, wantErr %v", err.Error(), tt.wantErr.Error())
+
+			// then
+			if tt.wantErr {
+				if err == nil {
+					t.Error("expected error but git none")
+				}
+
 				return
 			}
+
 			var data metricdata.ResourceMetrics
 			err = exp.Collect(context.TODO(), &data)
 			require.Nil(t, err)

flagd/pkg/service/flag-evaluation/ofrep/handler.go

@@ -8,6 +8,7 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/open-feature/flagd/core/pkg/evaluator"
 	"github.com/open-feature/flagd/core/pkg/logger"
+	"github.com/open-feature/flagd/core/pkg/model"
 	"github.com/open-feature/flagd/core/pkg/service/ofrep"
 	"github.com/rs/xid"
 )
@@ -37,6 +38,7 @@ func NewOfrepHandler(logger *logger.Logger, evaluator evaluator.IEvaluator) http
 
 func (h *handler) HandleFlagEvaluation(w http.ResponseWriter, r *http.Request) {
 	requestID := xid.New().String()
+	defer h.Logger.ClearFields(requestID)
 
 	// obtain flag key
 	vars := mux.Vars(r)
@@ -66,17 +68,26 @@ func (h *handler) HandleFlagEvaluation(w http.ResponseWriter, r *http.Request) {
 
 func (h *handler) HandleBulkEvaluation(w http.ResponseWriter, r *http.Request) {
 	requestID := xid.New().String()
+	defer h.Logger.ClearFields(requestID)
 
 	request, err := extractOfrepRequest(r)
 	if err != nil {
-		h.writeJSONToResponse(http.StatusBadRequest, ofrep.BulkEvaluationContextErrorFrom(), w)
+		h.writeJSONToResponse(http.StatusBadRequest, ofrep.BulkEvaluationContextError(), w)
 		return
 	}
 
 	context := flagdContext(h.Logger, requestID, request)
-	evaluations := h.evaluator.ResolveAllValues(r.Context(), requestID, context)
+	evaluations, err := h.evaluator.ResolveAllValues(r.Context(), requestID, context)
+	if err != nil {
+		h.Logger.WarnWithID(requestID, fmt.Sprintf("error from resolver: %v", err))
+
+		res := ofrep.BulkEvaluationContextErrorFrom(model.GeneralErrorCode,
+			fmt.Sprintf("Bulk evaluation failed. Tracking ID: %s", requestID))
+		h.writeJSONToResponse(http.StatusInternalServerError, res, w)
+	} else {
 		h.writeJSONToResponse(http.StatusOK, ofrep.BulkEvaluationResponseFrom(evaluations), w)
 	}
+}
 
 func (h *handler) writeJSONToResponse(status int, payload interface{}, w http.ResponseWriter) {
 	// first marshal payload

flagd/pkg/service/flag-evaluation/ofrep/handler_test.go

@@ -155,6 +155,7 @@ func Test_handler_HandleBulkEvaluation(t *testing.T) {
 		method          string
 		input           *bytes.Reader
 		mockAnyResponse []evaluator.AnyValue
+		mockAnyError    error
 
 		expectedStatus int
 	}{
@@ -179,6 +180,14 @@ func Test_handler_HandleBulkEvaluation(t *testing.T) {
 			mockAnyResponse: []evaluator.AnyValue{genericErrorValue, flagNotFoundValue},
 			expectedStatus:  http.StatusOK,
 		},
+		{
+			name:            "handles internal errors and yield 500",
+			method:          "http.MethodPost",
+			input:           bytes.NewReader([]byte{}),
+			mockAnyResponse: []evaluator.AnyValue{},
+			mockAnyError:    errors.New("some internal error from evaluator"),
+			expectedStatus:  http.StatusInternalServerError,
+		},
 		{
 			name:            "valid context payload",
 			method:          http.MethodPost,
@@ -197,11 +206,8 @@ func Test_handler_HandleBulkEvaluation(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			eval := mock.NewMockIEvaluator(gomock.NewController(t))
-			if test.mockAnyResponse != nil {
-				eval.EXPECT().
-					ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).
-					Return(test.mockAnyResponse)
-			}
+			eval.EXPECT().ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).
+				Return(test.mockAnyResponse, test.mockAnyError).MinTimes(0)
 
 			h := handler{Logger: log, evaluator: eval}
 

flagd/pkg/service/flag-evaluation/ofrep/ofrep_service_test.go

@@ -19,7 +19,9 @@ func Test_OfrepServiceStartStop(t *testing.T) {
 	port := 18282
 	eval := mock.NewMockIEvaluator(gomock.NewController(t))
 
-	eval.EXPECT().ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).Return([]evaluator.AnyValue{})
+	eval.EXPECT().ResolveAllValues(gomock.Any(), gomock.Any(), gomock.Any()).
+		Return([]evaluator.AnyValue{}, nil)
+
 	cfg := SvcConfiguration{
 		Logger: logger.NewLogger(nil, false),
 		Port:   uint16(port),

flagd/pkg/service/flag-sync/sync-multiplexer.go

@@ -163,7 +163,11 @@ func (r *Multiplexer) SourcesAsMetadata() string {
 func (r *Multiplexer) reFill() error {
 	clear(r.selectorFlags)
 
-	all := r.store.GetAll(context.Background())
+	all, err := r.store.GetAll(context.Background())
+	if err != nil {
+		return fmt.Errorf("error retrieving flags from the store: %w", err)
+	}
+
 	bytes, err := json.Marshal(map[string]interface{}{"flags": all})
 	if err != nil {
 		return fmt.Errorf("error from marshallin: %w", err)