feat: add context-value flag (#1448)

- add the `--context-value` command line flag to pass arbitrary key
value pairs to the evaluation context

Signed-off-by: Aleksei Muratov <muratoff.alexey@gmail.com>

Makefile

@@ -68,6 +68,9 @@ uninstall:
 lint:
 	go install -v github.com/golangci/golangci-lint/cmd/golangci-lint@v1.55.2
 	$(foreach module, $(ALL_GO_MOD_DIRS), ${GOPATH}/bin/golangci-lint run --deadline=5m --timeout=5m $(module)/... || exit;)
+lint-fix:
+	go install -v github.com/golangci/golangci-lint/cmd/golangci-lint@v1.55.2
+	$(foreach module, $(ALL_GO_MOD_DIRS), ${GOPATH}/bin/golangci-lint run --fix --deadline=5m --timeout=5m $(module)/... || exit;)
 install-mockgen:
 	go install go.uber.org/mock/mockgen@v0.4.0
 mockgen: install-mockgen

core/pkg/service/iservice.go

@@ -32,6 +32,7 @@ type Configuration struct {
 	SocketPath     string
 	CORS           []string
 	Options        []connect.HandlerOption
+	ContextValues  map[string]any
 }
 
 /*

docs/reference/flag-definitions.md

@@ -184,6 +184,9 @@ For example, when accessing flagd via HTTP, the POST body may look like this:
 
 The evaluation context can be accessed in targeting rules using the `var` operation followed by the evaluation context property name.
 
+The evaluation context can be appended by arbitrary key value pairs
+via the `-X` command line flag.
+
 | Description                                                    | Example                                              |
 | -------------------------------------------------------------- | ---------------------------------------------------- |
 | Retrieve property from the evaluation context                  | `#!json { "var": "email" }`                          |

docs/reference/flagd-cli/flagd_start.md

@@ -11,6 +11,7 @@ flagd start [flags]
 ### Options
 
 ```
+  -X, --context-value stringToString    add arbitrary key value pairs to the flag evaluation context (default [])
   -C, --cors-origin strings             CORS allowed origins, * will allow all origins
   -h, --help                            help for start
   -z, --log-format string               Set the logging format, e.g. console or json (default "console")

flagd/cmd/start.go

@@ -34,11 +34,11 @@ const (
 	sourcesFlagName            = "sources"
 	syncPortFlagName           = "sync-port"
 	uriFlagName                = "uri"
+	contextValueFlagName       = "context-value"
 )
 
 func init() {
 	flags := startCmd.Flags()
-
 	// allows environment variables to use _ instead of -
 	viper.SetEnvKeyReplacer(strings.NewReplacer("-", "_")) // sync-provider-args becomes SYNC_PROVIDER_ARGS
 	viper.SetEnvPrefix("FLAGD")                            // port becomes FLAGD_PORT
@@ -78,6 +78,8 @@ func init() {
 	flags.StringP(otelCAPathFlagName, "A", "", "tls certificate authority path to use with OpenTelemetry collector")
 	flags.DurationP(otelReloadIntervalFlagName, "I", time.Hour, "how long between reloading the otel tls certificate "+
 		"from disk")
+	flags.StringToStringP(contextValueFlagName, "X", map[string]string{}, "add arbitrary key value pairs "+
+		"to the flag evaluation context")
 
 	_ = viper.BindPFlag(corsFlagName, flags.Lookup(corsFlagName))
 	_ = viper.BindPFlag(logFormatFlagName, flags.Lookup(logFormatFlagName))
@@ -95,6 +97,7 @@ func init() {
 	_ = viper.BindPFlag(uriFlagName, flags.Lookup(uriFlagName))
 	_ = viper.BindPFlag(syncPortFlagName, flags.Lookup(syncPortFlagName))
 	_ = viper.BindPFlag(ofrepPortFlagName, flags.Lookup(ofrepPortFlagName))
+	_ = viper.BindPFlag(contextValueFlagName, flags.Lookup(contextValueFlagName))
 }
 
 // startCmd represents the start command
@@ -139,6 +142,11 @@ var startCmd = &cobra.Command{
 		}
 		syncProviders = append(syncProviders, syncProvidersFromConfig...)
 
+		contextValuesToMap := make(map[string]any)
+		for k, v := range viper.GetStringMapString(contextValueFlagName) {
+			contextValuesToMap[k] = v
+		}
+
 		// Build Runtime -----------------------------------------------------------
 		rt, err := runtime.FromConfig(logger, Version, runtime.Config{
 			CORS:               viper.GetStringSlice(corsFlagName),
@@ -156,6 +164,7 @@ var startCmd = &cobra.Command{
 			ServiceSocketPath:  viper.GetString(socketPathFlagName),
 			SyncServicePort:    viper.GetUint16(syncPortFlagName),
 			SyncProviders:      syncProviders,
+			ContextValues:      contextValuesToMap,
 		})
 		if err != nil {
 			rtLogger.Fatal(err.Error())

flagd/pkg/runtime/from_config.go

@@ -40,6 +40,8 @@ type Config struct {
 
 	SyncProviders []sync.SourceConfig
 	CORS          []string
+
+	ContextValues map[string]any
 }
 
 // FromConfig builds a runtime from startup configurations
@@ -101,17 +103,20 @@ func FromConfig(logger *logger.Logger, version string, config Config) (*Runtime,
 	ofrepService, err := ofrep.NewOfrepService(jsonEvaluator, config.CORS, ofrep.SvcConfiguration{
 		Logger: logger.WithFields(zap.String("component", "OFREPService")),
 		Port:   config.OfrepServicePort,
-	})
+	},
+		config.ContextValues,
+	)
 	if err != nil {
 		return nil, fmt.Errorf("error creating ofrep service")
 	}
 
 	// flag sync service
 	flagSyncService, err := flagsync.NewSyncService(flagsync.SvcConfigurations{
-		Logger:  logger.WithFields(zap.String("component", "FlagSyncService")),
-		Port:    config.SyncServicePort,
-		Sources: sources,
-		Store:   s,
+		Logger:        logger.WithFields(zap.String("component", "FlagSyncService")),
+		Port:          config.SyncServicePort,
+		Sources:       sources,
+		Store:         s,
+		ContextValues: config.ContextValues,
 	})
 	if err != nil {
 		return nil, fmt.Errorf("error creating sync service: %w", err)
@@ -145,6 +150,7 @@ func FromConfig(logger *logger.Logger, version string, config Config) (*Runtime,
 			SocketPath:     config.ServiceSocketPath,
 			CORS:           config.CORS,
 			Options:        options,
+			ContextValues:  config.ContextValues,
 		},
 		SyncImpl: iSyncs,
 	}, nil

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

@@ -154,6 +154,7 @@ func (s *ConnectService) setupServer(svcConf service.Configuration) (net.Listene
 		s.eval,
 		s.eventingConfiguration,
 		s.metrics,
+		svcConf.ContextValues,
 	)
 
 	marshalOpts := WithJSON(
@@ -170,6 +171,7 @@ func (s *ConnectService) setupServer(svcConf service.Configuration) (net.Listene
 		s.eval,
 		s.eventingConfiguration,
 		s.metrics,
+		svcConf.ContextValues,
 	)
 
 	_, newHandler := evaluationV1.NewServiceHandler(newFes, append(svcConf.Options, marshalOpts)...)

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

@@ -32,18 +32,24 @@ type OldFlagEvaluationService struct {
 	metrics               telemetry.IMetricsRecorder
 	eventingConfiguration IEvents
 	flagEvalTracer        trace.Tracer
+	contextValues         map[string]any
 }
 
 // NewOldFlagEvaluationService creates a OldFlagEvaluationService with provided parameters
-func NewOldFlagEvaluationService(log *logger.Logger,
-	eval evaluator.IEvaluator, eventingCfg IEvents, metricsRecorder telemetry.IMetricsRecorder,
+func NewOldFlagEvaluationService(
+	log *logger.Logger,
+	eval evaluator.IEvaluator,
+	eventingCfg IEvents,
+	metricsRecorder telemetry.IMetricsRecorder,
+	contextValues map[string]any,
 ) *OldFlagEvaluationService {
 	svc := &OldFlagEvaluationService{
 		logger:                log,
 		eval:                  eval,
 		metrics:               &telemetry.NoopMetricsRecorder{},
 		eventingConfiguration: eventingCfg,
 		flagEvalTracer:        otel.Tracer("flagEvaluationService"),
+		contextValues:         contextValues,
 	}
 
 	if metricsRecorder != nil {
@@ -65,12 +71,8 @@ func (s *OldFlagEvaluationService) ResolveAll(
 	res := &schemaV1.ResolveAllResponse{
 		Flags: make(map[string]*schemaV1.AnyFlag),
 	}
-	evalCtx := map[string]any{}
-	if e := req.Msg.GetContext(); e != nil {
-		evalCtx = e.AsMap()
-	}
 
-	values, err := s.eval.ResolveAllValues(sCtx, reqID, evalCtx)
+	values, err := s.eval.ResolveAllValues(sCtx, reqID, mergeContexts(req.Msg.GetContext().AsMap(), s.contextValues))
 	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)
@@ -172,6 +174,7 @@ func (s *OldFlagEvaluationService) ResolveBoolean(
 	sCtx, span := s.flagEvalTracer.Start(ctx, "resolveBoolean", trace.WithSpanKind(trace.SpanKindServer))
 	defer span.End()
 	res := connect.NewResponse(&schemaV1.ResolveBooleanResponse{})
+
 	err := resolve[bool](
 		sCtx,
 		s.logger,
@@ -180,6 +183,7 @@ func (s *OldFlagEvaluationService) ResolveBoolean(
 		req.Msg.GetContext(),
 		&booleanResponse{schemaV1Resp: res},
 		s.metrics,
+		s.contextValues,
 	)
 	if err != nil {
 		span.RecordError(err)
@@ -206,6 +210,7 @@ func (s *OldFlagEvaluationService) ResolveString(
 		req.Msg.GetContext(),
 		&stringResponse{schemaV1Resp: res},
 		s.metrics,
+		s.contextValues,
 	)
 	if err != nil {
 		span.RecordError(err)
@@ -232,6 +237,7 @@ func (s *OldFlagEvaluationService) ResolveInt(
 		req.Msg.GetContext(),
 		&intResponse{schemaV1Resp: res},
 		s.metrics,
+		s.contextValues,
 	)
 	if err != nil {
 		span.RecordError(err)
@@ -258,6 +264,7 @@ func (s *OldFlagEvaluationService) ResolveFloat(
 		req.Msg.GetContext(),
 		&floatResponse{schemaV1Resp: res},
 		s.metrics,
+		s.contextValues,
 	)
 	if err != nil {
 		span.RecordError(err)
@@ -284,6 +291,7 @@ func (s *OldFlagEvaluationService) ResolveObject(
 		req.Msg.GetContext(),
 		&objectResponse{schemaV1Resp: res},
 		s.metrics,
+		s.contextValues,
 	)
 	if err != nil {
 		span.RecordError(err)
@@ -293,21 +301,36 @@ func (s *OldFlagEvaluationService) ResolveObject(
 	return res, err
 }
 
+// mergeContexts combines values from the request context with the values from the config --context-values flag.
+// Request context values have a higher priority.
+func mergeContexts(reqCtx, configFlagsCtx map[string]any) map[string]any {
+	merged := make(map[string]any)
+	for k, v := range reqCtx {
+		merged[k] = v
+	}
+	for k, v := range configFlagsCtx {
+		merged[k] = v
+	}
+	return merged
+}
+
 // resolve is a generic flag resolver
 func resolve[T constraints](ctx context.Context, logger *logger.Logger, resolver resolverSignature[T], flagKey string,
 	evaluationContext *structpb.Struct, resp response[T], metrics telemetry.IMetricsRecorder,
+	configContextValues map[string]any,
 ) error {
 	reqID := xid.New().String()
 	defer logger.ClearFields(reqID)
 
+	mergedContext := mergeContexts(evaluationContext.AsMap(), configContextValues)
 	logger.WriteFields(
 		reqID,
 		zap.String("flag-key", flagKey),
-		zap.Strings("context-keys", formatContextKeys(evaluationContext)),
+		zap.Strings("context-keys", formatContextKeys(mergedContext)),
 	)
 
 	var evalErrFormatted error
-	result, variant, reason, metadata, evalErr := resolver(ctx, reqID, flagKey, evaluationContext.AsMap())
+	result, variant, reason, metadata, evalErr := resolver(ctx, reqID, flagKey, mergedContext)
 	if evalErr != nil {
 		logger.WarnWithID(reqID, fmt.Sprintf("returning error response, reason: %v", evalErr))
 		reason = model.ErrorReason
@@ -329,9 +352,9 @@ func resolve[T constraints](ctx context.Context, logger *logger.Logger, resolver
 	return evalErrFormatted
 }
 
-func formatContextKeys(context *structpb.Struct) []string {
+func formatContextKeys(context map[string]any) []string {
 	res := []string{}
-	for k := range context.AsMap() {
+	for k := range context {
 		res = append(res, k)
 	}
 	return res

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

@@ -128,6 +128,7 @@ func TestConnectService_ResolveAll(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 			got, err := s.ResolveAll(context.Background(), connect.NewRequest(tt.req))
 			if err != nil && !errors.Is(err, tt.wantErr) {
@@ -235,6 +236,7 @@ func TestFlag_Evaluation_ResolveBoolean(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 			got, err := s.ResolveBoolean(tt.functionArgs.ctx, connect.NewRequest(tt.functionArgs.req))
 			if (err != nil) && !errors.Is(err, tt.wantErr) {
@@ -290,6 +292,7 @@ func BenchmarkFlag_Evaluation_ResolveBoolean(b *testing.B) {
 			eval,
 			&eventingConfiguration{},
 			metrics,
+			nil,
 		)
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
@@ -388,6 +391,7 @@ func TestFlag_Evaluation_ResolveString(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 			got, err := s.ResolveString(tt.functionArgs.ctx, connect.NewRequest(tt.functionArgs.req))
 			if (err != nil) && !errors.Is(err, tt.wantErr) {
@@ -443,6 +447,7 @@ func BenchmarkFlag_Evaluation_ResolveString(b *testing.B) {
 			eval,
 			&eventingConfiguration{},
 			metrics,
+			nil,
 		)
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
@@ -540,6 +545,7 @@ func TestFlag_Evaluation_ResolveFloat(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 			got, err := s.ResolveFloat(tt.functionArgs.ctx, connect.NewRequest(tt.functionArgs.req))
 			if (err != nil) && !errors.Is(err, tt.wantErr) {
@@ -595,6 +601,7 @@ func BenchmarkFlag_Evaluation_ResolveFloat(b *testing.B) {
 			eval,
 			&eventingConfiguration{},
 			metrics,
+			nil,
 		)
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
@@ -692,6 +699,7 @@ func TestFlag_Evaluation_ResolveInt(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 			got, err := s.ResolveInt(tt.functionArgs.ctx, connect.NewRequest(tt.functionArgs.req))
 			if (err != nil) && !errors.Is(err, tt.wantErr) {
@@ -747,6 +755,7 @@ func BenchmarkFlag_Evaluation_ResolveInt(b *testing.B) {
 			eval,
 			&eventingConfiguration{},
 			metrics,
+			nil,
 		)
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
@@ -847,6 +856,7 @@ func TestFlag_Evaluation_ResolveObject(t *testing.T) {
 				eval,
 				&eventingConfiguration{},
 				metrics,
+				nil,
 			)
 
 			outParsed, err := structpb.NewStruct(tt.evalFields.result)
@@ -910,6 +920,7 @@ func BenchmarkFlag_Evaluation_ResolveObject(b *testing.B) {
 			eval,
 			&eventingConfiguration{},
 			metrics,
+			nil,
 		)
 		if name != "eval returns error" {
 			outParsed, err := structpb.NewStruct(tt.evalFields.result)