Support of evaluation context enrichment (#1285)

cmd/relayproxy/config/config.go

@@ -171,9 +171,18 @@ type Config struct {
 	// APIKeys list of API keys that authorized to use endpoints
 	APIKeys []string `mapstructure:"apiKeys" koanf:"apikeys"`
 
-	// StartAsAwsLambda (optional) if true the relay proxy will start ready to be launch as AWS Lambda
+	// StartAsAwsLambda (optional) if true, the relay proxy will start ready to be launched as AWS Lambda
 	StartAsAwsLambda bool `mapstructure:"startAsAwsLambda" koanf:"startasawslambda"`
 
+	// EvaluationContextEnrichment (optional) will be merged with the evaluation context sent during the evaluation.
+	// It is useful to add common attributes to all the evaluations, such as a server version, environment, ...
+	//
+	// All those fields will be included in the custom attributes of the evaluation context,
+	// if in the evaluation context you have a field with the same name,
+	// it will be overridden by the evaluationContextEnrichment.
+	// Default: nil
+	EvaluationContextEnrichment map[string]interface{} `mapstructure:"evaluationContextEnrichment" koanf:"evaluationcontextenrichment"` //nolint: lll
+
 	// ---- private fields
 
 	// apiKeySet is the internal representation of the list of api keys configured

cmd/relayproxy/service/gofeatureflag.go

@@ -75,16 +75,17 @@ func NewGoFeatureFlagClient(
 	notif = append(notif, notifiers...)
 
 	f := ffclient.Config{
-		PollingInterval:         time.Duration(proxyConf.PollingInterval) * time.Millisecond,
-		Logger:                  zap.NewStdLog(logger),
-		Context:                 context.Background(),
-		Retriever:               mainRetriever,
-		Retrievers:              retrievers,
-		Notifiers:               notif,
-		FileFormat:              proxyConf.FileFormat,
-		DataExporter:            exp,
-		StartWithRetrieverError: proxyConf.StartWithRetrieverError,
-		EnablePollingJitter:     proxyConf.EnablePollingJitter,
+		PollingInterval:             time.Duration(proxyConf.PollingInterval) * time.Millisecond,
+		Logger:                      zap.NewStdLog(logger),
+		Context:                     context.Background(),
+		Retriever:                   mainRetriever,
+		Retrievers:                  retrievers,
+		Notifiers:                   notif,
+		FileFormat:                  proxyConf.FileFormat,
+		DataExporter:                exp,
+		StartWithRetrieverError:     proxyConf.StartWithRetrieverError,
+		EnablePollingJitter:         proxyConf.EnablePollingJitter,
+		EvaluationContextEnrichment: proxyConf.EvaluationContextEnrichment,
 	}
 
 	return ffclient.New(f)

config.go

@@ -69,6 +69,14 @@ type Config struct {
 	// No notification will be sent neither.
 	// Default: false
 	Offline bool
+
+	// EvaluationContextEnrichment (optional) will be merged with the evaluation context sent during the evaluation.
+	// It is useful to add common attributes to all the evaluation, such as a server version, environment, ...
+	//
+	// All those fields will be included in the custom attributes of the evaluation context,
+	// if in the evaluation context you have a field with the same name, it will override the common one.
+	// Default: nil
+	EvaluationContextEnrichment map[string]interface{}
 }
 
 // GetRetrievers returns a retriever.Retriever configure with the retriever available in the config.
@@ -78,7 +86,7 @@ func (c *Config) GetRetrievers() ([]retriever.Retriever, error) {
 	}
 
 	retrievers := make([]retriever.Retriever, 0)
-	// If we have both Retriever and Retrievers fields configured we are 1st looking at what is available
+	// If we have both Retriever and Retrievers fields configured, we are 1st looking at what is available
 	// in Retriever before looking at what is in Retrievers.
 	if c.Retriever != nil {
 		retrievers = append(retrievers, c.Retriever)

examples/retriever_file/main.go

@@ -42,6 +42,7 @@ func main() {
 	user1 := ffcontext.
 		NewEvaluationContextBuilder("aea2fdc1-b9a0-417a-b707-0c9083de68e3").
 		AddCustom("anonymous", true).
+		AddCustom("environment", "dev").
 		Build()
 	user2 := ffcontext.NewEvaluationContext("332460b9-a8aa-4f7a-bc5d-9cc33632df9a")
 	user3 := ffcontext.NewEvaluationContextBuilder("785a14bf-d2c5-4caa-9c70-2bbc4e3732a5").

internal/flag/context.go

@@ -1,11 +1,21 @@
 package flag
 
 type Context struct {
-	// Environment is the name of your current env
-	// this value will be added to the custom information of your user and,
-	// it will allow to create rules based on this environment,
-	Environment string
+	// EvaluationContextEnrichment will be merged with the evaluation context sent during the evaluation.
+	// It is useful to add common attributes to all the evaluation, such as a server version, environment, ...
+	//
+	// All those fields will be included in the custom attributes of the evaluation context,
+	// if in the evaluation context you have a field with the same name, it will override the common one.
+	// Default: nil
+	EvaluationContextEnrichment map[string]interface{}
 
 	// DefaultSdkValue is the default value of the SDK when calling the variation.
 	DefaultSdkValue interface{}
 }
+
+func (s *Context) AddIntoEvaluationContextEnrichment(key string, value interface{}) {
+	if s.EvaluationContextEnrichment == nil {
+		s.EvaluationContextEnrichment = make(map[string]interface{})
+	}
+	s.EvaluationContextEnrichment[key] = value
+}

internal/flag/context_test.go

@@ -0,0 +1,57 @@
+package flag_test
+
+import (
+	"github.com/stretchr/testify/assert"
+	"github.com/thomaspoignant/go-feature-flag/internal/flag"
+	"testing"
+)
+
+func TestContext_AddIntoEvaluationContextEnrichment(t *testing.T) {
+	type args struct {
+		key   string
+		value interface{}
+	}
+	tests := []struct {
+		name                        string
+		EvaluationContextEnrichment map[string]interface{}
+		args                        args
+		expected                    interface{}
+	}{
+		{
+			name:                        "Add a new key to a nil map",
+			EvaluationContextEnrichment: nil,
+			args: args{
+				key:   "env",
+				value: "prod",
+			},
+			expected: "prod",
+		},
+		{
+			name:                        "Add a new key to an existing map",
+			EvaluationContextEnrichment: map[string]interface{}{"john": "doe"},
+			args: args{
+				key:   "env",
+				value: "prod",
+			},
+			expected: "prod",
+		},
+		{
+			name:                        "Override an existing key",
+			EvaluationContextEnrichment: map[string]interface{}{"env": "dev"},
+			args: args{
+				key:   "env",
+				value: "prod",
+			},
+			expected: "prod",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &flag.Context{
+				EvaluationContextEnrichment: tt.EvaluationContextEnrichment,
+			}
+			s.AddIntoEvaluationContextEnrichment(tt.args.key, tt.args.value)
+			assert.Equal(t, tt.expected, s.EvaluationContextEnrichment[tt.args.key])
+		})
+	}
+}

internal/flag/internal_flag.go

@@ -3,6 +3,7 @@ package flag
 import (
 	"fmt"
 	"github.com/thomaspoignant/go-feature-flag/ffcontext"
+	"maps"
 	"time"
 
 	"github.com/thomaspoignant/go-feature-flag/internal/internalerror"
@@ -63,8 +64,8 @@ func (f *InternalFlag) Value(
 ) (interface{}, ResolutionDetails) {
 	f.applyScheduledRolloutSteps()
 
-	if flagContext.Environment != "" {
-		evaluationCtx.AddCustomAttribute("env", flagContext.Environment)
+	if flagContext.EvaluationContextEnrichment != nil {
+		maps.Copy(evaluationCtx.GetCustom(), flagContext.EvaluationContextEnrichment)
 	}
 
 	if f.IsDisable() || f.isExperimentationOver() {