chore: Fail initialization if data system doesn't archive target avai…

…lability (#232)

internal/datasystem/data_availability.go

@@ -11,3 +11,13 @@ const (
 	// Refreshed means the SDK has obtained, at least once, the latest known data from LaunchDarkly.
 	Refreshed = DataAvailability("refreshed")
 )
+
+// AtLeast returns true if the DataAvailability is at least as good as the
+// other DataAvailability in terms of data quality.
+func (da DataAvailability) AtLeast(other DataAvailability) bool {
+	if da == other {
+		return true
+	}
+
+	return da == Refreshed || (da == Cached && other == Defaults)
+}

internal/datasystem/data_availability_test.go

@@ -0,0 +1,21 @@
+package datasystem
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDataAvailibilityAtLeast(t *testing.T) {
+	assert.True(t, Refreshed.AtLeast(Refreshed))
+	assert.True(t, Refreshed.AtLeast(Cached))
+	assert.True(t, Refreshed.AtLeast(Defaults))
+
+	assert.False(t, Cached.AtLeast(Refreshed))
+	assert.True(t, Cached.AtLeast(Cached))
+	assert.True(t, Cached.AtLeast(Defaults))
+
+	assert.False(t, Defaults.AtLeast(Refreshed))
+	assert.False(t, Defaults.AtLeast(Cached))
+	assert.True(t, Defaults.AtLeast(Defaults))
+}

internal/datasystem/fdv1_datasystem.go

@@ -155,6 +155,11 @@ func (f *FDv1) DataAvailability() DataAvailability {
 	return Defaults
 }
 
+//nolint:revive // Data system implementation.
+func (f *FDv1) TargetAvailability() DataAvailability {
+	return Refreshed
+}
+
 //nolint:revive // Data system implementation.
 func (f *FDv1) Store() subsystems.ReadOnlyStore {
 	return f.dataStore

internal/datasystem/fdv2_datasystem.go

@@ -262,12 +262,23 @@ func (f *FDv2) DataAvailability() DataAvailability {
 	if f.store.Selector().IsDefined() {
 		return Refreshed
 	}
-	if f.store.IsInitialized() {
+
+	if !f.hasDataSources() || f.store.IsInitialized() {
 		return Cached
 	}
+
 	return Defaults
 }
 
+//nolint:revive // DataSystem method.
+func (f *FDv2) TargetAvailability() DataAvailability {
+	if f.hasDataSources() {
+		return Refreshed
+	}
+
+	return Cached
+}
+
 //nolint:revive // DataSystem method.
 func (f *FDv2) DataSourceStatusBroadcaster() *internal.Broadcaster[interfaces.DataSourceStatus] {
 	return f.broadcasters.dataSourceStatus

ldclient.go

@@ -88,6 +88,9 @@ type dataSystem interface {
 
 	// DataAvailability indicates what form of data is available.
 	DataAvailability() datasystem.DataAvailability
+
+	/// TargetAvailability indicates the ideal form of data available.
+	TargetAvailability() datasystem.DataAvailability
 }
 
 var (
@@ -342,13 +345,14 @@ func MakeCustomClient(sdkKey string, config Config, waitFor time.Duration) (*LDC
 		for {
 			select {
 			case <-closeWhenReady:
-				if client.dataSystem.DataAvailability() != datasystem.Refreshed {
-					loggers.Warn("LaunchDarkly client initialization failed")
-					return client, ErrInitializationFailed
+				if client.dataSystem.DataAvailability().AtLeast(client.dataSystem.TargetAvailability()) {
+					loggers.Info("Initialized LaunchDarkly client")
+					return client, nil
 				}
 
-				loggers.Info("Initialized LaunchDarkly client")
-				return client, nil
+				loggers.Warn("LaunchDarkly client initialization failed")
+				return client, ErrInitializationFailed
+
 			case <-timeout:
 				loggers.Warn("Timeout encountered waiting for LaunchDarkly client initialization")
 				go func() { <-closeWhenReady }() // Don't block the DataSource when not waiting

ldcomponents/data_system_configuration_builder.go

@@ -170,6 +170,7 @@ func (d *DataSystemConfigurationBuilder) Build(
 		}
 		conf.Store = store
 	}
+	conf.StoreMode = d.storeMode
 	for i, initializerBuilder := range d.initializerBuilders {
 		if initializerBuilder == nil {
 			return ss.DataSystemConfiguration{},