fix: client init state should not regress when data source interrupted

libs/client-sdk/src/client_impl.cpp

@@ -134,19 +134,28 @@
     run_thread_ = std::move(std::thread([&]() { ioc_.run(); }));
 }
 
-// Was an attempt made to initialize the data source, and did that attempt
-// succeed? The data source being connected, or not being connected due to
-// offline mode, both represent successful terminal states.
+// Returns true if the SDK can be considered initialized. We have defined
+// explicit configuration of offline mode as initialized.
+//
+// When online, we're initialized if we've obtained a payload and are healthy
+// (kValid) or obtained a payload and are unhealthy (kInterrupted).
+//
+// The purpose of this concept is to enable:
+//
+// (1) Resolving the StartAsync() promise. Once the SDK is no longer
+// initializing, this promise needs to indicate if the process was successful
+// or not.
+//
+// (2) Providing a getter for (1), if the user didn't check the promise or
+// otherwise need to poll the state. That's the Initialized() method.
+//
+// (3) As a diagnostic during evaluation, to log a message warning that a
+// cached (if persistence is being used) or default (if not) value will be
+// returned because the SDK is not yet initialized.
 static bool IsInitializedSuccessfully(DataSourceStatus::DataSourceState state) {
     return (state == DataSourceStatus::DataSourceState::kValid ||
-            state == DataSourceStatus::DataSourceState::kSetOffline);
-}
-
-// Was any attempt made to initialize the data source (with a successful or
-// permanent failure outcome?)
-static bool IsInitialized(DataSourceStatus::DataSourceState state) {
-    return IsInitializedSuccessfully(state) ||
-           (state == DataSourceStatus::DataSourceState::kShutdown);
+            state == DataSourceStatus::DataSourceState::kSetOffline ||
+            state == DataSourceStatus::DataSourceState::kInterrupted);
 }
 
 std::future<bool> ClientImpl::IdentifyAsync(Context context) {
@@ -155,7 +164,7 @@
     event_processor_->SendAsync(events::IdentifyEventParams{
         std::chrono::system_clock::now(), std::move(context)});
 
-    return StartAsyncInternal(IsInitializedSuccessfully);
+    return StartAsyncInternal();
 }
 
 void ClientImpl::RestartDataSource() {
@@ -169,16 +178,16 @@
     data_source_->ShutdownAsync(start_op);
 }
 
-std::future<bool> ClientImpl::StartAsyncInternal(
-    std::function<bool(DataSourceStatus::DataSourceState)> result_predicate) {
+std::future<bool> ClientImpl::StartAsyncInternal() {
     auto init_promise = std::make_shared<std::promise<bool>>();
     auto init_future = init_promise->get_future();
 
     status_manager_.OnDataSourceStatusChangeEx(
-        [result = std::move(result_predicate),
-         init_promise](data_sources::DataSourceStatus const& status) {
-            if (auto const state = status.State(); IsInitialized(state)) {
-                init_promise->set_value(result(status.State()));
+        [init_promise](data_sources::DataSourceStatus const& status) {
+            if (auto const state = status.State();
+                state != DataSourceStatus::DataSourceState::kInitializing) {
+                init_promise->set_value(
+                    IsInitializedSuccessfully(status.State()));
                 return true; /* delete this change listener since the desired
                                 state was reached */
             }
@@ -191,7 +200,7 @@
 }
 
 std::future<bool> ClientImpl::StartAsync() {
-    return StartAsyncInternal(IsInitializedSuccessfully);
+    return StartAsyncInternal();
 }
 
 bool ClientImpl::Initialized() const {
@@ -202,7 +211,7 @@
     std::unordered_map<Client::FlagKey, Value> result;
     for (auto& [key, descriptor] : flag_manager_.Store().GetAll()) {
         if (descriptor->item) {
             result.try_emplace(key, descriptor->item->Detail().Value());
         }
     }
     return result;
@@ -237,7 +246,7 @@
 }
 
 template <typename T>
 EvaluationDetail<T> ClientImpl::VariationInternal(FlagKey const& key,
                                                   Value default_value,
                                                   bool check_type,
                                                   bool detailed) {
@@ -293,7 +302,7 @@
 
     LD_ASSERT(desc->item);
 
     auto const& flag = *(desc->item);
     auto const& detail = flag.Detail();
 
     if (check_type && default_value.Type() != Value::Type::kNull &&

libs/client-sdk/src/client_impl.hpp

@@ -28,7 +28,7 @@
 namespace launchdarkly::client_side {
 class ClientImpl : public IClient {
    public:
     ClientImpl(Config config, Context context, std::string const& version);
 
     ClientImpl(ClientImpl&&) = delete;
     ClientImpl(ClientImpl const&) = delete;
@@ -84,7 +84,7 @@
 
     flag_manager::IFlagNotifier& FlagNotifier() override;
 
     ~ClientImpl();
 
     std::future<bool> StartAsync() override;
 
@@ -99,7 +99,7 @@
                        std::optional<double> metric_value);
 
     template <typename F>
     auto ReadContextSynchronized(F fn) const
         -> std::invoke_result_t<F, Context const&> {
         std::shared_lock lock(context_mutex_);
         return fn(context_);
@@ -109,10 +109,7 @@
 
     void RestartDataSource();
 
-    std::future<bool> StartAsyncInternal(
-        std::function<bool(data_sources::DataSourceStatus::DataSourceState)>
-            predicate);
-
+    std::future<bool> StartAsyncInternal();
     Config config_;
     Logger logger_;
 

libs/client-sdk/tests/client_c_bindings_test.cpp

@@ -14,7 +14,7 @@
 TEST(ClientBindings, MinimalInstantiation) {
     LDClientConfigBuilder cfg_builder = LDClientConfigBuilder_New("sdk-123");
 
     LDClientConfig config;
     LDStatus status = LDClientConfigBuilder_Build(cfg_builder, &config);
     ASSERT_TRUE(LDStatus_Ok(status));
 
@@ -33,7 +33,7 @@
 }
 
 void FlagListenerFunction(char const* flag_key,
                           LDValue new_value,
                           LDValue old_value,
                           bool deleted,
                           void* user_data) {}
@@ -148,6 +148,8 @@
     bool success = false;
     LDClientSDK_Start(sdk, 3000, &success);
 
+    EXPECT_TRUE(success);
+
     LDDataSourceStatus status_2 = LDClientSDK_DataSourceStatus_Status(sdk);
     EXPECT_EQ(LD_DATASOURCESTATUS_STATE_OFFLINE,
               LDDataSourceStatus_GetState(status_2));
@@ -156,6 +158,8 @@
 
     EXPECT_NE(0, LDDataSourceStatus_StateSince(status_2));
 
+    EXPECT_TRUE(LDClientSDK_Initialized(sdk));
+
     LDDataSourceStatus_Free(status_1);
     LDDataSourceStatus_Free(status_2);
     LDClientSDK_Free(sdk);