feat: Add the ability to persist and restore flag configuration.

CMakeLists.txt

@@ -26,6 +26,7 @@ option(BUILD_TESTING "Enable C++ unit tests." ON)
 option(TESTING_SANITIZERS "Enable sanitizers for unit tests." ON)
 
 if (BUILD_TESTING)
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -D_GLIBCXX_DEBUG")
     add_compile_definitions(LAUNCHDARKLY_USE_ASSERT)
     if (TESTING_SANITIZERS)
         if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")

apps/hello-cpp/main.cpp

@@ -4,6 +4,8 @@
 
 #include <launchdarkly/context_builder.hpp>
 
+#include <filesystem>
+#include <fstream>
 #include <iostream>
 
 namespace net = boost::asio;  // from <boost/asio.hpp>
@@ -13,8 +15,56 @@ using launchdarkly::LogLevel;
 using launchdarkly::client_side::Client;
 using launchdarkly::client_side::ConfigBuilder;
 using launchdarkly::client_side::DataSourceBuilder;
+using launchdarkly::client_side::PersistenceBuilder;
 using launchdarkly::config::shared::builders::LoggingBuilder;
 
+class FilePersistence : public IPersistence {
+   public:
+    FilePersistence(std::string directory) : directory_(std::move(directory)) {
+        std::filesystem::create_directories(directory_);
+    }
+    void Set(std::string storage_namespace,
+                  std::string key,
+                  std::string data) noexcept override {
+        try {
+            std::ofstream file;
+            file.open(MakePath(storage_namespace, key));
+            file << data;
+            file.close();
+        } catch (...) {
+            std::cout << "Problem writing" << std::endl;
+        }
+    }
+
+    void Remove(std::string storage_namespace,
+                     std::string key) noexcept override {
+        std::filesystem::remove(MakePath(storage_namespace, key));
+    }
+
+    std::optional<std::string> Read(std::string storage_namespace,
+                                    std::string key) noexcept override {
+        auto path = MakePath(storage_namespace, key);
+
+        try {
+            if (std::filesystem::exists(path)) {
+                std::ifstream file(path);
+                std::stringstream buffer;
+                buffer << file.rdbuf();
+                return buffer.str();
+            }
+        } catch (...) {
+            std::cout << "Problem reading" << std::endl;
+        }
+        return std::nullopt;
+    }
+
+   private:
+    std::string MakePath(std::string storage_namespace, std::string key) {
+        return directory_ + "/" + storage_namespace + "_" + key;
+    }
+    std::string directory_;
+};
+
 int main() {
     net::io_context ioc;
 
@@ -39,6 +89,8 @@ int main() {
     config_builder.Logging().Logging(
         LoggingBuilder::BasicLogging().Level(LogLevel::kDebug));
     config_builder.Events().FlushInterval(std::chrono::seconds(5));
+    config_builder.Persistence().Custom(
+        std::make_shared<FilePersistence>("ld_persist"));
 
     auto config = config_builder.Build();
     if (!config) {
@@ -49,6 +101,11 @@ int main() {
     Client client(std::move(*config),
                   ContextBuilder().kind("user", "ryan").build());
 
+    auto before_init = client.BoolVariationDetail("my-boolean-flag", false);
+    // This should be the cached version from our persistence, if the
+    // persistence is populated.
+    std::cout << "Before Init Complete: " << *before_init << std::endl;
+
     std::cout << "Initial Status: " << client.DataSourceStatus().Status()
               << std::endl;
 
@@ -68,6 +125,27 @@ int main() {
         std::cout << "Reason was: " << *reason << std::endl;
     }
 
+    // Identify a series of contexts.
+    for (auto context_index = 0; context_index < 4; context_index++) {
+        std::cout << "Identifying user: "
+                  << "ryan" << context_index << std::endl;
+        auto future = client.IdentifyAsync(
+            ContextBuilder()
+                .kind("user", "ryan" + std::to_string(context_index))
+                .build());
+        auto before_ident =
+            client.BoolVariationDetail("my-boolean-flag", false);
+        future.get();
+        auto after_ident = client.BoolVariationDetail("my-boolean-flag", false);
+
+        std::cout << "For: "
+                  << "ryan" << context_index << ": "
+                  << "Before ident complete: " << *before_init
+                  << " After: " << *after_ident << std::endl;
+
+        sleep(1);
+    }
+
     // Sit around.
     std::cout << "Press enter to exit" << std::endl << std::endl;
     std::cin.get();

libs/client-sdk/src/CMakeLists.txt

@@ -8,11 +8,10 @@ file(GLOB HEADER_LIST CONFIGURE_DEPENDS
 add_library(${LIBNAME}
         ${HEADER_LIST}
         data_sources/streaming_data_source.cpp
-        data_sources/base_64.cpp
         data_sources/data_source_event_handler.cpp
         data_sources/data_source_update_sink.cpp
         data_sources/polling_data_source.cpp
-        flag_manager/flag_manager.cpp
+        flag_manager/flag_store.cpp
         flag_manager/flag_updater.cpp
         flag_manager/flag_change_event.cpp
         data_sources/data_source_status.cpp
@@ -22,7 +21,6 @@ add_library(${LIBNAME}
         boost_signal_connection.cpp
         client_impl.cpp
         client.cpp
-        data_sources/base_64.hpp
         boost_signal_connection.hpp
         client_impl.hpp
         data_sources/data_source.hpp
@@ -33,9 +31,14 @@ add_library(${LIBNAME}
         data_sources/streaming_data_source.hpp
         event_processor/event_processor.hpp
         event_processor/null_event_processor.hpp
-        flag_manager/flag_manager.hpp
+        flag_manager/flag_store.hpp
         flag_manager/flag_updater.hpp
         event_processor.hpp
+        flag_manager/context_index.cpp
+        serialization/json_all_flags.hpp
+        serialization/json_all_flags.cpp
+        flag_manager/flag_manager.cpp
+        flag_manager/flag_persistence.cpp
         bindings/c/sdk.cpp)
 
 target_link_libraries(${LIBNAME}

libs/client-sdk/src/client_impl.cpp

@@ -1,15 +1,17 @@
 
 #include <chrono>
+
 #include <optional>
 #include <utility>
 
 #include "client_impl.hpp"
 #include "data_sources/polling_data_source.hpp"
 #include "data_sources/streaming_data_source.hpp"
+
 #include "event_processor/event_processor.hpp"
 #include "event_processor/null_event_processor.hpp"
 
-#include <launchdarkly/config/shared/built/logging.hpp>
+#include <launchdarkly/encoding/sha_256.hpp>
 #include <launchdarkly/logging/console_backend.hpp>
 #include <launchdarkly/logging/null_logger.hpp>
 
@@ -29,18 +31,18 @@ static std::shared_ptr<IDataSource> MakeDataSource(
     Config const& config,
     Context const& context,
     boost::asio::any_io_executor const& executor,
-    flag_manager::FlagUpdater& flag_updater,
+    IDataSourceUpdateSink& flag_updater,
     data_sources::DataSourceStatusManager& status_manager,
     Logger& logger) {
     if (config.DataSourceConfig().method.index() == 0) {
         // TODO: use initial reconnect delay.
         return std::make_shared<
             launchdarkly::client_side::data_sources::StreamingDataSource>(
-            config, executor, context, &flag_updater, status_manager, logger);
+            config, executor, context, flag_updater, status_manager, logger);
     }
     return std::make_shared<
         launchdarkly::client_side::data_sources::PollingDataSource>(
-        config, executor, context, &flag_updater, status_manager, logger);
+        config, executor, context, flag_updater, status_manager, logger);
 }
 
 static Logger MakeLogger(config::shared::built::Logging const& config) {
@@ -54,20 +56,34 @@ static Logger MakeLogger(config::shared::built::Logging const& config) {
         std::make_shared<logging::ConsoleBackend>(config.level, config.tag)};
 }
 
+static std::shared_ptr<IPersistence> MakePersistence(Config const& config) {
+    auto persistence = config.Persistence();
+    if (persistence.disable_persistence) {
+        return nullptr;
+    }
+    return persistence.implementation;
+}
+
 ClientImpl::ClientImpl(Config config, Context context)
     : config_(config),
       logger_(MakeLogger(config.Logging())),
       ioc_(kAsioConcurrencyHint),
       context_(std::move(context)),
+      flag_manager_(config.SdkKey(),
+                    logger_,
+                    config.Persistence().max_contexts_,
+                    MakePersistence(config)),
       data_source_factory_([this]() {
           return MakeDataSource(config_, context_, ioc_.get_executor(),
-                                flag_updater_, status_manager_, logger_);
+                                flag_manager_.Updater(), status_manager_,
+                                logger_);
       }),
       data_source_(data_source_factory_()),
       event_processor_(nullptr),
-      flag_updater_(flag_manager_),
       initialized_(false),
       eval_reasons_available_(config.DataSourceConfig().with_reasons) {
+    flag_manager_.LoadCache(context_);
+
     if (config.Events().Enabled()) {
         event_processor_ = std::make_unique<EventProcessor>(ioc_.get_executor(),
                                                             config, logger_);
@@ -103,7 +119,7 @@ bool ClientImpl::Initialized() const {
 
 std::unordered_map<Client::FlagKey, Value> ClientImpl::AllFlags() const {
     std::unordered_map<Client::FlagKey, Value> result;
-    for (auto& [key, descriptor] : flag_manager_.GetAll()) {
+    for (auto& [key, descriptor] : flag_manager_.Store().GetAll()) {
         if (descriptor->flag) {
             result.try_emplace(key, descriptor->flag->detail().value());
         }
@@ -140,6 +156,7 @@ void ClientImpl::FlushAsync() {
 }
 
 std::future<void> ClientImpl::IdentifyAsync(Context context) {
+    flag_manager_.LoadCache(context);
     auto identify_promise = std::make_shared<std::promise<void>>();
     auto fut = identify_promise->get_future();
     data_source_->ShutdownAsync(
@@ -161,7 +178,7 @@ EvaluationDetail<T> ClientImpl::VariationInternal(FlagKey const& key,
                                                   Value default_value,
                                                   bool check_type,
                                                   bool detailed) {
-    auto desc = flag_manager_.Get(key);
+    auto desc = flag_manager_.Store().Get(key);
 
     events::client::FeatureEventParams event = {
         std::chrono::system_clock::now(),
@@ -206,7 +223,7 @@ EvaluationDetail<T> ClientImpl::VariationInternal(FlagKey const& key,
                                    std::move(error_reason));
 
     } else if (!Initialized()) {
-        LD_LOG(logger_, LogLevel::kWarn)
+        LD_LOG(logger_, LogLevel::kInfo)
             << "LaunchDarkly client has not yet been initialized. "
                "Returning cached value";
     }
@@ -308,7 +325,7 @@ data_sources::IDataSourceStatusProvider& ClientImpl::DataSourceStatus() {
 }
 
 flag_manager::IFlagNotifier& ClientImpl::FlagNotifier() {
-    return flag_updater_;
+    return flag_manager_.Notifier();
 }
 
 void ClientImpl::WaitForReadySync(std::chrono::milliseconds timeout) {

libs/client-sdk/src/client_impl.hpp

@@ -25,7 +25,6 @@
 #include "data_sources/data_source_status_manager.hpp"
 #include "event_processor.hpp"
 #include "flag_manager/flag_manager.hpp"
-#include "flag_manager/flag_updater.hpp"
 
 namespace launchdarkly::client_side {
 class ClientImpl : public IClient {
@@ -109,17 +108,15 @@ class ClientImpl : public IClient {
 
     void UpdateContextSynchronized(Context context);
 
-    void OnDataSourceShutdown(Context context,
-                              std::function<void()> user_completion);
-
+    Logger logger_;
     Config config_;
 
-    Logger logger_;
     boost::asio::io_context ioc_;
 
     Context context_;
     mutable std::shared_mutex context_mutex_;
 
+    flag_manager::FlagManager flag_manager_;
     std::function<std::shared_ptr<IDataSource>()> data_source_factory_;
 
     std::shared_ptr<IDataSource> data_source_;
@@ -131,8 +128,6 @@ class ClientImpl : public IClient {
     std::condition_variable init_waiter_;
 
     data_sources::DataSourceStatusManager status_manager_;
-    flag_manager::FlagManager flag_manager_;
-    flag_manager::FlagUpdater flag_updater_;
 
     std::thread thread_;