feat: Implement polling data source. (#28)

Author: kinyoklion

apps/hello-cpp/main.cpp

@@ -3,6 +3,7 @@
 
 #include <boost/asio/io_context.hpp>
 
+#include "config/detail/builders/data_source_builder.hpp"
 #include "console_backend.hpp"
 #include "context_builder.hpp"
 #include "launchdarkly/client_side/data_sources/detail/streaming_data_source.hpp"
@@ -17,6 +18,7 @@ using launchdarkly::Logger;
 using launchdarkly::LogLevel;
 using launchdarkly::client_side::Client;
 using launchdarkly::client_side::ConfigBuilder;
+using launchdarkly::client_side::DataSourceBuilder;
 using launchdarkly::client_side::flag_manager::detail::FlagManager;
 using launchdarkly::client_side::flag_manager::detail::FlagUpdater;
 
@@ -31,11 +33,23 @@ int main() {
         return 1;
     }
 
-    Client client(ConfigBuilder(key).Build().value(),
-                  ContextBuilder().kind("user", "ryan").build());
+    Client client(
+        ConfigBuilder(key)
+            .DataSource(DataSourceBuilder()
+                            .Method(DataSourceBuilder::Polling().PollInterval(
+                                std::chrono::seconds{30}))
+                            .WithReasons(true)
+                            .UseReport(true))
+            .Build()
+            .value(),
+        ContextBuilder().kind("user", "ryan").build());
 
     client.WaitForReadySync(std::chrono::seconds(30));
 
     auto value = client.BoolVariation("my-boolean-flag", false);
     LD_LOG(logger, LogLevel::kInfo) << "Value was: " << value;
+
+    // Sit around.
+    std::cout << "Press enter to exit" << std::endl;
+    std::cin.get();
 }

libs/client-sdk/include/launchdarkly/client_side/data_sources/data_source_status.hpp

@@ -10,6 +10,7 @@
 
 #include "launchdarkly/client_side/connection.hpp"
 #include "launchdarkly/client_side/data_sources/data_source_status.hpp"
+#include "network/detail/http_requester.hpp"
 
 namespace launchdarkly::client_side::data_sources {
 
@@ -79,7 +80,7 @@ class DataSourceStatus {
      */
     class ErrorInfo {
        public:
-        using StatusCodeType = int32_t;
+        using StatusCodeType = network::detail::HttpResult::StatusCode;
 
         /**
          * An enumeration describing the general type of an error.

libs/client-sdk/include/launchdarkly/client_side/data_sources/detail/streaming_data_handler.hpp renamed to libs/client-sdk/include/launchdarkly/client_side/data_sources/detail/data_source_event_handler.hpp

@@ -8,16 +8,18 @@
 #include "launchdarkly/client_side/data_source.hpp"
 #include "launchdarkly/client_side/data_source_update_sink.hpp"
 #include "launchdarkly/client_side/data_sources/detail/data_source_status_manager.hpp"
-#include "launchdarkly/sse/client.hpp"
 #include "logger.hpp"
 
 namespace launchdarkly::client_side::data_sources::detail {
 
 /**
- * This class handles events source events, parses them, and then uses
+ * This class handles LaunchDarkly events, parses them, and then uses
  * a IDataSourceUpdateSink to process the parsed events.
+ *
+ * This can be used for streaming or for polling. For polling only "put" events
+ * will be used.
  */
-class StreamingDataHandler {
+class DataSourceEventHandler {
    public:
     /**
      * Status indicating if the message was processed, or if there
@@ -45,16 +47,18 @@ class StreamingDataHandler {
         uint64_t version;
     };
 
-    StreamingDataHandler(IDataSourceUpdateSink* handler,
-                         Logger const& logger,
-                         DataSourceStatusManager& status_manager);
+    DataSourceEventHandler(IDataSourceUpdateSink* handler,
+                           Logger const& logger,
+                           DataSourceStatusManager& status_manager);
 
     /**
-     * Handle an SSE event.
-     * @param event The event to handle.
+     * Handles an event from the LaunchDarkly service.
+     * @param type The type of the event. "put"/"patch"/"delete".
+     * @param data The content of the evnet.
      * @return A status indicating if the message could be handled.
      */
-    MessageStatus HandleMessage(launchdarkly::sse::Event const& event);
+    MessageStatus HandleMessage(std::string const& type,
+                                std::string const& data);
 
    private:
     IDataSourceUpdateSink* handler_;

libs/client-sdk/include/launchdarkly/client_side/data_sources/detail/data_source_status_manager.hpp

@@ -25,6 +25,30 @@ class DataSourceStatusManager : public IDataSourceStatusProvider {
      */
     void SetState(DataSourceStatus::DataSourceState state);
 
+    /**
+     * If an error and state change happen simultaneously, then they should
+     * be updated simultaneously.
+     *
+     * @param state The new state.
+     * @param code Status code for an http error.
+     * @param message The message to associate with the error.
+     */
+    void SetState(DataSourceStatus::DataSourceState state,
+                  DataSourceStatus::ErrorInfo::StatusCodeType code,
+                  std::string message);
+
+    /**
+     * If an error and state change happen simultaneously, then they should
+     * be updated simultaneously.
+     *
+     * @param state The new state.
+     * @param kind The error kind.
+     * @param message The message to associate with the error.
+     */
+    void SetState(DataSourceStatus::DataSourceState state,
+                  DataSourceStatus::ErrorInfo::ErrorKind kind,
+                  std::string message);
+
     /**
      * Set an error with the given kind and message.
      *
@@ -42,7 +66,8 @@ class DataSourceStatusManager : public IDataSourceStatusProvider {
      * Set an error based on the given status code.
      * @param code The status code of the error.
      */
-    void SetError(DataSourceStatus::ErrorInfo::StatusCodeType code);
+    void SetError(DataSourceStatus::ErrorInfo::StatusCodeType code,
+                  std::string message);
     // TODO: Handle error codes once the EventSource supports it.
 
     DataSourceStatus Status() override;
@@ -61,6 +86,7 @@ class DataSourceStatusManager : public IDataSourceStatusProvider {
     boost::signals2::signal<void(data_sources::DataSourceStatus status)>
         data_source_status_signal_;
     mutable std::mutex status_mutex_;
+    bool UpdateState(DataSourceStatus::DataSourceState const& requested_state);
 };
 
 }  // namespace launchdarkly::client_side::data_sources::detail

libs/client-sdk/include/launchdarkly/client_side/data_sources/detail/polling_data_source.hpp

@@ -0,0 +1,51 @@
+#pragma once
+
+#include <chrono>
+
+#include <boost/asio/any_io_executor.hpp>
+
+#include "config/client.hpp"
+#include "config/detail/built/http_properties.hpp"
+#include "data_source_status_manager.hpp"
+#include "launchdarkly/client_side/data_source.hpp"
+#include "launchdarkly/client_side/data_source_update_sink.hpp"
+#include "launchdarkly/client_side/data_sources/detail/data_source_event_handler.hpp"
+#include "logger.hpp"
+#include "network/detail/asio_requester.hpp"
+
+namespace launchdarkly::client_side::data_sources::detail {
+
+class PollingDataSource : public IDataSource {
+   public:
+    PollingDataSource(Config const& config,
+                      boost::asio::any_io_executor ioc,
+                      Context const& context,
+                      IDataSourceUpdateSink* handler,
+                      DataSourceStatusManager& status_manager,
+                      Logger const& logger);
+
+    void Start() override;
+    void Close() override;
+
+   private:
+    void DoPoll();
+
+    std::string string_context_;
+    DataSourceStatusManager& status_manager_;
+    DataSourceEventHandler data_source_handler_;
+    std::string polling_endpoint_;
+
+    network::detail::AsioRequester requester_;
+    Logger const& logger_;
+    boost::asio::any_io_executor ioc_;
+    std::chrono::seconds polling_interval_;
+    network::detail::HttpRequest request_;
+    std::optional<std::string> etag_;
+
+    boost::asio::steady_timer timer_;
+    std::chrono::time_point<std::chrono::system_clock> last_poll_start_;
+
+    void StartPollingTimer();
+};
+
+}  // namespace launchdarkly::client_side::data_sources::detail

libs/client-sdk/include/launchdarkly/client_side/data_sources/detail/streaming_data_source.hpp

@@ -5,45 +5,39 @@ using namespace std::chrono_literals;
 
 #include <boost/asio/any_io_executor.hpp>
 
+#include "config/client.hpp"
 #include "config/detail/built/http_properties.hpp"
 #include "config/detail/built/service_endpoints.hpp"
 #include "context.hpp"
 #include "data/evaluation_result.hpp"
 #include "launchdarkly/client_side/data_source.hpp"
 #include "launchdarkly/client_side/data_source_update_sink.hpp"
+#include "launchdarkly/client_side/data_sources/detail/data_source_event_handler.hpp"
 #include "launchdarkly/client_side/data_sources/detail/data_source_status_manager.hpp"
-#include "launchdarkly/client_side/data_sources/detail/streaming_data_handler.hpp"
 #include "launchdarkly/sse/client.hpp"
 #include "logger.hpp"
 
 namespace launchdarkly::client_side::data_sources::detail {
 
 class StreamingDataSource final : public IDataSource {
    public:
-    StreamingDataSource(
-        std::string const& sdk_key,
-        boost::asio::any_io_executor ioc,
-        Context const& context,
-        config::detail::built::ServiceEndpoints const& endpoints,
-        config::detail::built::HttpProperties const& http_properties,
-        bool use_report,
-        bool with_reasons,
-        IDataSourceUpdateSink* handler,
-        DataSourceStatusManager& status_manager,
-        Logger const& logger);
+    StreamingDataSource(Config const& config,
+                        boost::asio::any_io_executor ioc,
+                        Context const& context,
+                        IDataSourceUpdateSink* handler,
+                        DataSourceStatusManager& status_manager,
+                        Logger const& logger);
 
     void Start() override;
     void Close() override;
 
    private:
     DataSourceStatusManager& status_manager_;
-    StreamingDataHandler data_source_handler_;
+    DataSourceEventHandler data_source_handler_;
     std::string streaming_endpoint_;
     std::string string_context_;
 
     Logger const& logger_;
     std::shared_ptr<launchdarkly::sse::Client> client_;
-
-    inline static const std::string streaming_path_ = "/meval";
 };
 }  // namespace launchdarkly::client_side::data_sources::detail

libs/client-sdk/src/CMakeLists.txt

@@ -15,8 +15,9 @@ add_library(${LIBNAME}
         ${HEADER_LIST}
         data_sources/streaming_data_source.cpp
         data_sources/base_64.cpp
-        data_sources/streaming_data_handler.cpp
+        data_sources/data_source_event_handler.cpp
         data_source_update_sink.cpp
+        data_sources/polling_data_source.cpp
         flag_manager/flag_manager.cpp
         flag_manager/flag_updater.cpp
         flag_manager/flag_change_event.cpp

libs/client-sdk/src/api.cpp

@@ -4,12 +4,32 @@
 #include <utility>
 
 #include "events/detail/asio_event_processor.hpp"
+#include "launchdarkly/client_side/data_sources/detail/polling_data_source.hpp"
 #include "launchdarkly/client_side/data_sources/detail/streaming_data_source.hpp"
 
 namespace launchdarkly::client_side {
 
 using launchdarkly::client_side::data_sources::DataSourceStatus;
 
+static std::unique_ptr<IDataSource> MakeDataSource(
+    Config const& config,
+    Context const& context,
+    boost::asio::any_io_executor executor,
+    flag_manager::detail::FlagUpdater& flag_updater,
+    data_sources::detail::DataSourceStatusManager& status_manager,
+    Logger& logger) {
+    if (config.DataSourceConfig().method.which() == 0) {
+        // TODO: use initial reconnect delay.
+        return std::make_unique<launchdarkly::client_side::data_sources::
+                                    detail::StreamingDataSource>(
+            config, executor, context, &flag_updater, status_manager, logger);
+    } else {
+        return std::make_unique<
+            launchdarkly::client_side::data_sources::detail::PollingDataSource>(
+            config, executor, context, &flag_updater, status_manager, logger);
+    }
+}
+
 Client::Client(Config config, Context context)
     : logger_(config.Logger()),
       context_(std::move(context)),
@@ -21,19 +41,12 @@ Client::Client(Config config, Context context)
               config.SdkKey(),
               logger_)),
       flag_updater_(flag_manager_),
-      // TODO: Support polling.
-      data_source_(std::make_unique<launchdarkly::client_side::data_sources::
-                                        detail::StreamingDataSource>(
-          config.SdkKey(),
-          ioc_.get_executor(),
-          context_,
-          config.ServiceEndpoints(),
-          config.HttpProperties(),
-          config.DataSourceConfig().use_report,
-          config.DataSourceConfig().with_reasons,
-          &flag_updater_,
-          status_manager_,
-          logger_)),
+      data_source_(MakeDataSource(config,
+                                  context_,
+                                  ioc_.get_executor(),
+                                  flag_updater_,
+                                  status_manager_,
+                                  logger_)),
       initialized_(false) {
     data_source_->Start();