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feat: add FDv1AdapterSynchronizer wrapping IDataSynchronizer as IFDv2Synchronizer
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‎libs/server-sdk/src/CMakeLists.txt‎

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@@ -69,6 +69,8 @@ target_sources(${LIBNAME}
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data_systems/fdv2/source_manager.cpp
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data_systems/fdv2/fdv2_data_system.hpp
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data_systems/fdv2/fdv2_data_system.cpp
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data_systems/fdv2/fdv1_adapter_synchronizer.hpp
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data_systems/fdv2/fdv1_adapter_synchronizer.cpp
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data_systems/background_sync/sources/streaming/streaming_data_source.hpp
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data_systems/background_sync/sources/streaming/streaming_data_source.cpp
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data_systems/background_sync/sources/streaming/event_handler.hpp

‎libs/server-sdk/src/data_systems/fdv2/fdv1_adapter_synchronizer.cpp‎

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#include "fdv1_adapter_synchronizer.hpp"
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#include <utility>
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namespace launchdarkly::server_side::data_systems {
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using data_interfaces::FDv2SourceResult;
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// ----- State -----
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bool FDv1AdapterSynchronizer::State::TryStart() {
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std::lock_guard lock(mutex_);
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if (started_ || closed_) {
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return false;
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}
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started_ = true;
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return true;
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}
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bool FDv1AdapterSynchronizer::State::MarkClosed() {
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std::lock_guard lock(mutex_);
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closed_ = true;
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return started_;
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}
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async::Future<FDv2SourceResult> FDv1AdapterSynchronizer::State::GetNext() {
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std::lock_guard lock(mutex_);
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if (!result_queue_.empty()) {
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auto result = std::move(result_queue_.front());
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result_queue_.pop_front();
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return async::MakeFuture(std::move(result));
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}
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return pending_promise_.emplace().GetFuture();
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}
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void FDv1AdapterSynchronizer::State::ResolvePendingAsShutdown() {
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std::optional<async::Promise<FDv2SourceResult>> promise;
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{
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std::lock_guard lock(mutex_);
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if (pending_promise_) {
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promise = std::move(pending_promise_);
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pending_promise_.reset();
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}
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}
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if (promise) {
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promise->Resolve(FDv2SourceResult{FDv2SourceResult::Shutdown{}});
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}
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}
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void FDv1AdapterSynchronizer::State::Notify(FDv2SourceResult result) {
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std::optional<async::Promise<FDv2SourceResult>> promise;
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{
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std::lock_guard lock(mutex_);
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if (closed_) {
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return;
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}
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if (pending_promise_) {
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promise = std::move(pending_promise_);
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pending_promise_.reset();
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} else {
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result_queue_.push_back(std::move(result));
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return;
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}
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}
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// Resolve outside the lock — Promise::Resolve may invoke inline
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// continuations that could call back into Notify or GetNext.
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promise->Resolve(std::move(result));
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}
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// ----- ConvertingDestination -----
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FDv1AdapterSynchronizer::ConvertingDestination::ConvertingDestination(
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std::weak_ptr<State> state)
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: state_(std::move(state)) {}
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void FDv1AdapterSynchronizer::ConvertingDestination::Init(
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data_model::SDKDataSet data_set) {
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auto state = state_.lock();
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if (!state) {
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return;
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}
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data_interfaces::ChangeSetData changes;
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changes.reserve(data_set.flags.size() + data_set.segments.size());
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for (auto& [key, flag] : data_set.flags) {
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changes.push_back({key, std::move(flag)});
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}
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for (auto& [key, segment] : data_set.segments) {
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changes.push_back({key, std::move(segment)});
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}
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state->Notify(FDv2SourceResult{FDv2SourceResult::ChangeSet{
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data_model::ChangeSet<data_interfaces::ChangeSetData>{
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data_model::ChangeSetType::kFull, std::move(changes),
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data_model::Selector{}}}});
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}
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void FDv1AdapterSynchronizer::ConvertingDestination::Upsert(
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std::string const& key,
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data_model::FlagDescriptor flag) {
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auto state = state_.lock();
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if (!state) {
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return;
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}
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data_interfaces::ChangeSetData changes;
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changes.push_back({key, std::move(flag)});
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state->Notify(FDv2SourceResult{FDv2SourceResult::ChangeSet{
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data_model::ChangeSet<data_interfaces::ChangeSetData>{
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data_model::ChangeSetType::kPartial, std::move(changes),
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data_model::Selector{}}}});
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}
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void FDv1AdapterSynchronizer::ConvertingDestination::Upsert(
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std::string const& key,
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data_model::SegmentDescriptor segment) {
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auto state = state_.lock();
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if (!state) {
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return;
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}
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data_interfaces::ChangeSetData changes;
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changes.push_back({key, std::move(segment)});
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state->Notify(FDv2SourceResult{FDv2SourceResult::ChangeSet{
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data_model::ChangeSet<data_interfaces::ChangeSetData>{
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data_model::ChangeSetType::kPartial, std::move(changes),
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data_model::Selector{}}}});
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}
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std::string const& FDv1AdapterSynchronizer::ConvertingDestination::Identity()
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const {
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static std::string const identity = "FDv1 adapter destination";
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return identity;
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}
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// ----- FDv1AdapterSynchronizer -----
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FDv1AdapterSynchronizer::FDv1AdapterSynchronizer(
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std::unique_ptr<data_interfaces::IDataSynchronizer> fdv1_source)
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: state_(std::make_shared<State>()),
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destination_(std::make_unique<ConvertingDestination>(state_)),
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fdv1_source_(std::move(fdv1_source)) {}
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FDv1AdapterSynchronizer::~FDv1AdapterSynchronizer() {
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Close();
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}
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async::Future<FDv2SourceResult> FDv1AdapterSynchronizer::Next(
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data_model::Selector /*selector*/) {
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auto closed = close_promise_.GetFuture();
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if (closed.IsFinished()) {
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return async::MakeFuture(
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FDv2SourceResult{FDv2SourceResult::Shutdown{}});
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}
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if (state_->TryStart()) {
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fdv1_source_->StartAsync(destination_.get(),
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/*bootstrap_data=*/nullptr);
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}
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auto result_future = state_->GetNext();
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if (result_future.IsFinished()) {
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return result_future;
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}
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return async::WhenAny(closed, result_future)
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.Then(
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[state = state_, result_future](std::size_t const& idx) mutable
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-> async::Future<FDv2SourceResult> {
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if (idx == 0) {
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state->ResolvePendingAsShutdown();
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return async::MakeFuture(
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FDv2SourceResult{FDv2SourceResult::Shutdown{}});
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}
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return result_future;
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},
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async::kInlineExecutor);
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}
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void FDv1AdapterSynchronizer::Close() {
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if (!close_promise_.Resolve(std::monostate{})) {
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return;
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}
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if (state_->MarkClosed()) {
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fdv1_source_->ShutdownAsync([] {});
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}
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}
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std::string const& FDv1AdapterSynchronizer::Identity() const {
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static std::string const identity = "FDv1 fallback adapter";
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return identity;
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}
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} // namespace launchdarkly::server_side::data_systems

‎libs/server-sdk/src/data_systems/fdv2/fdv1_adapter_synchronizer.hpp‎

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#pragma once
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#include "../../data_interfaces/destination/idestination.hpp"
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#include "../../data_interfaces/source/idata_synchronizer.hpp"
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#include "../../data_interfaces/source/ifdv2_synchronizer.hpp"
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#include <launchdarkly/async/promise.hpp>
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#include <deque>
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#include <memory>
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#include <mutex>
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#include <optional>
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#include <string>
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#include <variant>
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namespace launchdarkly::server_side::data_systems {
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/**
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* Adapts an FDv1 IDataSynchronizer to the IFDv2Synchronizer interface.
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*
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* FDv1 Init/Upsert callbacks delivered through an internal IDestination are
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* translated into FDv2SourceResult::ChangeSet results, with empty selectors
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* and fdv1_fallback = false (the directive does not re-fire from FDv1 data).
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*
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* Threading: Next() and Close() may be called from any thread; only one
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* Next() may be outstanding at a time. The adapter blocks in its destructor
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* waiting for the FDv1 source's ShutdownAsync completion, so no callbacks
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* are in flight when the wrapped source is destroyed.
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*/
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class FDv1AdapterSynchronizer final
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: public data_interfaces::IFDv2Synchronizer {
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public:
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explicit FDv1AdapterSynchronizer(
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std::unique_ptr<data_interfaces::IDataSynchronizer> fdv1_source);
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~FDv1AdapterSynchronizer() override;
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async::Future<data_interfaces::FDv2SourceResult> Next(
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data_model::Selector selector) override;
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void Close() override;
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[[nodiscard]] std::string const& Identity() const override;
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private:
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/**
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* Holds the lifecycle, result queue, and pending Next() promise; shared
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* with the FDv1 source's IDestination via the inner ConvertingDestination.
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* All methods are thread-safe.
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*/
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class State {
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public:
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// Returns true if this call transitioned Initial → Started; false if
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// already started or already closed. Used to gate the one-time
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// StartAsync call on the wrapped FDv1 source.
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bool TryStart();
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// Marks the state closed and returns whether the source was started
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// before the transition (so the caller knows whether ShutdownAsync
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// needs to be called).
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bool MarkClosed();
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async::Future<data_interfaces::FDv2SourceResult> GetNext();
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// Resolves any pending Next() promise with Shutdown and clears it.
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// Called on the close path so the abandoned promise doesn't leave
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// potential continuations dangling.
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void ResolvePendingAsShutdown();
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void Notify(data_interfaces::FDv2SourceResult result);
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private:
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// Protected by mutex_.
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mutable std::mutex mutex_;
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bool started_ = false;
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bool closed_ = false;
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std::optional<async::Promise<data_interfaces::FDv2SourceResult>>
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pending_promise_;
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std::deque<data_interfaces::FDv2SourceResult> result_queue_;
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};
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/**
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* Translates FDv1 IDestination callbacks into FDv2 results queued on
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* State. Thread-safe (delegates to State).
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*/
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class ConvertingDestination final : public data_interfaces::IDestination {
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public:
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explicit ConvertingDestination(std::weak_ptr<State> state);
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void Init(data_model::SDKDataSet data_set) override;
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void Upsert(std::string const& key,
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data_model::FlagDescriptor flag) override;
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void Upsert(std::string const& key,
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data_model::SegmentDescriptor segment) override;
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[[nodiscard]] std::string const& Identity() const override;
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private:
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std::weak_ptr<State> state_;
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};
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// const after construction.
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std::shared_ptr<State> const state_;
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std::unique_ptr<ConvertingDestination> const destination_;
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std::unique_ptr<data_interfaces::IDataSynchronizer> const fdv1_source_;
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// Thread-safe primitive.
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async::Promise<std::monostate> close_promise_;
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};
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} // namespace launchdarkly::server_side::data_systems

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