Alex-PLACET commented on code in PR #50407: URL: https://github.com/apache/arrow/pull/50407#discussion_r4324130621
########## cpp/src/arrow/flight/transport_server_internal.h: ########## @@ -0,0 +1,303 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#pragma once + +#include <atomic> +#include <chrono> +#include <memory> +#include <thread> +#include <utility> +#include <vector> + +#include "arrow/flight/platform.h" +#include "arrow/flight/server.h" +#include "arrow/flight/visibility.h" +#include "arrow/result.h" +#include "arrow/status.h" +#include "arrow/util/io_util.h" +#include "arrow/util/logging.h" +#include "arrow/util/uri.h" + +namespace arrow::flight::internal { + +class ServerDataStream; +class PeekableFlightDataReader; + +/// \brief Adapt TransportDataStream to the FlightMessageReader +/// interface for DoPut. +class TransportMessageReader final : public FlightMessageReader { + public: + TransportMessageReader(ServerDataStream* stream, + std::shared_ptr<MemoryManager> memory_manager); + + Status Init(); + + const FlightDescriptor& descriptor() const override; + + arrow::Result<std::shared_ptr<Schema>> GetSchema() override; + + arrow::Result<FlightStreamChunk> Next() override; + + ipc::ReadStats stats() const override; + + private: + /// Ensure we are set up to read data. + Status EnsureDataStarted(); + + FlightDescriptor descriptor_; + std::shared_ptr<PeekableFlightDataReader> peekable_reader_; + std::shared_ptr<MemoryManager> memory_manager_; + std::shared_ptr<ipc::RecordBatchStreamReader> batch_reader_; + std::shared_ptr<Buffer> app_metadata_; +}; + +/// \brief A writer for IPC payloads to a ServerDataStream. +class TransportMessageWriter final : public FlightMessageWriter { + public: + explicit TransportMessageWriter(ServerDataStream* stream); + + Status Begin(const std::shared_ptr<Schema>& schema, + const ipc::IpcWriteOptions& options) override; + + Status WriteRecordBatch(const RecordBatch& batch) override; + + Status WriteMetadata(std::shared_ptr<Buffer> app_metadata) override; + + Status WriteWithMetadata(const RecordBatch& batch, + std::shared_ptr<Buffer> app_metadata) override; + + Status Close() override; + + ipc::WriteStats stats() const override; + + private: + Status CheckStarted(); + + ServerDataStream* stream_; + std::unique_ptr<ipc::RecordBatchWriter> batch_writer_; + std::shared_ptr<Buffer> app_metadata_; + ::arrow::ipc::IpcWriteOptions ipc_options_; +}; + +/// \brief A writer for application-defined metadata to a ServerDataStream. +class TransportMetadataWriter final : public FlightMetadataWriter { + public: + explicit TransportMetadataWriter(ServerDataStream* stream); + + Status WriteMetadata(const Buffer& buffer) override; + + private: + ServerDataStream* stream_; +}; + +/// \brief Write a FlightDataStream to a transport-level stream. +/// +/// Used by DoGet and DoExchange to stream results back to the client. +/// The schema is written first, followed by record batches until the +/// stream is exhausted. +/// +/// \param[in] data_stream The Arrow data stream to read from. +/// \param[in] stream The transport-specific data stream to write to. +Status WriteDataStream(std::unique_ptr<FlightDataStream> data_stream, + ServerDataStream* stream); + +/// \brief Manages a background thread that waits for OS signals. +/// +/// Creates a signal-safe SelfPipe and spawns a thread that blocks on it. +/// When a signal is received, the signal handler writes to the SelfPipe +/// to wake the thread. The destructor ensures the thread is joined. +class ServerSignalHandler { + public: + ARROW_DISALLOW_COPY_AND_ASSIGN(ServerSignalHandler); + ServerSignalHandler() = default; + + /// \brief Initialize the signal handler and start the background thread. + /// + /// \param[in] self_pipe The pipe the handler thread should wait on It is + /// stored before the thread is started, so the signal handler can always + /// write to it. + /// \param[in] handler A callable that will be invoked on the background + /// thread, receiving the SelfPipe as an argument. + template <typename Fn> + Status Init(const std::shared_ptr<::arrow::internal::SelfPipe>& self_pipe, + Fn&& handler) { + self_pipe_ = self_pipe; + handle_signals_ = std::thread(std::forward<Fn>(handler), self_pipe_); + return Status::OK(); + } + + /// \brief Shut down the signal handler and join the background thread. + /// + /// The thread is woken with a plain payload rather than SelfPipe::Shutdown(): + /// a signal handler may have been entered and preempted just before this + /// point, and writing to a pipe whose read end was closed raises SIGPIPE in + /// that handler, killing the process. + Status Shutdown() { + self_pipe_->Send(/*payload=*/0); + handle_signals_.join(); + return Status::OK(); + } + + ~ServerSignalHandler() { ARROW_CHECK_OK(Shutdown()); } + + private: + std::shared_ptr<::arrow::internal::SelfPipe> self_pipe_; + std::thread handle_signals_; +}; + +/// \brief Manages signal-driven graceful shutdown for server transports. +/// +/// Installs signal handlers for the given set of signals. When a signal is +/// received, the registered shutdown callback is invoked. Uses a SelfPipe +/// to safely bridge the signal handler (which runs in a restricted context) +/// to a background thread that performs the actual shutdown. +class ARROW_FLIGHT_EXPORT ServerSignalState { + public: + ServerSignalState() = default; + + /// \brief Configure which signals should trigger shutdown. + /// + /// \param[in] sigs List of signal numbers (e.g. SIGINT, SIGTERM). + Status SetShutdownOnSignals(const std::vector<int>& sigs); + /// \brief Return the last signal that was received, or 0 if none. + int GotSignal() const; + + /// \brief Run the server with signal-aware lifecycle management. + /// + /// Installs signal handlers, calls \p wait (which should block until the + /// server stops), and restores original signal handlers on return. + /// If a signal is received during \p wait, \p shutdown is called first. + /// + /// \param[in] wait A callable that blocks until the server stops. + /// \param[in] shutdown A callable invoked on signal receipt to stop the server. + /// \param[in] not_started_message Logged if shutdown is called before the server + /// starts. \param[in] shutdown_warning Logged if shutdown itself fails. + template <typename WaitFn, typename ShutdownFn> + Status Serve(WaitFn&& wait, ShutdownFn&& shutdown, const char* not_started_message, + const char* shutdown_warning) { + got_signal_ = 0; + old_signal_handlers_.clear(); + // Everything the signal handler touches must be initialized before the + // instance is published: a signal arriving earlier would otherwise find an + // empty self-pipe (crash) or an empty shutdown callback, in which case + // WaitForSignals() consumes the wakeup and wait() blocks forever. + ARROW_ASSIGN_OR_RAISE(self_pipe_, + ::arrow::internal::SelfPipe::Make(/*signal_safe=*/true)); + shutdown_ = [shutdown = std::forward<ShutdownFn>(shutdown)]() mutable { + return shutdown(nullptr); + }; + shutdown_warning_ = shutdown_warning; + running_instance_ = this; + + Status status; + { + ServerSignalHandler signal_handler; + status = signal_handler.Init(self_pipe_, &ServerSignalState::WaitForSignals); + if (status.ok()) { + for (size_t i = 0; i < signals_.size(); ++i) { + int signum = signals_[i]; + ::arrow::internal::SignalHandler new_handler(&ServerSignalState::HandleSignal), + old_handler; + auto old = ::arrow::internal::SetSignalHandler(signum, new_handler); + if (!old.ok()) { + status = old.status(); + break; + } + old_signal_handlers_.push_back(std::move(old).ValueOrDie()); + } + } + if (status.ok()) { + status = wait(); + } + // Stop publishing this instance before the signal thread is joined: the + // destructor shuts the self-pipe down, and a signal handler writing to a + // closed pipe would kill the process with SIGPIPE. + running_instance_ = nullptr; + // The signal thread is joined by the destructor here, before the callback + // is cleared below: it may be executing it right now. + } + + shutdown_ = nullptr; + shutdown_warning_ = nullptr; + + // Restore the original handlers, whatever the outcome of wait() was. + Status restore_status; + for (size_t i = 0; i < old_signal_handlers_.size(); ++i) { + auto restored = + ::arrow::internal::SetSignalHandler(signals_[i], old_signal_handlers_[i]); + if (!restored.ok() && restore_status.ok()) { + restore_status = restored.status(); + } + } + if (!status.ok()) { + return status; + } + return restore_status; + } + + /// \brief Shut down the server through the given callback. + /// + /// Clears the running instance pointer, then invokes \p shutdown. + /// + /// \param[in] shutdown A callable that performs the transport-specific shutdown. + /// \param[in] deadline Optional deadline for the shutdown. + template <typename ShutdownFn> + Status Shutdown(ShutdownFn&& shutdown, + const std::chrono::system_clock::time_point* deadline) { + running_instance_ = nullptr; + return shutdown(deadline); + } + + /// \brief Wait for the server to stop without initiating shutdown. + /// + /// \param[in] wait A callable that blocks until the server stops. + template <typename WaitFn> + Status Wait(WaitFn&& wait) { + RETURN_NOT_OK(wait()); + running_instance_ = nullptr; + return Status::OK(); + } + + private: + /// \brief Static entry point for the OS signal handler. + static void HandleSignal(int signum); + + /// \brief Record the received signal and wake the background thread. + void DoHandleSignal(int signum); + + /// \brief Background thread that blocks on the SelfPipe, then invokes shutdown. + static void WaitForSignals(std::shared_ptr<::arrow::internal::SelfPipe> self_pipe); + + // Signal handlers (on Windows) and the shutdown handler (other platforms) + // are executed in a separate thread, so getting the current thread instance + // wouldn't make sense. This means only a single instance can receive signals. + static std::atomic<ServerSignalState*> running_instance_; Review Comment: You are right, I restored it -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
