feed_pool.h

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#pragma once
#include "imr/mold/packet_builder.h"
#include "imr/mold/retransmission/feed.h"
#include "imr/mold/retransmission_buffer.h"
#include <sys/eventfd.h>
#include <vector>
#include <thread>
namespace imr::mold::retransmission
{
    /** Owns N (`num_feeds`) retransmission feeds.
     *
     * Each feed runs own event loop in dedicated thread.
     * All feeds share a single eventfd used to signal shutdown (via `stop()`)
     */
    class FeedPool
    {
      public:
        /** Constructs and starts `num_feeds` retransmission feeds in their own threads.
         *
         * Each thread construct an instance of `imr::mold::retransmission::Feed` and then starts it immediately.
         *
         * @throws std::system_error if the shutdown eventfd fails to be created.
         */
        FeedPool(std::size_t num_feeds,
                 const Feed::Config& feed_cfg,
                 const PacketBuilder::Config& packet_builder_cfg,
                 std::span<const char> file,
                 const RetransmissionBuffer& retransmission_buffer);
        /** Signals all feed threads to stop by writing to the shared shutdown_fd_.
         *
         *  This is async so retransmission feeds meaning retransmission feeds might finish requests in their epoll set before
         *  receiving the shutdown signal
         *
         *  @throws std::system_error if write() to shutdown_fd_ fails.
         */
        void stop() const;
 
      private:
        util::FileDescriptor shutdown_fd_{[] { return eventfd(0, EFD_CLOEXEC); }};
        std::vector<std::jthread> feeds_;
        // we have to store these as members otherwise have to copy them N times in constructor
        // (if we pass reference from constructor then it can go out of scope before threads have finished using them)
        const Feed::Config* feed_cfg_;
        const PacketBuilder::Config* packet_builder_cfg_;
    };
}