monero/src/rpc/zmq_pub.h

// Copyright (c) 2020, The Monero Project
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#pragma once

#include <array>
#include <boost/thread/mutex.hpp>
#include <boost/utility/string_ref.hpp>
#include <cstdint>
#include <deque>
#include <memory>
#include <vector>

#include "cryptonote_basic/fwd.h"
#include "net/zmq.h"
#include "span.h"

namespace cryptonote { namespace listener
{
/*! \brief Sends ZMQ PUB messages on cryptonote events

    Clients must ensure that all transaction(s) are notified before any blocks
    they are contained in, and must ensure that each block is notified in chain
    order. An external lock **must** be held by clients during the entire
    txpool check and notification sequence and (a possibly second) lock is held
    during the entire block check and notification sequence. Otherwise, events
    could be sent in a different order than processed. */
class zmq_pub
{
  /* Each socket has its own internal queue. So we can only use one socket, else
     the messages being published are not guaranteed to be in the same order
     pushed. */

    net::zmq::socket relay_;
    std::deque<std::vector<txpool_event>> txes_;
    std::array<std::size_t, 2> chain_subs_;
    std::array<std::size_t, 2> txpool_subs_;
    boost::mutex sync_; //!< Synchronizes counts in `*_subs_` arrays.

  public:
    //! \return Name of ZMQ_PAIR endpoint for pub notifications
    static constexpr const char* relay_endpoint() noexcept { return "inproc://pub_relay"; }

    explicit zmq_pub(void* context);

    zmq_pub(const zmq_pub&) = delete;
    zmq_pub(zmq_pub&&) = delete;

    ~zmq_pub();

    zmq_pub& operator=(const zmq_pub&) = delete;
    zmq_pub& operator=(zmq_pub&&) = delete;

    //! Process a client subscription request (from XPUB sockets). Thread-safe.
    bool sub_request(const boost::string_ref message);

    /*! Forward ZMQ messages sent to `relay` via `send_chain_main` or
      `send_txpool_add` to `pub`. Used by `ZmqServer`. */
    bool relay_to_pub(void* relay, void* pub);

    /*! Send a `ZMQ_PUB` notification for a change to the main chain.
        Thread-safe.
        \return Number of ZMQ messages sent to relay. */
    std::size_t send_chain_main(std::uint64_t height, epee::span<const cryptonote::block> blocks);

    /*! Send a `ZMQ_PUB` notification for new tx(es) being added to the local
        pool. Thread-safe.
        \return Number of ZMQ messages sent to relay. */
    std::size_t send_txpool_add(std::vector<cryptonote::txpool_event> txes);

    //! Callable for `send_chain_main` with weak ownership to `zmq_pub` object.
    struct chain_main
    {
      std::weak_ptr<zmq_pub> self_;
      void operator()(std::uint64_t height, epee::span<const cryptonote::block> blocks) const;
    };

    //! Callable for `send_txpool_add` with weak ownership to `zmq_pub` object.
    struct txpool_add
    {
      std::weak_ptr<zmq_pub> self_;
      void operator()(std::vector<cryptonote::txpool_event> txes) const;
    };
  };
}}