socket_monitor.hpp

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/*
  ____             _        _   __  __             _ _
 / ___|  ___   ___| | _____| |_|  \/  | ___  _ __ (_) |_ ___  _ __
 \___ \ / _ \ / __| |/ / _ \ __| |\/| |/ _ \| '_ \| | __/ _ \| '__|
  ___) | (_) | (__|   <  __/ |_| |  | | (_) | | | | | || (_) | |
 |____/ \___/ \___|_|\_\___|\__|_|  |_|\___/|_| |_|_|\__\___/|_|
 
Wraps zmq_socket_monitor()/zmq::monitor_t so callers can turn connection
lifecycle guesswork into fact: a real ZMQ_EVENT_CONNECTED instead of a blind
sleep, a real ZMQ_EVENT_HANDSHAKE_FAILED_AUTH instead of a bare receive
timeout (ZMQ_DEVELOPMENT.md §2.1). Purely local observation -- nothing on the
wire changes, so using this has no version impact.
 
Author(s): Paolo Bosetti
*/
#pragma once
 
#include <chrono>
#include <cstdint>
#include <memory>
#include <optional>
#include <string>
 
#include <zmq.hpp>
 
namespace Mads {
 
enum class LinkEvent {
  None,
  Connected,
  ConnectDelayed,
  ConnectRetried,
  HandshakeSucceeded,
  HandshakeFailedAuth,
  HandshakeFailedProtocol,
  HandshakeFailedNoDetail,
  Disconnected,
  AcceptFailed,
};
 
enum class LinkStatus {
  Unknown, 
  Up,      
  Down,    
};
 
struct LinkState {
  LinkStatus status = LinkStatus::Unknown;
  LinkEvent last_event = LinkEvent::None;
  LinkEvent last_handshake = LinkEvent::None;
  std::string last_event_address;
  uint64_t drops = 0;
  uint64_t recoveries = 0;
  std::optional<std::chrono::steady_clock::time_point> changed_at;
  int last_event_value = 0;
  uint64_t accept_failures = 0;
};
 
class SocketMonitor {
public:
  SocketMonitor();
  ~SocketMonitor();
  SocketMonitor(const SocketMonitor &) = delete;
  SocketMonitor &operator=(const SocketMonitor &) = delete;
 
  void start(zmq::socket_t &socket, int events = ZMQ_EVENT_ALL);
 
  void attach(zmq::socket_t &socket, int events = ZMQ_EVENT_ALL);
 
  zmq::socket_ref pollable() const;
 
  void process_pending();
 
  void stop();
 
  bool wait_connected(std::chrono::milliseconds timeout);
 
  bool wait_handshake_succeeded(std::chrono::milliseconds timeout);
 
  LinkEvent last_event() const;
 
  LinkState state() const;
 
  std::string last_event_address() const;
 
private:
  class Impl;
  std::unique_ptr<Impl> _impl;
};
 
} // namespace Mads