async_disconnect will close the connection regardless of the current connection state

Summary: related to T13761

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D28057

include/async_mqtt5/impl/disconnect_op.hpp

@@ -2,7 +2,10 @@
 #define ASYNC_MQTT5_DISCONNECT_OP_HPP
 
 #include <boost/asio/consign.hpp>
+#include <boost/asio/deferred.hpp>
 #include <boost/asio/prepend.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <boost/asio/experimental/parallel_group.hpp>
 
 #include <async_mqtt5/types.hpp>
 
@@ -45,7 +48,13 @@ public:
 		_svc_ptr(svc_ptr),
 		_context(std::move(context)),
 		_handler(std::move(handler), _svc_ptr->get_executor())
-	{}
+	{
+		auto slot = asio::get_associated_cancellation_slot(_handler);
+		if (slot.is_connected())
+			slot.assign([&svc = *_svc_ptr](asio::cancellation_type_t) {
+				svc.cancel();
+			});
+	}
 
 	disconnect_op(disconnect_op&&) noexcept = default;
 	disconnect_op(const disconnect_op&) = delete;
@@ -146,10 +155,88 @@ private:
 	}
 };
 
+template <typename ClientService, typename Handler>
+class terminal_disconnect_op {
+	using client_service = ClientService;
+
+	static constexpr uint8_t seconds = 5;
+
+	std::shared_ptr<client_service> _svc_ptr;
+	std::unique_ptr<asio::steady_timer> _timer;
+
+	using handler_type = cancellable_handler<
+		Handler, typename ClientService::executor_type
+	>;
+	handler_type _handler;
+
+public:
+	terminal_disconnect_op(
+		const std::shared_ptr<client_service>& svc_ptr,
+		Handler&& handler
+	) :
+		_svc_ptr(svc_ptr),
+		_timer(new asio::steady_timer(_svc_ptr->get_executor())),
+		_handler(std::move(handler), _svc_ptr->get_executor())
+	{}
+
+	terminal_disconnect_op(terminal_disconnect_op&&) noexcept = default;
+	terminal_disconnect_op(const terminal_disconnect_op&) = delete;
+
+	using executor_type = asio::associated_executor_t<handler_type>;
+	executor_type get_executor() const noexcept {
+		return asio::get_associated_executor(_handler);
+	}
+
+	using allocator_type = asio::associated_allocator_t<handler_type>;
+	allocator_type get_allocator() const noexcept {
+		return asio::get_associated_allocator(_handler);
+	}
+
+	using cancellation_slot_type = asio::associated_cancellation_slot_t<handler_type>;
+	cancellation_slot_type get_cancellation_slot() const noexcept {
+		return asio::get_associated_cancellation_slot(_handler);
+	}
+
+	template <typename DisconnectContext>
+	void perform(DisconnectContext&& context) {
+		namespace asioex = boost::asio::experimental;
+
+		auto init_disconnect = [](
+			auto handler, disconnect_ctx ctx,
+			const std::shared_ptr<ClientService>& svc_ptr
+		) {
+			disconnect_op {
+				svc_ptr, std::move(ctx), std::move(handler)
+			}.perform();
+		};
+
+		_timer->expires_after(std::chrono::seconds(seconds));
+
+		auto timed_disconnect = asioex::make_parallel_group(
+			asio::async_initiate<const asio::deferred_t, void (error_code)>(
+				init_disconnect, asio::deferred,
+				std::forward<DisconnectContext>(context), _svc_ptr
+			),
+			_timer->async_wait(asio::deferred)
+		);
+
+		timed_disconnect.async_wait(
+			asioex::wait_for_one(), asio::prepend(std::move(*this))
+		);
+	}
+
+	void operator()(
+		std::array<std::size_t, 2> /* ord */,
+		error_code disconnect_ec, error_code /* timer_ec */
+	) {
+		_handler.complete(disconnect_ec);
+	}
+};
+
 template <typename ClientService, typename CompletionToken>
 decltype(auto) async_disconnect(
 	disconnect_rc_e reason_code, const disconnect_props& props,
-	bool terminal, const std::shared_ptr<ClientService>& svc_ptr,
+	const std::shared_ptr<ClientService>& svc_ptr,
 	CompletionToken&& token
 ) {
 	using Signature = void (error_code);
@@ -165,11 +252,34 @@ decltype(auto) async_disconnect(
 
 	return asio::async_initiate<CompletionToken, Signature>(
 		initiation, token,
-		disconnect_ctx { reason_code, props, terminal },
+		disconnect_ctx { reason_code, props, false },
 		svc_ptr
 	);
 }
 
+template <typename ClientService, typename CompletionToken>
+decltype(auto) async_terminal_disconnect(
+	disconnect_rc_e reason_code, const disconnect_props& props,
+	const std::shared_ptr<ClientService>& svc_ptr,
+	CompletionToken&& token
+) {
+	using Signature = void (error_code);
+
+	auto initiation = [](
+		auto handler, disconnect_ctx ctx,
+		const std::shared_ptr<ClientService>& svc_ptr
+	) {
+		terminal_disconnect_op {
+			svc_ptr, std::move(handler)
+		}.perform(std::move(ctx));
+	};
+
+	return asio::async_initiate<CompletionToken, Signature>(
+		initiation, token,
+		disconnect_ctx { reason_code, props, true },
+		svc_ptr
+	);
+}
 
 } // end namespace async_mqtt5::detail
 

include/async_mqtt5/impl/publish_rec_op.hpp

@@ -191,7 +191,7 @@ private:
 		props[prop::reason_string] = reason;
 		return async_disconnect(
 			disconnect_rc_e::malformed_packet, props,
-			false, _svc_ptr, asio::detached
+			_svc_ptr, asio::detached
 		);
 	}
 

include/async_mqtt5/impl/publish_send_op.hpp

@@ -400,7 +400,7 @@ private:
 		auto props = disconnect_props {};
 		props[prop::reason_string] = reason;
 		async_disconnect(
-			disconnect_rc_e::malformed_packet, props, false, _svc_ptr,
+			disconnect_rc_e::malformed_packet, props, _svc_ptr,
 			asio::detached
 		);
 	}

include/async_mqtt5/impl/re_auth_op.hpp

@@ -125,7 +125,7 @@ private:
 		auto props = disconnect_props {};
 		props[prop::reason_string] = std::move(message);
 
-		async_disconnect(reason, props, false, _svc_ptr, asio::detached);
+		async_disconnect(reason, props, _svc_ptr, asio::detached);
 	}
 
 };

include/async_mqtt5/impl/read_message_op.hpp

@@ -127,7 +127,7 @@ private:
 		auto svc_ptr = _svc_ptr; // copy before this is moved
 
 		async_disconnect(
-			disconnect_rc_e::malformed_packet, props, false, svc_ptr,
+			disconnect_rc_e::malformed_packet, props, svc_ptr,
 			asio::prepend(std::move(*this), on_disconnect {})
 		);
 	}

include/async_mqtt5/impl/sentry_op.hpp

@@ -70,7 +70,7 @@ public:
 			props[prop::reason_string] = "No reply received within 20 seconds";
 			auto svc_ptr = _svc_ptr;
 			return async_disconnect(
-				disconnect_rc_e::unspecified_error, props, false, svc_ptr,
+				disconnect_rc_e::unspecified_error, props, svc_ptr,
 				asio::prepend(std::move(*this), on_disconnect {})
 			);
 		}

include/async_mqtt5/impl/subscribe_op.hpp

@@ -255,7 +255,7 @@ private:
 		auto props = disconnect_props {};
 		props[prop::reason_string] = reason;
 		async_disconnect(
-			disconnect_rc_e::malformed_packet, props, false, _svc_ptr,
+			disconnect_rc_e::malformed_packet, props, _svc_ptr,
 			asio::detached
 		);
 	}

include/async_mqtt5/impl/unsubscribe_op.hpp

@@ -200,7 +200,7 @@ private:
 		auto props = disconnect_props {};
 		props[prop::reason_string] = reason;
 		async_disconnect(
-			disconnect_rc_e::malformed_packet, props, false, _svc_ptr,
+			disconnect_rc_e::malformed_packet, props, _svc_ptr,
 			asio::detached
 		);
 	}

include/async_mqtt5/mqtt_client.hpp

@@ -806,16 +806,14 @@ public:
 	 * \brief Disconnect the Client by sending a \__DISCONNECT\__ packet
 	 * with a specified Reason Code. This function has terminal effects.
 	 *
-	 * \details Send a \__DISCONNECT\__ packet to the Broker with a Reason Code
-	 * describing the reason for disconnection.
+	 * \details The Client will attempt to send a \__DISCONNECT\__ packet to the Broker
+	 * with a Reason Code describing the reason for disconnection.
+	 * If the \__DISCONNECT\__ packet is successfully transmitted,
+	 * or if `5 seconds` elapsed without a successful send, the Client will terminate the connection.
 	 *
 	 * \attention This function has terminal effects and will close the Client.
 	 * See \ref mqtt_client::cancel.
 	 *
-	 * \note If you wish to close the Client regardless of its state,
-	 * prefer calling the \ref cancel function instead. This function will only
-	 * take effect when the connection has been successfully established.
-	 *
 	 * \param reason_code Reason Code to notify
 	 * the Broker of the reason for disconnection.
 	 * \param props An instance of \__DISCONNECT_PROPS\__.
@@ -841,7 +839,10 @@ public:
 	 *	\par Error codes
 	 *	The list of all possible error codes that this operation can finish with:\n
 	 *		- `boost::system::errc::errc_t::success`\n
-	 *		- `boost::asio::error::operation_aborted`\n
+	 *		- `boost::asio::error::operation_aborted`[footnote
+				This error code can appear if the Client failed to send the \__DISCONNECT\__ packet to the Server.
+				Regardless, the connection to the Server is terminated, and the Client is cancelled.
+			]\n
 	 *		- \link async_mqtt5::client::error::malformed_packet \endlink
 	 *
 	 * Refer to the section on \__ERROR_HANDLING\__ to find the underlying causes for each error code.
@@ -853,10 +854,9 @@ public:
 	) {
 		auto impl = _impl;
 		_impl = impl->dup();
-		return detail::async_disconnect(
+		return detail::async_terminal_disconnect(
 			detail::disconnect_rc_e(static_cast<uint8_t>(reason_code)),
-			props, true, impl,
-			std::forward<CompletionToken>(token)
+			props, impl, std::forward<CompletionToken>(token)
 		);
 	}