HttpServerConnection: Don't spawn useless coroutines

Currently, for each `Disconnect()` call, we spawn a coroutine, but every
one of them is just usesless, except the first one. Thus, we should not
spawn a coroutine if someone has already triggered a disconnect.

lib/remote/httpserverconnection.cpp

@@ -72,12 +72,10 @@ void HttpServerConnection::Disconnect()
 {
 	namespace asio = boost::asio;
 
-	HttpServerConnection::Ptr keepAlive (this);
-
-	IoEngine::SpawnCoroutine(m_IoStrand, [this, keepAlive](asio::yield_context yc) {
-		if (!m_ShuttingDown) {
-			m_ShuttingDown = true;
+	if (!m_ShuttingDown.exchange(true)) {
+		HttpServerConnection::Ptr keepAlive (this);
 
+		IoEngine::SpawnCoroutine(m_IoStrand, [this, keepAlive](asio::yield_context yc) {
 			Log(LogInformation, "HttpServerConnection")
 				<< "HTTP client disconnected (from " << m_PeerAddress << ")";
 
@@ -104,8 +102,8 @@ void HttpServerConnection::Disconnect()
 			if (listener) {
 				listener->RemoveHttpClient(this);
 			}
-		}
-	});
+		});
+	}
 }
 
 void HttpServerConnection::StartStreaming()
@@ -131,7 +129,7 @@ void HttpServerConnection::StartStreaming()
 	});
 }
 
-bool HttpServerConnection::Disconnected()
+bool HttpServerConnection::Disconnected() const
 {
 	return m_ShuttingDown;
 }
@@ -142,15 +140,11 @@ bool EnsureValidHeaders(
 	boost::beast::flat_buffer& buf,
 	boost::beast::http::parser<true, boost::beast::http::string_body>& parser,
 	boost::beast::http::response<boost::beast::http::string_body>& response,
-	bool& shuttingDown,
 	boost::asio::yield_context& yc
 )
 {
 	namespace http = boost::beast::http;
 
-	if (shuttingDown)
-		return false;
-
 	bool httpError = false;
 	String errorMsg;
 
@@ -337,7 +331,6 @@ bool EnsureValidBody(
 	boost::beast::http::parser<true, boost::beast::http::string_body>& parser,
 	ApiUser::Ptr& authenticatedUser,
 	boost::beast::http::response<boost::beast::http::string_body>& response,
-	bool& shuttingDown,
 	boost::asio::yield_context& yc
 )
 {
@@ -378,9 +371,6 @@ bool EnsureValidBody(
 		parser.body_limit(maxSize);
 	}
 
-	if (shuttingDown)
-		return false;
-
 	boost::system::error_code ec;
 
 	http::async_read(stream, buf, parser, yc[ec]);
@@ -493,7 +483,7 @@ void HttpServerConnection::ProcessMessages(boost::asio::yield_context yc)
 
 			response.set(http::field::server, l_ServerHeader);
 
-			if (!EnsureValidHeaders(*m_Stream, buf, parser, response, m_ShuttingDown, yc)) {
+			if (m_ShuttingDown || !EnsureValidHeaders(*m_Stream, buf, parser, response, yc)) {
 				break;
 			}
 
@@ -542,7 +532,7 @@ void HttpServerConnection::ProcessMessages(boost::asio::yield_context yc)
 				break;
 			}
 
-			if (!EnsureValidBody(*m_Stream, buf, parser, authenticatedUser, response, m_ShuttingDown, yc)) {
+			if (m_ShuttingDown || !EnsureValidBody(*m_Stream, buf, parser, authenticatedUser, response, yc)) {
 				break;
 			}
 

lib/remote/httpserverconnection.hpp

@@ -31,15 +31,15 @@ class HttpServerConnection final : public Object
 	void Disconnect();
 	void StartStreaming();
 
-	bool Disconnected();
+	bool Disconnected() const;
 
 private:
 	ApiUser::Ptr m_ApiUser;
 	Shared<AsioTlsStream>::Ptr m_Stream;
 	double m_Seen;
 	String m_PeerAddress;
 	boost::asio::io_context::strand m_IoStrand;
-	bool m_ShuttingDown;
+	std::atomic<bool> m_ShuttingDown;
 	bool m_HasStartedStreaming;
 	boost::asio::deadline_timer m_CheckLivenessTimer;