Client: receive and parse greeting asynchronously

Before this patch the greetings was received in blocking mode
right after blocking connect.

This patch postpones greetings to the first reading.

Part of #28

Author: alyapunov

src/Client/Connection.hpp

@@ -84,6 +84,7 @@ struct ConnectionImpl
 	//Members below can be default-initialized.
 	ConnectionError error;
 	Greeting greeting;
+	bool is_greeting_received;
 	std::unordered_map<rid_t, Response<BUFFER>> futures;
 
 	static constexpr size_t AVAILABLE_IOVEC_COUNT = 32;
@@ -568,13 +569,14 @@ int
 decodeGreeting(Connection<BUFFER, NetProvider> &conn)
 {
 	//TODO: that's not zero-copy, should be rewritten in that pattern.
+	assert(conn.getInBuf().has(conn.impl->endDecoded, Iproto::GREETING_SIZE));
 	char greeting_buf[Iproto::GREETING_SIZE];
 	conn.impl->endDecoded.read({greeting_buf, sizeof(greeting_buf)});
-	assert(conn.impl->endDecoded == conn.impl->inBuf.end());
 	conn.impl->dec.reset(conn.impl->endDecoded);
 	if (parseGreeting(std::string_view{greeting_buf, Iproto::GREETING_SIZE},
 			  conn.impl->greeting) != 0)
 		return -1;
+	conn.impl->is_greeting_received = true;
 	LOG_DEBUG("Version: ", conn.impl->greeting.version_id);
 
 #ifndef NDEBUG

src/Client/EpollNetProvider.hpp

@@ -145,27 +145,7 @@ EpollNetProvider<BUFFER, NETWORK>::connect(Conn_t &conn,
 		return -1;
 	}
 	LOG_DEBUG("Connected to ", addr, ", socket is ", socket);
-	/* Receive and decode greetings. */
-	size_t iov_cnt = 0;
-	struct iovec *iov =
-		inBufferToIOV(conn, Iproto::GREETING_SIZE, &iov_cnt);
-	LOG_DEBUG("Receiving greetings...");
-	int read_bytes = NETWORK::recvall(socket, iov, iov_cnt, false);
-	if (read_bytes < 0) {
-		conn.setError(std::string("Failed to receive greetings: ") +
-			      strerror(errno));
-		::close(socket);
-		return -1;
-	}
-	LOG_DEBUG("Greetings are received, read bytes ", read_bytes);
-	if (decodeGreeting(conn) != 0) {
-		conn.setError(std::string("Failed to decode greetings"));
-		::close(socket);
-		return -1;
-	}
-	LOG_DEBUG("Greetings are decoded");
-	LOG_DEBUG("Authentication processing...");
-	//TODO: add authentication step.
+	conn.getImpl()->is_greeting_received = false;
 	conn.setSocket(socket);
 	registerEpoll(conn);
 	return 0;
@@ -232,6 +212,20 @@ EpollNetProvider<BUFFER, NETWORK>::recv(Conn_t &conn)
 					  strerror(errno), errno);
 		return -1;
 	}
+
+	if (!conn.getImpl()->is_greeting_received) {
+		if ((size_t) rcvd < Iproto::GREETING_SIZE)
+			return 0;
+		/* Receive and decode greetings. */
+		LOG_DEBUG("Greetings are received, read bytes ", rcvd);
+		if (decodeGreeting(conn) != 0) {
+			conn.setError("Failed to decode greetings");
+			return -1;
+		}
+		LOG_DEBUG("Greetings are decoded");
+		rcvd -= Iproto::GREETING_SIZE;
+	}
+
 	return 0;
 }
 

src/Client/LibevNetProvider.hpp

@@ -139,6 +139,20 @@ connectionReceive(Connection<BUFFER,  LibevNetProvider<BUFFER, NETWORK>> &conn)
 			       strerror(errno));
 		return -1;
 	}
+
+	if (!conn.getImpl()->is_greeting_received) {
+		if ((size_t) rcvd < Iproto::GREETING_SIZE)
+			return 0;
+		/* Receive and decode greetings. */
+		LOG_DEBUG("Greetings are received, read bytes ", rcvd);
+		if (decodeGreeting(conn) != 0) {
+			conn.setError("Failed to decode greetings");
+			return -1;
+		}
+		LOG_DEBUG("Greetings are decoded");
+		rcvd -= Iproto::GREETING_SIZE;
+	}
+
 	return 0;
 }
 
@@ -289,25 +303,8 @@ LibevNetProvider<BUFFER, NETWORK>::connect(Conn_t &conn,
 		return -1;
 	}
 	LOG_DEBUG("Connected to ", addr, ", socket is ", socket);
-	/* Receive and decode greetings. */
-	size_t iov_cnt = 0;
-	struct iovec *iov = inBufferToIOV(conn, Iproto::GREETING_SIZE, &iov_cnt);
-	LOG_DEBUG("Receiving greetings...");
-	int read_bytes = NETWORK::recvall(socket, iov, iov_cnt, false);
-	if (read_bytes < 0) {
-		conn.setError(std::string("Failed to receive greetings: ") +
-			      strerror(errno));
-		::close(socket);
-		return -1;
-	}
-	LOG_DEBUG("Greetings are received, read bytes ", read_bytes);
-	if (decodeGreeting(conn) != 0) {
-		conn.setError(std::string("Failed to decode greetings"));
-		::close(socket);
-		return -1;
-	}
+	conn.getImpl()->is_greeting_received = false;
 
-	LOG_DEBUG("Greetings are decoded");
 	registerWatchers(conn, socket);
 
 	conn.setSocket(socket);