Added function close_mysql()

close_mysql() is a replacement for mysql_close()
It tries to avoid blocking while sending the QUIT command

include/mysql_connection.h

@@ -132,5 +132,6 @@ class MySQL_Connection {
 	bool MultiplexDisabled();
 	void ProcessQueryAndSetStatusFlags(char *query_digest_text);
 	void optimize();
+	void close_mysql();
 };
 #endif /* __CLASS_MYSQL_CONNECTION_H */

lib/MySQL_Session.cpp

@@ -57,6 +57,7 @@ static void * kill_query_thread(void *arg) {
 	}
 	char buf[100];
 	sprintf(buf,"KILL QUERY %lu", ka->id);
+	// FIXME: these 2 calls are blocking, fortunately on their own thread
 	mysql_query(mysql,buf);
 	mysql_close(mysql);
 __exit_kill_query_thread:

lib/mysql_connection.cpp

@@ -173,12 +173,7 @@ MySQL_Connection::~MySQL_Connection() {
 		// always decrease the counter
 		__sync_fetch_and_sub(&MyHGM->status.server_connections_connected,1);
 		async_free_result();
-		if (send_quit) {
-			mysql_close(mysql);
-		} else {
-			mysql_close_no_command(mysql);
-			shutdown(fd, SHUT_RDWR);
-		}
+		close_mysql(); // this take care of closing mysql connection
 		mysql=NULL;
 	}
 //	// FIXME: with the use of mysql client library , this part should be gone.
@@ -1096,3 +1091,21 @@ void MySQL_Connection::optimize() {
 		}
 	}
 }
+
+// close_mysql() is a replacement for mysql_close()
+// if avoids that a QUIT command stops forever
+// FIXME: currently doesn't support encryption and compression
+void MySQL_Connection::close_mysql() {
+	if (send_quit) {
+		char buff[5];
+		mysql_hdr myhdr;
+		myhdr.pkt_id=0;
+		myhdr.pkt_length=1;
+		memcpy(buff, &myhdr, sizeof(mysql_hdr));
+		buff[4]=0x01;
+		int fd=mysql->net.fd;
+		send(fd, buff, 5, MSG_NOSIGNAL);
+	}
+	mysql_close_no_command(mysql);
+	shutdown(fd, SHUT_RDWR);
+}