Fix bug #2096

ProxySQL was incorrectly not sending COM_PING when multiplexing is disabled

include/MySQL_Data_Stream.h

@@ -203,13 +203,7 @@ class MySQL_Data_Stream
 
 	void return_MySQL_Connection_To_Pool();
 	
-	void destroy_MySQL_Connection_From_Pool(bool sq) {
-		MySQL_Connection *mc=myconn;
-		detach_connection();
-		unplug_backend();
-		mc->send_quit=sq;
-		MyHGM->destroy_MyConn_from_pool(mc);
-	}
+	void destroy_MySQL_Connection_From_Pool(bool sq);
 	void free_mysql_real_query();	
 	void reinit_queues();
 	void destroy_queues();

lib/MySQL_Session.cpp

@@ -1374,7 +1374,9 @@ int MySQL_Session::handler_again___status_PINGING_SERVER() {
 	if (rc==0) {
 		myconn->async_state_machine=ASYNC_IDLE;
 		myconn->compute_unknown_transaction_status();
-		if (mysql_thread___multiplexing && (myconn->reusable==true) && myds->myconn->IsActiveTransaction()==false && myds->myconn->MultiplexDisabled()==false) {
+		//if (mysql_thread___multiplexing && (myconn->reusable==true) && myds->myconn->IsActiveTransaction()==false && myds->myconn->MultiplexDisabled()==false) {
+		// due to issue #2096 we disable the global check on mysql_thread___multiplexing
+		if ((myconn->reusable==true) && myds->myconn->IsActiveTransaction()==false && myds->myconn->MultiplexDisabled()==false) {
 			myds->return_MySQL_Connection_To_Pool();
 		} else {
 			myds->destroy_MySQL_Connection_From_Pool(true);

lib/mysql_data_stream.cpp

@@ -1382,3 +1382,12 @@ void MySQL_Data_Stream::destroy_queues() {
 	queue_destroy(queueIN);
 	queue_destroy(queueOUT);
 }
+
+void MySQL_Data_Stream::destroy_MySQL_Connection_From_Pool(bool sq) {
+	MySQL_Connection *mc=myconn;
+	mc->last_time_used=sess->thread->curtime;
+	detach_connection();
+	unplug_backend();
+	mc->send_quit=sq;
+	MyHGM->destroy_MyConn_from_pool(mc);
+}