Merge pull request #3202 from sysown/v2.0.16-3201

Closes #3201: Connections not being cleanup in case of 'match_tracked_options' always failing
sysown · Dec 27, 2020 · d6239aa · d6239aa
2 parents 5124f0e + c88a9a9
commit d6239aa
Showing 1 changed file with 32 additions and 5 deletions.
diff --git a/lib/MySQL_HostGroups_Manager.cpp b/lib/MySQL_HostGroups_Manager.cpp
@@ -2701,11 +2701,38 @@ MySQL_Connection * MySrvConnList::get_random_MyConn(MySQL_Session *sess, bool ff
 			// 2 : tracked options are OK , CHANGE USER is not required, but some SET statement or INIT_DB needs to be executed
 			switch (connection_quality_level) {
 				case 0: // not found any good connection, tracked options are not OK
-					// we must create a new connection
-					conn = new MySQL_Connection();
-					conn->parent=mysrvc;
-					__sync_fetch_and_add(&MyHGM->status.server_connections_created, 1);
-					proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Returning MySQL Connection %p, server %s:%d\n", conn, conn->parent->address, conn->parent->port);
+					// we must check if connections need to be freed before
+					// creating a new connection
+					{
+						unsigned int conns_free = mysrvc->ConnectionsFree->conns_length();
+						unsigned int conns_used = mysrvc->ConnectionsUsed->conns_length();
+						unsigned int pct_max_connections = (3 * mysrvc->max_connections) / 4;
+						unsigned int connections_to_free = 0;
+
+						if (conns_free >= 1) {
+							// connection cleanup is triggered when connectinos exceed 3/4 of the total
+							// allowed max connections, this cleanup ensures that at least *one connection*
+							// will be freed.
+							if (pct_max_connections <= (conns_free + conns_used)) {
+								connections_to_free = (conns_free + conns_used) - pct_max_connections;
+								if (connections_to_free == 0) connections_to_free = 1;
+							}
+
+							while (conns_free && connections_to_free) {
+								MySQL_Connection* conn = mysrvc->ConnectionsFree->remove(0);
+								delete conn;
+
+								conns_free = mysrvc->ConnectionsFree->conns_length();
+								connections_to_free -= 1;
+							}
+						}
+
+						// we must create a new connection
+						conn = new MySQL_Connection();
+						conn->parent=mysrvc;
+						__sync_fetch_and_add(&MyHGM->status.server_connections_created, 1);
+						proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Returning MySQL Connection %p, server %s:%d\n", conn, conn->parent->address, conn->parent->port);
+					}
 					break;
 				case 1: //tracked options are OK , but CHANGE USER is required
 					// we may consider creating a new connection