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ProxySQL 3.0.1-debian’s Group Replication monitor errors out against MySQL 9.1.0 because it expects a 4-column result but gets only 3:
2025-05-19 14:21:33 MySQL_Monitor.cpp:4105:gr_report_fetching_errs(): [ERROR] Got error. mmsd 0x7d8069638000 , MYSQL 0x7d8066604600 , FD 54 : Invalid or malformed resultset
2025-05-19 14:21:33 MySQL_Monitor.cpp:3855:extract_gr_srv_st(): [ERROR] Invalid resultset for GR monitoring query from server mysql9-1.mysql9-pods.demo.svc:3306. Either 'mysql_fetch_fields=NULL' or unexpected 'mysql_num_fields=3'. Please report this incident
All replicas are marked ONLINE in runtime_mysql_servers, and regular queries routed through ProxySQL succeed.
ProxySQLAdmin> select * from mysql_group_replication_hostgroups;
+------------------+-------------------------+------------------+-------------------+--------+-------------+-----------------------+-------------------------+---------+
| writer_hostgroup | backup_writer_hostgroup | reader_hostgroup | offline_hostgroup | active | max_writers | writer_is_also_reader | max_transactions_behind | comment |
+------------------+-------------------------+------------------+-------------------+--------+-------------+-----------------------+-------------------------+---------+
| 2 | 4 | 3 | 1 | 1 | 1 | 1 | 0 | |
+------------------+-------------------------+------------------+-------------------+--------+-------------+-----------------------+-------------------------+---------+
1 row in set (0.000 sec)
ProxySQLAdmin> select * from runtime_mysql_servers;
+--------------+-------------------------------+------+-----------+--------+--------+-------------+-----------------+---------------------+---------+----------------+---------+
| hostgroup_id | hostname | port | gtid_port | status | weight | compression | max_connections | max_replication_lag | use_ssl | max_latency_ms | comment |
+--------------+-------------------------------+------+-----------+--------+--------+-------------+-----------------+---------------------+---------+----------------+---------+
| 2 | mysql9-0.mysql9-pods.demo.svc | 3306 | 0 | ONLINE | 1 | 0 | 1000 | 0 | 0 | 0 | |
| 3 | mysql9-0.mysql9-pods.demo.svc | 3306 | 0 | ONLINE | 1 | 0 | 1000 | 0 | 0 | 0 | |
| 3 | mysql9-1.mysql9-pods.demo.svc | 3306 | 0 | ONLINE | 1 | 0 | 1000 | 0 | 0 | 0 | |
| 3 | mysql9-2.mysql9-pods.demo.svc | 3306 | 0 | ONLINE | 1 | 0 | 1000 | 0 | 0 | 0 | |
+--------------+-------------------------------+------+-----------+--------+--------+-------------+-----------------+---------------------+---------+----------------+---------+
4 rows in set (0.001 sec)
ProxySQLAdmin> SELECT * FROM stats.stats_mysql_connection_pool;
+-----------+-------------------------------+----------+--------+----------+----------+--------+---------+-------------+---------+-------------------+-----------------+-----------------+------------+
| hostgroup | srv_host | srv_port | status | ConnUsed | ConnFree | ConnOK | ConnERR | MaxConnUsed | Queries | Queries_GTID_sync | Bytes_data_sent | Bytes_data_recv | Latency_us |
+-----------+-------------------------------+----------+--------+----------+----------+--------+---------+-------------+---------+-------------------+-----------------+-----------------+------------+
| 2 | mysql9-0.mysql9-pods.demo.svc | 3306 | ONLINE | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 57 |
| 3 | mysql9-0.mysql9-pods.demo.svc | 3306 | ONLINE | 0 | 1 | 1 | 0 | 1 | 983 | 0 | 19660 | 29490 | 57 |
| 3 | mysql9-1.mysql9-pods.demo.svc | 3306 | ONLINE | 0 | 1 | 1 | 0 | 1 | 1020 | 0 | 20400 | 30600 | 55 |
| 3 | mysql9-2.mysql9-pods.demo.svc | 3306 | ONLINE | 0 | 1 | 1 | 0 | 1 | 997 | 0 | 19940 | 29910 | 63 |
+-----------+-------------------------------+----------+--------+----------+----------+--------+---------+-------------+---------+-------------------+-----------------+-----------------+------------+
4 rows in set (0.000 sec)
Environment:
ProxySQL: 3.0.1-debian
Backends: MySQL 9.1.0 (Group Replication), MySQL 8.4.3 works without errors
Stats show queries are being executed.
Reproduction:
Configure a GR hostgroup for MySQL 9.1.0 replicas.
Run ProxySQL.
Observe log errors
Monitor logs “mysql_num_fields=3” and flags malformed resultset, despite traffic still flowing correctly.
If MySQL 9 is supported, how should I fix this?
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