The Ultimate Guide to High Availability with MariaDB
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MaxScale always checked dbserv node lost ,but I do not know why ?

Sometimes, when I connect to Galera cluster through the maxscale proxy, it appears: FATAL: mysql_drv_query() returned error 2003 (Lost connection to backend server.) ，But the nodes are in normal state. At the same time, I looked at the maxscale running log and found that the nodes were frequently lost.

Here is the log content

2019-05-13 00:43:27   notice : Server changed state: dbserv1[10.231.3.244:3306]: new_slave. [Running] -> [Slave, Synced, Running]
2019-05-13 00:59:37   notice : Server changed state: dbserv3[10.231.5.52:3306]: lost_slave. [Slave, Synced, Running] -> [Running]
2019-05-13 00:59:47   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_slave. [Running] -> [Slave, Synced, Running]
2019-05-13 02:04:25   notice : Server changed state: dbserv3[10.231.5.52:3306]: lost_slave. [Slave, Synced, Running] -> [Running]
2019-05-13 02:04:35   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_slave. [Running] -> [Slave, Synced, Running]
2019-05-13 02:09:55   error  : Failed to create new routing session. Couldn't find eligible candidate server. Freeing allocated resources.
2019-05-13 02:09:55   error  : Failed to create new router session for service 'GaleraServiceWrite'. See previous errors for more details.
2019-05-13 02:09:55   notice : Server changed state: dbserv2[10.231.4.180:3306]: lost_master. [Master, Synced, Running] -> [Running]
2019-05-13 02:09:55   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_master. [Slave, Synced, Running] -> [Master, Synced, Running]
2019-05-13 02:10:05   notice : Server changed state: dbserv2[10.231.4.180:3306]: new_master. [Running] -> [Master, Synced, Running]
2019-05-13 02:10:05   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_slave. [Master, Synced, Running] -> [Slave, Synced, Running]
2019-05-13 02:26:24   notice : Server changed state: dbserv2[10.231.4.180:3306]: lost_master. [Master, Synced, Running] -> [Running]
2019-05-13 02:26:24   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_master. [Slave, Synced, Running] -> [Master, Synced, Running]
2019-05-13 02:26:34   notice : Server changed state: dbserv2[10.231.4.180:3306]: new_master. [Running] -> [Master, Synced, Running]
2019-05-13 02:26:34   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_slave. [Master, Synced, Running] -> [Slave, Synced, Running]
2019-05-13 02:45:23   notice : Server changed state: dbserv1[10.231.3.244:3306]: lost_slave. [Slave, Synced, Running] -> [Running]
2019-05-13 02:45:34   notice : Server changed state: dbserv1[10.231.3.244:3306]: new_slave. [Running] -> [Slave, Synced, Running]
2019-05-13 03:14:11   notice : Server changed state: dbserv1[10.231.3.244:3306]: lost_slave. [Slave, Synced, Running] -> [Running]
2019-05-13 03:14:23   notice : Server changed state: dbserv1[10.231.3.244:3306]: new_slave. [Running] -> [Slave, Synced, Running]
2019-05-13 03:26:08   notice : Server changed state: dbserv1[10.231.3.244:3306]: slave_down. [Slave, Synced, Running] -> [Down]
2019-05-13 03:26:18   notice : Server changed state: dbserv1[10.231.3.244:3306]: slave_up. [Down] -> [Slave, Synced, Running]
2019-05-13 03:32:25   error  : Failed to route MySQL command 3 to backend server.
2019-05-13 03:32:25   error  : Routing the query failed. Session will be closed.
2019-05-13 03:32:25   notice : Server changed state: dbserv2[10.231.4.180:3306]: master_down. [Master, Synced, Running] -> [Down]
2019-05-13 03:32:25   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_master. [Slave, Synced, Running] -> [Master, Synced, Running]
2019-05-13 03:32:37   notice : Server changed state: dbserv2[10.231.4.180:3306]: master_up. [Down] -> [Master, Synced, Running]
2019-05-13 03:32:37   notice : Server changed state: dbserv3[10.231.5.52:3306]: new_slave. [Master, Synced, Running] -> [Slave, Synced, Running]
2019-05-13 03:50:03   notice : Server changed state: dbserv1[10.231.3.244:3306]: lost_slave. [Slave, Synced, Running] -> [Running]
2019-05-13 03:50:14   notice : Server changed state: dbserv1[10.231.3.244:3306]: server_down. [Running] -> [Down]
2019-05-13 03:50:34   error  : Failed to route MySQL command 3 to backend server.
2019-05-13 03:50:34   error  : Routing the query failed. Session will be closed.
2019-05-13 03:50:35   error  : Failed to route MySQL command 3 to backend server.
2019-05-13 03:50:35   error  : Routing the query failed. Session will be closed.

Answer Answered by Markus Mäkelä in this comment.

Can you try and see if using the latest 2.3 version fixes it?

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