The Ultimate Guide to High Availability with MariaDB
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error : (408595) Lost connection to the master server

i find many error in the log file.

-------------------------------

2019-06-24 19:13:25   notice : Initialise the MariaDB Monitor module.
2019-06-24 19:13:25   notice : Loaded module mariadbmon: V1.5.0 from /usr/lib64/maxscale/libmariadbmon.so
2019-06-24 19:13:25   warning: The parameter 'passwd' is deprecated: use 'password' instead
2019-06-24 19:13:25   warning: Protocol module 'mysqlbackend' has been deprecated, use 'mariadbbackend' instead.
2019-06-24 19:13:25   notice : Loaded module mariadbbackend: V2.0.0 from /usr/lib64/maxscale/libmariadbbackend.so
2019-06-24 19:13:25   notice : Loaded module MySQLBackendAuth: V1.0.0 from /usr/lib64/maxscale/libmysqlbackendauth.so
2019-06-24 19:13:25   notice : Loaded module MySQLAuth: V1.1.0 from /usr/lib64/maxscale/libmysqlauth.so
2019-06-24 19:13:25   notice : Loaded module MaxAdminAuth: V2.1.0 from /usr/lib64/maxscale/libmaxadminauth.so
2019-06-24 19:13:25   notice : Housekeeper thread started.
2019-06-24 19:13:25   notice : Encrypted password file /var/lib/maxscale/.secrets can't be accessed (No such file or directory). Password encryption is not used.
2019-06-24 19:13:25   error  : Unknown journal schema version: 1
2019-06-24 19:13:25   notice : Starting a total of 2 services...
2019-06-24 19:13:25   notice : Selecting new master server.
2019-06-24 19:13:25   notice : Setting 'server1' as master.
2019-06-24 19:13:25   notice : Server changed state: server1[172.31.8.18:3306]: new_master. [Running] -> [Master, Running]
2019-06-24 19:13:25   notice : Server changed state: server2[172.31.8.19:3306]: new_slave. [Running] -> [Relay Master, Slave, Running]
2019-06-24 19:13:25   notice : [Read-Write-Service] Loaded 7 MySQL users for listener Read-Write-Listener.
2019-06-24 19:13:25   notice : Listening for connections at [0.0.0.0]:3306 with protocol MySQL
2019-06-24 19:13:25   notice : Service 'Read-Write-Service' started (1/2)
2019-06-24 19:13:25   notice : Listening for connections at [/var/run/maxscale/maxadmin.sock]:0 with protocol MaxScale Admin
2019-06-24 19:13:25   notice : Service 'MaxAdmin-Service' started (2/2)
2019-06-24 19:13:25   notice : Started REST API on [127.0.0.1]:8989
2019-06-24 19:13:25   notice : MaxScale started with 8 worker threads, each with a stack size of 8388608 bytes.
2019-06-24 19:20:24   error  : (751) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (759) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (756) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (761) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (768) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (762) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (774) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.
2019-06-24 19:20:24   error  : (775) Lost connection to the master server, closing session. Lost connection to master server while connection was idle. Connection has 
been idle for 299.6 seconds. Error caused by: #HY000: Lost connection to backend server.

-----------------------------

this is the maxscale.cnf

[root@bogon ]# cat /etc/maxscale.cnf

# MaxScale documentation on GitHub:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Documentation-Contents.md

# Global parameters
#
# Complete list of configuration options:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Getting-Started/Configuration-Guide.md

[maxscale]
threads=auto
# Server definitions
#
# Set the address of the server to the network
# address of a MySQL server.
#

[server1]
type=server
address=172.31.8.18
port=3306
protocol=MySQLBackend
serv_weight=1
# Monitor for the servers
#
# This will keep MaxScale aware of the state of the servers.
# MySQL Monitor documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Monitors/MySQL-Monitor.md
[server2]
type=server
address=172.31.8.19
port=3306
protocol=MySQLBackend
serv_weight=1



[MySQL Monitor]
type=monitor
module=mysqlmon
servers=server1,server2
user=admin
passwd=JD_810927a
monitor_interval=1000
detect_stale_master=true
# Service definitions
#
# Service Definition for a read-only service and
# a read/write splitting service.
#

# ReadConnRoute documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Routers/ReadConnRoute.md

#[Read-Only Service]
#type=service
#router=readconnroute
#servers=server1,server2
#user=admin
#passwd=E2A448DC3A6AD526D172818A8237ADB2
#router_options=slave

# ReadWriteSplit documentation:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Routers/ReadWriteSplit.md

[Read-Write Service]
type=service
router=readwritesplit
servers=server1,server2
user=admin
#router_options=master_accept_reads=false,master_failure_mode=fail_on_write
passwd=JD_810927a
max_slave_connections=60%
use_sql_variables_in=all
auth_all_servers=true



# This service enables the use of the MaxAdmin interface
# MaxScale administration guide:
# https://github.com/mariadb-corporation/MaxScale/blob/2.1/Documentation/Reference/MaxAdmin.md

[MaxAdmin Service]
type=service
router=cli

# Listener definitions for the services
#
# These listeners represent the ports the
# services will listen on.
#

#[Read-Only Listener]
#type=listener
#service=Read-Only Service
#protocol=MySQLClient
#port=4008

[Read-Write Listener]
type=listener
service=Read-Write Service
protocol=MySQLClient
port=3306
address=0.0.0.0


[MaxAdmin Listener]
type=listener
service=MaxAdmin Service
protocol=maxscaled
socket=default
#port=6603

Answer Answered by Markus Mäkelä in this comment.

Try increasing it to a higher value:

SET GLOBAL wait_timeout=3600;

That should allow MaxScale enough time to keep the connection alive with the default connection_keepalive of 300 seconds.

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