MariaDB 10.4.8
Maxscale 2.4.2

git clone https://github.com/mariadb-corporation/maxscale-docker.git
cd maxscale-docker
cd maxscale

ログを標準出力からファイルに変更する場合

maxscale.cnfを追加

maxscale.cnf

[maxscale]
threads=auto
admin_host=0.0.0.0
logdir=/var/log/maxscale

[server1]
type=server
address=master
port=3306
protocol=mariadbbackend

[server2]
type=server
address=slave1
port=3306
protocol=mariadbbackend

[server3]
type=server
address=slave2
port=3306
protocol=mariadbbackend

[MariaDB-Monitor]
type=monitor
module=mariadbmon
servers=server1,server2,server3
user=maxuser
password=maxpwd
auto_failover=true
auto_rejoin=true
enforce_read_only_slaves=1

[Read-Only-Service]
type=service
router=readconnroute
servers=server1,server2,server3
user=maxuser
password=maxpwd
router_options=slave

[Read-Write-Service]
type=service
router=readwritesplit
servers=server1,server2,server3
user=maxuser
password=maxpwd
master_failure_mode=fail_on_write

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

[Read-Write-Listener]
type=listener
service=Read-Write-Service
protocol=mariadbclient
port=4006

docker-compose.yml編集
・mariadb:10.3 → 10.4.8
・mariadb/maxscale:latest → maxscale:2.4.2
・maxscaleに「command: ["maxscale", "-d", "-U", "maxscale", "-l", "file"]」を追加

docker-compose.yml

version: '2'
services:
    master:
        image: mariadb:10.4.8
        environment:
            MYSQL_ALLOW_EMPTY_PASSWORD: 'Y'
        volumes:
            - ./sql/master:/docker-entrypoint-initdb.d
        command: mysqld --log-bin=mariadb-bin --binlog-format=ROW --server-id=3000
        ports:
            - "4001:3306"

    slave1:
        image: mariadb:10.4.8
        depends_on:
            - master
        environment:
            MYSQL_ALLOW_EMPTY_PASSWORD: 'Y'
        volumes:
            - ./sql/slave:/docker-entrypoint-initdb.d
        command: mysqld --log-bin=mariadb-bin --binlog-format=ROW --server-id=3001 --log-slave-updates
        ports:
            - "4002:3306"

    slave2:
        image: mariadb:10.4.8
        depends_on:
            - master
        environment:
            MYSQL_ALLOW_EMPTY_PASSWORD: 'Y'
        volumes:
            - ./sql/slave:/docker-entrypoint-initdb.d
        command: mysqld --log-bin=mariadb-bin --binlog-format=ROW --server-id=3002 --log-slave-updates
        ports:
            - "4003:3306"

    maxscale:
        image: mariadb/maxscale:2.4.2-0
        depends_on:
            - master
            - slave1
            - slave2
        volumes:
            - ./maxscale.cnf:/etc/maxscale.cnf
        command: ["maxscale", "-d", "-U", "maxscale", "-l", "file"]
        ports:
            - "4006:4006"  # readwrite port
            - "4008:4008"  # readonly port
            - "8989:8989"  # REST API port

docker-compose up -d
docker-compose exec maxscale maxctrl list servers

┌─────────┬─────────┬──────┬─────────────┬─────────────────┬──────────┐
│ Server  │ Address │ Port │ Connections │ State           │ GTID     │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server1 │ master  │ 3306 │ 0           │ Master, Running │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server2 │ slave1  │ 3306 │ 0           │ Slave, Running  │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server3 │ slave2  │ 3306 │ 0           │ Slave, Running  │ 0-3000-5 │
└─────────┴─────────┴──────┴─────────────┴─────────────────┴──────────┘

docker stop maxscale_master_1
docker-compose exec maxscale maxctrl list servers

┌─────────┬─────────┬──────┬─────────────┬─────────────────┬──────────┐
│ Server  │ Address │ Port │ Connections │ State           │ GTID     │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server1 │ master  │ 3306 │ 0           │ Down            │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server2 │ slave1  │ 3306 │ 0           │ Master, Running │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server3 │ slave2  │ 3306 │ 0           │ Slave, Running  │ 0-3000-5 │
└─────────┴─────────┴──────┴─────────────┴─────────────────┴──────────┘

docker start maxscale_master_1
docker-compose exec maxscale maxctrl list servers

┌─────────┬─────────┬──────┬─────────────┬─────────────────┬──────────┐
│ Server  │ Address │ Port │ Connections │ State           │ GTID     │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server1 │ master  │ 3306 │ 0           │ Slave, Running  │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server2 │ slave1  │ 3306 │ 0           │ Master, Running │ 0-3000-5 │
├─────────┼─────────┼──────┼─────────────┼─────────────────┼──────────┤
│ server3 │ slave2  │ 3306 │ 0           │ Slave, Running  │ 0-3000-5 │
└─────────┴─────────┴──────┴─────────────┴─────────────────┴──────────┘

docker exec -t maxscale_maxscale_1 bash
ls /var/log/maxscale

maxscale.log

cat /var/log/maxscale/maxscale.log

# ログの出力例
2019-09-04 17:43:23   notice : Starting a total of 2 services...
2019-09-04 17:43:23   error  : [Read-Write-Service] Failed to connect to server 'server1' ([master]:3306) when checking authentication user credentials and permissions: 2002 Can't connect to MySQL server on 'master' (115)
2019-09-04 17:43:23   error  : [Read-Write-Service] Failed to connect to server 'server2' ([slave1]:3306) when checking authentication user credentials and permissions: 2002 Can't connect to MySQL server on 'slave1' (115)
2019-09-04 17:43:23   error  : Monitor was unable to connect to server server1[master:3306] : 'Can't connect to MySQL server on 'master' (115)'
2019-09-04 17:43:23   error  : [Read-Write-Service] Failed to connect to server 'server3' ([slave2]:3306) when checking authentication user credentials and permissions: 2002 Can't connect to MySQL server on 'slave2' (115)
2019-09-04 17:43:23   error  : Failure loading users data from backend [master:3306] for service [Read-Write-Service]. MySQL error 2002, Can't connect to MySQL server on 'master' (115)