L'environnement d'exploitation de ce tutoriel : système windows7, version mysql8, ordinateur Dell G3.
MySQL Router est un middleware léger officiellement fourni par MySQL et fait partie du cluster InnoDB, qui assure la transparence entre les applications et les serveurs MySQL back-end. Il est principalement utilisé pour résoudre les problèmes de haute disponibilité, d'équilibrage de charge et d'expansion facile du cluster de bases de données maître-esclave MySQL. Le routeur sert de couche de transfert de trafic, située entre l'application et le serveur MySQL, et sa fonction est similaire à celle de LVS.
Basé sur le mécanisme de réplication de groupe (MGR), lorsque le nœud maître tombe en panne et quitte le cluster, les nœuds restants éliront un nouveau nœud maître basé sur le protocole paxos. Il y a un problème ici. Si l'application est connectée au nœud maître et que le nœud maître plante et quitte le cluster, l'adresse IP de la base de données disponible change. À ce moment, l'application client essaiera toujours de se connecter au nœud défaillant. bien que le client puisse être modifié. Configuration de connexion de l'application finale, mais cette situation est fondamentalement irréaliste.
La combinaison de la réplication de groupe MySQL et de MySQL Shel est la suivante :
La figure ci-dessus illustre pleinement le rôle du routeur MySQL dans le cluster InnoDB. Sa fonction principale est de. fournir un cluster de base de données L'adresse IP virtuelle sert de point de connexion unique pour les applications. Grâce à ce point de connexion unique, des solutions de haute disponibilité de base de données telles que l'équilibrage de charge, la séparation en lecture-écriture et le basculement peuvent être mises en œuvre.
Il est recommandé d'installer MySQL Router sur la machine sur laquelle se trouve l'application, pour les raisons suivantes :
Le processus de démarrage est lent et les informations de démarrage sont visibles dans le journal
Le routeur MySQL recherchera par défaut "mysqlrouter.conf" dans le répertoire d'installation et ".mysqlrouter.conf" dans le répertoire personnel. Vous pouvez également utiliser "-c" ou "--config" sous la commande mysqlrouter du programme binaire pour spécifier manuellement le fichier de configuration.
mode : propose deux modes, lecture seule et lecture-écriture, ainsi que le mode de planification de lecture-écriture est la première disponible. La méthode de planification en lecture seule est le round-robin
routing_strategy : stratégie de routage, y compris les stratégies de round-robin et de première disponibilité
[root@node4 etc]# mysqlrouter --config /usr/local/mysqlrouter/etc/mysqlrouter.conf &
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3.2.7 Vérifiez si L'écoute du port du routeur MySQL est activée
[root@node4 etc]# netstat -ntlp |grep mysqlrouter
tcp 0 0 172.16.8.68:7001 0.0.0.0:* LISTEN 9221/mysqlrouter
tcp 0 0 172.16.8.68:7002 0.0.0.0:* LISTEN 9221/mysqlrouter
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Test fonctionnel
Ce qui suit. les tests sont tous sous InnoDB Cluster. Le mode d'installation du routeur MySQL est bootstrap.4.1路由验证
4.1.1测试通过MySQL Router连接6446 RW端口，查看连接的是否为primary
[root@node4 mysqlrouter]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6446 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
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测试结果： 使用6446 RW端口会访问到后端InnoDB Cluster的primary
4.1.2测试通过MySQL Router连接6447 RO端口，查看连接的是否为seconde节点，rr算法是否生效
[root@node4 mysqlrouter]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6447 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
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测试结果： 使用6447 RO端口会连接到后端InnoDB Cluster集群中所有的seconde节点，并且以rr(round-robin)的策略调度
4.2高可用测试
4.2.1模拟其中一台seconde节点宕机，查看MySQL Router是否会自动取消该节点的路由
(1) 停掉一台seconde节点
[root@oratest52 ~]# systemctl status mysql
[root@oratest52 ~]# systemctl stop mysql
[root@oratest52 ~]# systemctl status mysql
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(2) 在InnoDB Cluster中查看集群状态，可以看到oratest52已经处于MISSING状态
MySQL 172.16.9.51:3306 JS > cluster.status()
{
"clusterName": "st",
"defaultReplicaSet": {
"name": "default",
"primary": "oratest51:3306",
"ssl": "DISABLED",
"status": "OK_NO_TOLERANCE",
"statusText": "Cluster is NOT tolerant to any failures. 1 member is not active",
"topology": {
"oratest51:3306": {
"address": "oratest61:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"oratest52:3306": {
"address": "oratest52:3306",
"mode": "n/a",
"readReplicas": {},
"role": "HA",
"shellConnectError": "MySQL Error 2003 (HY000): Can't connect to MySQL server on 'oratest52' (111)",
"status": "(MISSING)"
},
"test61:3306": {
"address": "test51:3306",
"mode": "R/W",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
}
},
"topologyMode": "Single-Primary"
},
"groupInformationSourceMember": "test61:3306"
}Copier après la connexion
(3) 在MGR中查看GR状态，可以看到已经没有oratest52这台机器
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 48cdca42-a386-11e9-95f1-0050569d2587 | test61 | 3306 | ONLINE |
| group_replication_applier | e9ee5267-a386-11e9-ac35-0050569d9ef5 | oratest51 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
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(4) 测试通过6447 RO端口连接，查看是否会自动剔除宕机的oratest52节点
[root@node4 ~]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6447 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
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测试结果： MySQL Router会自动剔除宕机的oratest52节点，read请求只会转发到后端正常的MySQL实例，过程无需人工干预。
4.2.2启动上一步中停止的MySQL实例，确认MGR和InnoDB Cluster一切正常后，查看MySQL Router是否会自动加入这台已恢复的实例进行转发
(1) 启动oratest52的MySQL服务
[root@oratest52 ~]# systemctl start mysql
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(2)启动MGR，并确认MGR状态正常
mysql> start group_replication;
Query OK, 0 rows affected (2.92 sec)
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 48cdca42-a386-11e9-95f1-0050569d2587 | test61 | 3306 | ONLINE |
| group_replication_applier | 50bc1160-a386-11e9-92c9-0050569dc0da | oratest52 | 3306 | ONLINE |
| group_replication_applier | e9ee5267-a386-11e9-ac35-0050569d9ef5 | oratest51 | 3306 | ONLINE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
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(3) 检查InnoDB Cluster是否正常
MySQL 172.16.9.51:3306 JS > cluster.status()
{
"clusterName": "st",
"defaultReplicaSet": {
"name": "default",
"primary": "oratest51:3306",
"ssl": "DISABLED",
"status": "OK",
"statusText": "Cluster is ONLINE and can tolerate up to ONE failure.",
"topology": {
"oratest51:3306": {
"address": "oratest61:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"oratest52:3306": {
"address": "oratest52:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"test61:3306": {
"address": "test51:3306",
"mode": "R/W",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
}
},
"topologyMode": "Single-Primary"
},
"groupInformationSourceMember": "test61:3306"
}Copier après la connexion
(4) 查看恢复正常的实例，能不能自动加入MySQL Router进行转发，可以看到oratest52可以被正常调度
[root@node4 mysqlrouter]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6447 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
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测试结果： 恢复正常的MySQL实例可以自动加入MySQL Router并进行转发，无需人工干预。
4.2.3模拟停掉primary节点，测试MySQL Router如何处理发送RW端口的请求，MySQL Router怎样获取新的primary节点
(1) 当前primary节点是oratest51，在primary节点上停止MySQL，确认停止成功
[root@oratest51 data]# systemctl status mysql
[root@oratest51 data]# systemctl stop mysql
[root@oratest51 data]# systemctl status mysql
[root@oratest51 data]# ps -ef |grep mysql
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(2) 查看InnoDB Cluster状态，可以看到oratest51已经处于MISSING状态，primary节点已经切换到了test61
MySQL 172.16.9.61:3306 JS > cluster.status();
{
"clusterName": "st",
"defaultReplicaSet": {
"name": "default",
"primary": "test61:3306",
"ssl": "DISABLED",
"status": "OK_NO_TOLERANCE",
"statusText": "Cluster is NOT tolerant to any failures. 1 member is not active",
"topology": {
"oratest51:3306": {
"address": "oratest51:3306",
"mode": "n/a",
"readReplicas": {},
"role": "HA",
"shellConnectError": "MySQL Error 2003 (HY000): Can't connect to MySQL server on 'oratest51' (111)",
"status": "(MISSING)"
},
"oratest52:3306": {
"address": "oratest52:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"test61:3306": {
"address": "test61:3306",
"mode": "R/W",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
}
},
"topologyMode": "Single-Primary"
},
"groupInformationSourceMember": "test61:3306"
}Copier après la connexion
(3) 测试连接到RW 6446端口，查看是否可以正常连接到新的primary节点test61，并且写入数据否正常
[root@node2 mysqlrouter]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6446 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
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测试结果： 当primary节点挂掉之后，MySQL Router会自动去连接新的primary节点
4.2.4启动上一步中停掉的oratest51，将状态恢复正常，测试MySQL Router能不能自动加入这台已恢复的节点并调度
(1) 启动oratest51，将状态恢复正常
[root@oratest51 ~]# systemctl start mysql
[root@oratest51 ~]# systemctl status mysql
[root@oratest51 ~]# mysql -uroot -p123456
mysql> start group_replication;
mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID |MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+------------+-------------+--------------+
| group_replication_applier | 48cdca42-a386-11e9-95f1-0050569d2587 |test61 | 3306 | ONLINE |
| group_replication_applier | 50bc1160-a386-11e9-92c9-0050569dc0da |oratest52 | 3306 | ONLINE |
| group_replication_applier | e9ee5267-a386-11e9-ac35-0050569d9ef5 |oratest51 | 3306 | ONLINE |
+---------------------------+--------------------------------------+------------+-------------+--------------+
3 rows in set (0.00 sec)
mysql> quit
[root@oratest51 local]# mysqlsh
MySQL JS > shell.connect('root@172.16.9.51:3306')
MySQL 172.16.9.51:3306 JS > var cluster = dba.getCluster()
MySQL 172.16.9.51:3306 JS > cluster.status();
{
"clusterName": "st",
"defaultReplicaSet": {
"name": "default",
"primary": "test61:3306",
"ssl": "DISABLED",
"status": "OK",
"statusText": "Cluster is ONLINE and can tolerate up to ONE failure.",
"topology": {
"oratest51:3306": {
"address": "oratest51:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"oratest52:3306": {
"address": "oratest52:3306",
"mode": "R/O",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
},
"test61:3306": {
"address": "test61:3306",
"mode": "R/W",
"readReplicas": {},
"role": "HA",
"status": "ONLINE"
}
},
"topologyMode": "Single-Primary"
},
"groupInformationSourceMember": "test61:3306"
}Copier après la connexion
(2) 测试RO端口的Router调度
[root@node4 mysqlrouter]# for ((i=0;i<=5;i++));do mysql -h172.16.8.101 -uroot -p123456 -P6447 -e"select @@hostname;";done;
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest51 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| oratest52 |
+------------+
mysql: [Warning] Using a password on the command line interface can be insecure.
+------------+
| @@hostname |
+------------+
| test61 |
+------------+
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测试结果： 恢复正常的实例加入集群后，会自动加入到MySQL Router并进行调度
五、运维相关
5.1数据库节点变更
MySQL Router在初始化配置的时候是连接到集群节点读取集群的元数据的。如果在集群中新增或减少节点，需要同步更新MySQL Router的配置，否则无法生效
# mysqlrouter --bootstrap 172.16.9.51:3306 --directory /data/mysqlrouter --user=root --conf-use-sockets --force
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更新了MySQL Router的配置的配置，需要重启MySQL Router：
#systemctl restart mysqlrouter
#systemctl status mysqlrouter
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六、问题汇总
6.1初始化MySQL Router前，需要停止group_replication
报错如下
[root@oratest51 data]# mysqlrouter --bootstrap root@172.16.9.51:3310 --directory /data/mysqlrouter --conf-use-sockets --user=root
Please enter MySQL password for root:
Error: Unable to connect to the metadata server: Error connecting to MySQL server at 172.16.9.51:3310: Can't connect to MySQL server on '172.16.9.51' (111) (2003)
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原因： 需要配置连接用户的权限
解决办法： 给连接用户配置所有权限，如下：
mysql> grant all privileges on *.* to root@'%' identified by "123456";
mysql> flush privileges;
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[root@oratest51 data]# mysqlrouter --bootstrap root@172.16.9.51:3306 --directory /data/mysqlrouter --conf-use-sockets --user=root
Please enter MySQL password for root:
Error: Expected MySQL Server '172.16.9.51:3306' to contain the metadata of MySQL InnoDB Cluster, but the schema does not exist.
Checking version of the metadata schema failed with: Error executing MySQL query: Table 'mysql_innodb_cluster_metadata.schema_version' doesn't exist (1146)
See https://dev.mysql.com/doc/refman/en/mysql-innodb-cluster-creating.html for instructions on setting up a MySQL Server to act as an InnoDB Cluster Metadata server
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原因： 没有创建InnoDB Cluster集群，创建InnoDB Cluster集群后会自动生成这张表。mysql_innodb_cluster_metadata.schema_version表的用途是MySQL Router在进行调度分配的时候，需要读取这张表的内容来做调度策略。
解决办法： 创建InnoDB Cluster集群
6.4启动MySQL Router hang住不动，查看日志报错Error: bootstrap_server_addresses is not allowed when dynamic state file is used
具体如下：
[root@node2 log]# tailf /root/mysqlrouter/log/mysqlrouter.log
2019-08-02 15:37:52 routing INFO [7f9721e2d700] [routing:st_default_ro] started: listening using /root/mysqlrouter/mysqlro.sock
2019-08-02 15:37:52 routing INFO [7f972162c700] [routing:st_default_rw] started: listening using /root/mysqlrouter/mysql.sock
2019-08-02 15:37:52 routing INFO [7f9720e2b700] [routing:st_default_x_ro] started: listening using /root/mysqlrouter/mysqlxro.sock
2019-08-02 15:37:52 routing INFO [7f9713fff700] [routing:st_default_x_rw] started: listening on 0.0.0.0:64460, routing strategy = first-available
2019-08-02 15:37:52 routing INFO [7f9713fff700] [routing:st_default_x_rw] started: listening using /root/mysqlrouter/mysqlx.sock
2019-08-02 15:37:52 routing INFO [7f9713fff700] [routing:st_default_x_rw] stopped
2019-08-02 15:37:52 routing INFO [7f9721e2d700] [routing:st_default_ro] stopped
2019-08-02 15:37:52 routing INFO [7f972162c700] [routing:st_default_rw] stopped
2019-08-02 15:37:52 routing INFO [7f9720e2b700] [routing:st_default_x_ro] stopped
2019-08-02 15:37:52 main ERROR [7f9726f1b880] Error: bootstrap_server_addresses is not allowed when dynamic state file is used
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原因： 开启了dynamic_state
解决办法： 在配置文件中注释掉dynamic_state所在行，例如下列第11行
1 # File automatically generated during MySQL Router bootstrap
2 [DEFAULT]
3 user=root
4 logging_folder=/root/mysqlrouter/log
5 runtime_folder=/root/mysqlrouter/run
6 data_folder=/root/mysqlrouter/data
7 keyring_path=/root/mysqlrouter/data/keyring
8 master_key_path=/root/mysqlrouter/mysqlrouter.key
9 connect_timeout=15
10 read_timeout=30
11 #dynamic_state=/root/mysqlrouter/data/state.json
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6.5启动MySQL Router hang住不动，查看日志报错Unable to fetch live group_replication member data from any server in replicaset 'default'
具体如下：
[root@node2 log]# tailf /root/mysqlrouter/log/mysqlrouter.log
2019-08-02 15:46:41 metadata_cache WARNING [7f3030405700] While updating metadata, could not establish a connection to replicaset 'default' through test61:3306
2019-08-02 15:46:51 metadata_cache WARNING [7f3030405700] While updating metadata, could not establish a connection to replicaset 'default' through oratest52:3306
2019-08-02 15:47:01 metadata_cache WARNING [7f3030405700] While updating metadata, could not establish a connection to replicaset 'default' through oratest51:3306
2019-08-02 15:47:01 metadata_cache ERROR [7f3030405700] Unable to fetch live group_replication member data from any server in replicaset 'default'
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原因： MySQL Router所在节点没有配置本机DNS解析
解决办法： 在/etc/hosts中添加MGR实例的解析
七、个人总结
- MySQL Router有两种部署模式：
- bootstrap模式：支持failover，必须结合InnoDB Cluster使用，在
--directory指定的路径下自动生成安装目录，配置文件里的端口为6446和6447。
- 简单模式：不支持failover，无需结合InnoDB Cluster使用，一般在主从复制或者主主复制等模式下使用，使用
/usr/local/mysqlrouter/share/doc/mysqlrouter/sample_mysqlrouter.conf这个配置文件部署。
- MySQL Router使用的是一个IP地址(可以理解为VIP)加一个RW端口和一个RO端口实现读写分离，Router自身不能判断应用程序的请求是读还是写，因此做读写分离时，必须指定两个端口，如果应用程序不便指定两个端口，也可以全部指定RW端口，这样的话从节点就只作高可用，不做读写分离。
- MySQL Router自身存在单点故障隐患，官方推荐在每个应用程序所在机器上部署Router，本机器连接本机器的Router。也可以在Router的上层在搭建一个高可用服务，如果是自建机房可以选择Keepalived、pacemaker等方案；
- 通过bootstrap生成的配置文件，只需要在
bootstrap_server_addresses这一栏里配置就可以了，格式如下：bootstrap_server_addresses=mysql://oratest51:3306,mysql://oratest52:3306,mysql://test61:3306
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- MySQL Router的后端MySQL实例挂掉之后，无需人工干预，MySQL Router会自动剔除挂了的MySQL实例，当挂了的MySQL实例恢复后会自动加入MySQL Router的后端服务器，也无需人工干预。
- MGR架构可以实现高可用，但是要实现failover，则需要安装InnoDB Cluster了。MySQL Shell和MySQL Router是InnoDB Cluster集群的一部分
- MySQL Router非常轻量级，性能损耗小于1%，官方建议每台应用上部署一个mysqlrouter节点，优点是节省网络带宽。缺点是mysqlrouter太轻量级了，只能提供简单的基于端口的读写路由(Port based routing)和基于权重轮询的负载均衡(Weighted Balance)，不支持基于SQL的读写分离(Query based routing)和空闲优先的负载均衡(Application Layer balancer)
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