2018-08-09 mariadb galera cluster

mariadb install

利用 respository tool 获取需要的 mariadb 版本对应的仓库，并完成安装

https://downloads.mariadb.org/mariadb/repositories/

sudo apt-get install software-properties-common 
sudo apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xcbcb082a1bb943db
sudo add-apt-repository 'deb [arch=amd64,i386,ppc64el] http://mirrors.neusoft.edu.cn/mariadb/repo/10.1/ubuntu trusty main'

sudo apt-get update
sudo apt-get install mariadb-server

galera cluster setup

创建单点 cluster

可以通过以下命令新创建一个 galera cluster 集群

mysqld --wsrep-new-cluster

通过 mysql 命令来查看当前集群的状态：

show status like 'wsrep_%';

显示集群的 wsrep_cluster_size = 0， wsrep_cluster_status = DISCONNECTED，表明node并未加入到 cluster 中。这是因为，需要在修改 mariadb 配置，来开启 wsrep

[galera]
# Mandatory settings
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
wsrep_cluster_address="gcomm://10.240.140.2,10.240.140.3"
binlog_format=row
#default_storage_engine=InnoDB
#innodb_autoinc_lock_mode=2

修改后重启，查看状态

MariaDB [(none)]> show status like 'wsrep_%';
+------------------------------+--------------------------------------+
| Variable_name                | Value                                |
+------------------------------+--------------------------------------+
| wsrep_apply_oooe             | 0.000000                             |
| wsrep_apply_oool             | 0.000000                             |
| wsrep_apply_window           | 0.000000                             |
| wsrep_causal_reads           | 0                                    |
| wsrep_cert_deps_distance     | 0.000000                             |
| wsrep_cert_index_size        | 0                                    |
| wsrep_cert_interval          | 0.000000                             |
| wsrep_cluster_conf_id        | 5                                    |
| wsrep_cluster_size           | 1                                    |
| wsrep_cluster_state_uuid     | 11204c5f-9ba9-11e8-a8dc-2acc1cebe53a |
| wsrep_cluster_status         | Primary                              |
| wsrep_commit_oooe            | 0.000000                             |
| wsrep_commit_oool            | 0.000000                             |
| wsrep_commit_window          | 0.000000                             |
| wsrep_connected              | ON                                   |
| wsrep_desync_count           | 0                                    |
...

添加 node

和上述类似，需要修改 mariadb 配置

[galera]
# Mandatory settings
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
wsrep_cluster_address="gcomm://10.240.140.2,10.240.140.3"
binlog_format=row
#default_storage_engine=InnoDB
#innodb_autoinc_lock_mode=2

再将该新节点加入到现有的 cluster 中

mysqld --wsrep_cluster_address=gcomm://10.240.140.2

重启 node，添加成功后，输入命令查看：

MariaDB [(none)]> show status like 'wsrep_%';
+------------------------------+---------------------------------------+
| Variable_name                | Value                                 |
+------------------------------+---------------------------------------+
| wsrep_apply_oooe             | 0.000000                              |
| wsrep_apply_oool             | 0.000000                              |
| wsrep_apply_window           | 0.000000                              |
| wsrep_causal_reads           | 0                                     |
| wsrep_cert_deps_distance     | 0.000000                              |
| wsrep_cert_index_size        | 0                                     |
| wsrep_cert_interval          | 0.000000                              |
| wsrep_cluster_conf_id        | 2                                     |
| wsrep_cluster_size           | 2                                     |
| wsrep_cluster_state_uuid     | 846ec2c8-9bb5-11e8-95c5-12bbe81db3ef  |
| wsrep_cluster_status         | Primary                               |
| wsrep_commit_oooe            | 0.000000                              |
| wsrep_commit_oool            | 0.000000                              |
| wsrep_commit_window          | 0.000000                              |
| wsrep_connected              | ON                                    |
| wsrep_desync_count           | 0                                     |
...

注意到 wsrep_cluster_size = 2 表明该 cluster 中当前有 2 个节点。可以通过相同的方式添加新节点保证 2n+1（n=1, 2, 3...） 个节点

测试

通过在任一 node 上进行数据库操作，观察其他 node 的同步情况。如果同步成功，表明创建mariadb galera cluster 成功。

参考链接：

1. https://mariadb.com/kb/en/library/getting-started-with-mariadb-galera-cluster/
2. https://serverfault.com/questions/744040/unable-to-run-a-mariadb-10-1-galera-cluster
3. http://galeracluster.com/documentation-webpages/monitoringthecluster.html