MySQL5.7之PXC集群搭建
系统：centos7
内存：2G
磁盘：128G
IP地址：192.168.0.201（第一节点）
192.168.0.202
192.168.0.203
#vi /etc/selinux/config
SELINUX=disabled #修改该项为disabled
#执行命令 setenforce 0
#systemctl restart firewalld
开放防火墙这4个端口
firewall-cmd --add-port=4444/tcp --permanent
firewall-cmd --add-port=4567/tcp --permanent
firewall-cmd --add-port=4568/tcp --permanent
firewall-cmd --add-port=3306/tcp --permanent
安装集群
#yum -y install http://www.percona.com/downloads/percona-release/redhat/0.1-4/percona-release-0.1-4.noarch.rpm
#yum -y update percona-release
#yum -y install Percona-XtraDB-Cluster-57
启动mysql，并修改密码
service mysql start
grep ‘temporary password‘ /var/log/mysqld.log
[Note] A temporary password is generated for : u8E;M:,p_T&H
#mysql -uroot -pu8E;M:,p_T&H
mysql> update mysql.user set authentication_string=password(‘‘) where user=‘root‘ and Host = ‘localhost‘;
使用下面方式启动第一台机器（201服务器）,这台叫引导节点。
只有这一台是这样启动。别的服务器用service mysql start启动
#ssh 192.168.0.201
#systemctl start
进入mysql
#mysql -uroot
#set wsrep_causal_reads =1; 避免各个节点的数据不一致，这种情况需要等待全同步复制 将此文件复制到master1、master2，注意要把 wsrep_node_name 和 wsrep_node_address 改成相应节点的 hostname 和 ip。
创建配置文件中对应的用户 所有节点的IP都要创建
#mysql -uroot
mysql> grant all privileges on . to ‘pxcuser‘@‘%‘ identified by ‘‘;
报错如下：
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
解决办法：
mysql> set password = password(‘‘);
mysql> grant all privileges on . to ‘pxcuser‘@‘%‘ identified by ‘‘;
mysql> grant all privileges on . to ‘pxcuser‘@‘localhost‘ identified by ‘‘;
mysql> flush privileges;
进入202和203服务器配置
#ssh 192.168.0.203
注意203和202的启动方式
#service mysql start
创建配置文件中对应的用户 所有节点的IP都要创建
mysql> grant all privileges on . to ‘pxcuser‘@‘%‘ identified by ‘‘;
mysql> grant all privileges on . to ‘pxcuser‘@‘localhost‘ identified by ‘‘;
mysql> flush privileges;
注意：服务的启动和停止要对应
service mysql stop ------> 启动时用service mysql start
systemctl stop -----> 启用是用 systemctl start
注意避坑：/var/lib/mysql/grastate.dat文件中safe_to_bootstrap为1的服务器是主库,用主库的方式启动！！我们想让谁做主库也可以手动设置该服务器,而且三台集群的uuid也相同才可以启动。
seqno为-1表示已加入到集群，数据库关闭后seqno会变。
下面这台服务器201做主库启动后，seqno从4变成了-1，表示已经加入集群。
203服务器做从库一直无法启动。
启动方式是：service mysql start
报错信息如下#tail -fn 100 /var/log/mysqld.log
2020-01-10T09:25:56.982598Z 0 [Note] WSREP: (32d9017e, ‘tcp://0.0.0.0:4567‘) turning message relay requesting off
2020-01-10T09:26:23.489499Z 0 [Note] WSREP: (32d9017e, ‘tcp://0.0.0.0:4567‘) turning message relay requesting on, nonlive peers: tcp://192.168.0.202:4567
2020-01-10T09:26:24.489792Z 0 [Note] WSREP: (32d9017e, ‘tcp://0.0.0.0:4567‘) reconnecting to 30d8eb06 (tcp://192.168.0.202:4567), attempt 0
2020-01-10T09:26:24.494967Z 0 [ERROR] WSREP: failed to open gcomm backend connection: 110: failed to reach primary view (pc.wait_prim_timeout): 110 (Connection timed out)
at gcomm/src/pc.cpp:connect():159
2020-01-10T09:26:24.495007Z 0 [ERROR] WSREP: gcs/src/gcs_core.cpp:gcs_core_open():209: Failed to open backend connection: -110 (Connection timed out)
2020-01-10T09:26:24.495376Z 0 [ERROR] WSREP: gcs/src/gcs.cpp:gcs_open():1514: Failed to open channel ‘pxc-cluster-test‘ at ‘gcomm://192.168.0.202,192.168.0.203,192.168.0.201‘: -110 (Connection timed out)
2020-01-10T09:26:24.495402Z 0 [ERROR] WSREP: gcs connect failed: Connection timed out
2020-01-10T09:26:24.495415Z 0 [ERROR] WSREP: Provider/Node (gcomm://192.168.0.202,192.168.0.203,192.168.0.201) failed to establish connection with cluster (reason: 7)
2020-01-10T09:26:24.495423Z 0 [ERROR] Aborting
解决办法：把203服务器的grastate.dat文件的uuid修改的和202，201一模一样就可以启动了。
safe_to_bootstrap: 设置为0
那么UUID是什么呢？
为什么同一个pxc集群的UUID是相同的呢？
验证集群：show status like ‘wsrep%‘;
| wsrep_incoming_addresses | 192.168.0.202:3306,192.168.0.203:3306,192.168.0.201:3306 |
| wsrep_cluster_weight | 3 |
| wsrep_desync_count | 0 |
| wsrep_evs_delayed | |
| wsrep_evs_evict_list | |
| wsrep_evs_repl_latency | 0/0/0/0/0 |
| wsrep_evs_state | OPERATIONAL |
| wsrep_gcomm_uuid | e9e76881-338f-11ea-90d6-3b07eeeaf3a4 |
| wsrep_cluster_conf_id | 3 |
| wsrep_cluster_size | 3 |
| wsrep_cluster_state_uuid | 9d5bc8a5-3374-11ea-9aac-b3599f4e37e4 |
| wsrep_cluster_status | Primary |
| wsrep_connected | ON |
| wsrep_local_bf_aborts | 0 |
| wsrep_local_index | 2 |
| wsrep_provider_name | Galera |
| wsrep_provider_vendor | Codership Oy <> |
| wsrep_provider_version | 3.41(rb3295e6) |
| wsrep_ready | ON