Galera Cluster特点
多主架构：真正的多点读写的集群，在任何时候读写数据，都是最新的
同步复制：集群不同节点之间数据同步，没有延迟，在数据库挂掉之后，数据不会丢失
并发复制：从节点APPLY数据时，支持并行执行，更好的性能
故障切换：在出现数据库故障时，因支持多点写入，切换容易
热插拔：在服务期间，如果数据库挂了，只要监控程序发现的够快，不可服务时间就会非常少。在
节点故障期间，节点本身对集群的影响非常小
自动节点克隆：在新增节点，或者停机维护时，增量数据或者基础数据不需要人工手动备份提供，
Galera Cluster会自动拉取在线节点数据，最终集群会变为一致
对应用透明：集群的维护，对应用程序是透明的
Galera Cluster 缺点
由于DDL 需全局验证通过，则集群性能由集群中最差性能节点决定（一般集群节点配置都是一样
的）
新节点加入或延后较大的节点重新加入需全量拷贝数据(SST，State Snapshot Transfer),作为
donor( 贡献者，如： 同步数据时的提供者)的节点在同步过程中无法提供读写
只支持innodb存储引擎的表
PXC最常使用如下4个端口号：
3306：数据库对外服务的端口号
4444：请求SST的端口号
4567：组成员之间进行沟通的端口号
4568：用于传输IST的端口号
下面是MyCat结合PXC的架构图
PXC：Percona XtraDB Cluster，是Percona对Galera的实现
参考仓库：
https://mirrors.tuna.tsinghua.edu.cn/percona/release/$releasever/RPMS/$basearch
案例：Percona XtraDB Cluster(PXC 5.7）
1 环境准备
四台主机
pxc1:172.31.0.7
pxc2:172.31.0.17
pxc3:172.31.0.27
pxc4:172.31.0.37
OS 版本目前不支持CentOS 8
关闭防火墙和SELinux，保证时间同步
注意：如果已经安装MySQL，必须卸载
此处使用清华大学yum源，官方源太慢了
[root@localhost ~]# vim /etc/yum.repos.d/pxc.repo
[percona]
name=percona-repo
baseurl=https://mirrors.tuna.tsinghua.edu.cn/percona/release/$releasever/RPMS/$basearch
enabled=1
gpgcheck=0
# 把镜像源拷贝到远端服务器
[root@localhost ~]# scp /etc/yum.repos.d/pxc.repo 172.31.0.17:/etc/yum.repos.d/
[root@localhost ~]# scp /etc/yum.repos.d/pxc.repo 172.31.0.27:/etc/yum.repos.d/
# 在三个节点都安装好PXC 5.7
[root@localhost ~]# yum install Percona-XtraDB-Cluster-57 -y
[root@localhost ~]# yum install Percona-XtraDB-Cluster-57 -y
[root@localhost ~]# yum install Percona-XtraDB-Cluster-57 -y
在各个节点上分别配置mysql及集群配置文件
/etc/my.cnf为主配置文件，当前版本中，其余的配置文件都放在/etc/percona-xtradb-cluster.conf.d目
录里，包括mysqld.cnf，mysqld_safe.cnf，wsrep.cnf 三个文件
# 主配置文件不需要修改
[root@localhost ~]# vim /etc/my.cnf
# 各个节点改id号即可
[root@localhost ~]# vim /etc/percona-xtradb-cluster.conf.d/mysqld.cnf
# Template my.cnf for PXC
# Edit to your requirements.
[client]
socket=/var/lib/mysql/mysql.sock
[mysqld]
server-id=17
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
log-bin
log_slave_updates
expire_logs_days=7
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# PXC的配置文件必须修改
# 172.31.0.17
[root@localhost ~]# grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://172.31.0.17,172.31.0.27,172.31.0.37 # 各个节点IP
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=172.31.0.17 # 本机ip
wsrep_cluster_name=pxc-cluster-m520
wsrep_node_name=pxc-cluster-node-1-m520 # 各个节点指定的ID
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:s3cretPass"
# 172.31.0.27
[root@localhost ~]# grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://172.31.0.17,172.31.0.27,172.31.0.37
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=172.31.0.27
wsrep_cluster_name=pxc-cluster-m520
wsrep_node_name=pxc-cluster-node-2-m520 # 各个节点指定的ID
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:s3cretPass" # 取消注释
# 172.31.0.37
[root@localhost ~]# grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://172.31.0.17,172.31.0.27,172.31.0.27
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=172.31.0.37
wsrep_cluster_name=pxc-cluster-m520
wsrep_node_name=pxc-cluster-node-3-m520
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:s3cretPass"
注意：尽管Galera Cluster不再需要通过binlog的形式进行同步，但还是建议在配置文件中开启二进制日
志功能，原因是后期如果有新节点需要加入，老节点通过SST全量传输的方式向新节点传输数据，很可
能会拖垮集群性能，所以让新节点先通过binlog方式完成同步后再加入集群会是一种更好的选择
配置文件各项配置意义
| 配置 | 说明 |
|---|---|
| wsrep_provider | 指定Galera库的路径 |
| wsrep_cluster_name | Galera集群的名称 |
| wsrep_cluster_address | Galera集群中各节点地址。地址使用组通信协议gcomm://(groupcommunication) |
| wsrep_node_name | 本节点在Galera集群中的名称 |
| wsrep_node_address | 本节点在Galera集群中的通信地址 |
| wsrep_sst_method | state_snapshot_transfer(SST)使用的传输方法，可用方法有mysqldump、rsync和xtrabackup，前两者在传输时都需要对Donor加全局只读锁(FLUSH TABLES WITH READLOCK)，xtrabackup则不需要(它使用percona自己提供的backup lock)。强烈建议采用xtrabackup |
| wsrep_sst_auth | 在SST传输时需要用到的认证凭据，格式为："用户：密码" |
| pxc_strict_mode | 是否限制PXC启用正在试用阶段的功能，ENFORCING是默认值，表示不启用 |
| binlog_format | 二进制日志的格式。Galera只支持row格式的二进制日志 |
| default_storage_engine | 指定默认存储引擎。Galera的复制功能只支持InnoDB |
| innodb_autoinc_lock_mode | 只能设置为2，设置为0或1时会无法正确处理死锁问题 |
启动PXC集群中任意的节点可以作为第一节点
[root@localhost ~]# systemctl start mysql@bootstrap.service
# 查看端口有4567和3306
[root@localhost ~]# ss -tunl
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 128 *:4567 *:*
tcp LISTEN 0 100 127.0.0.1:25 *:*
tcp LISTEN 0 80 :::3306 :::*
tcp LISTEN 0 128 :::22 :::*
tcp LISTEN 0 100 ::1:25 :::*
# 查看root密码
[root@localhost ~]# grep "temporary password" /var/log/mysqld.log
2021-05-22T13:50:17.837284Z 1 [Note] A temporary password is generated for root@localhost: +Egpg69fijV%
[root@localhost ~]# mysql -uroot -p'+Egpg69fijV%'
# 修改root密码
mysql> alter user 'root'@'localhost' identified by 'centos';
Query OK, 0 rows affected (0.00 sec)
# 创建相关用户并授权
mysql> create user 'sstuser'@'localhost' identified by 's3cretPass';
Query OK, 0 rows affected (0.01 sec)
# 授权
mysql> grant reload,lock tables,process,replication client on *.* to 'sstuser'@'localhost';
Query OK, 0 rows affected (0.00 sec)
# 查看相关变量
mysql> show variables like 'wsrep%'G
*************************** 1. row ***************************
Variable_name: wsrep_OSU_method
Value: TOI
*************************** 2. row ***************************
Variable_name: wsrep_RSU_commit_timeout
Value: 5000
*************************** 3. row ***************************
Variable_name: wsrep_auto_increment_control
Value: ON
*************************** 4. row ***************************
Variable_name: wsrep_causal_reads
Value: OFF
*************************** 5. row ***************************
Variable_name: wsrep_certification_rules
Value: strict
*************************** 6. row ***************************
Variable_name: wsrep_certify_nonPK
Value: ON
*************************** 7. row ***************************
Variable_name: wsrep_cluster_address
Value: gcomm://172.31.0.17,172.31.0.27,172.31.0.37
*************************** 8. row ***************************
Variable_name: wsrep_cluster_name
Value: pxc-cluster
*************************** 9. row ***************************
Variable_name: wsrep_convert_LOCK_to_trx
Value: OFF
*************************** 10. row ***************************
Variable_name: wsrep_data_home_dir
Value: /var/lib/mysql/
*************************** 11. row ***************************
Variable_name: wsrep_dbug_option
Value:
*************************** 12. row ***************************
Variable_name: wsrep_debug
Value: OFF
*************************** 13. row ***************************
Variable_name: wsrep_desync
Value: OFF
*************************** 14. row ***************************
Variable_name: wsrep_dirty_reads
Value: OFF
*************************** 15. row ***************************
Variable_name: wsrep_drupal_282555_workaround
Value: OFF
*************************** 16. row ***************************
Variable_name: wsrep_forced_binlog_format
Value: NONE
*************************** 17. row ***************************
Variable_name: wsrep_load_data_splitting
Value: ON
*************************** 18. row ***************************
Variable_name: wsrep_log_conflicts
Value: ON
*************************** 19. row ***************************
Variable_name: wsrep_max_ws_rows
Value: 0
*************************** 20. row ***************************
Variable_name: wsrep_max_ws_size
Value: 2147483647
*************************** 21. row ***************************
Variable_name: wsrep_mode
Value:
*************************** 22. row ***************************
Variable_name: wsrep_node_address
Value: 172.31.0.17
*************************** 23. row ***************************
Variable_name: wsrep_node_incoming_address
Value: AUTO
*************************** 24. row ***************************
Variable_name: wsrep_node_name
Value: pxc-cluster-node-1
*************************** 25. row ***************************
Variable_name: wsrep_notify_cmd
Value:
*************************** 26. row ***************************
Variable_name: wsrep_on
Value: ON
*************************** 27. row ***************************
Variable_name: wsrep_preordered
Value: OFF
*************************** 28. row ***************************
Variable_name: wsrep_provider
Value: /usr/lib64/galera3/libgalera_smm.so
*************************** 29. row ***************************
Variable_name: wsrep_provider_options
Value: base_dir = /var/lib/mysql/; base_host = 172.31.0.17; base_port = 4567; cert.log_conflicts = no; cert.optimistic_pa = yes; debug = no; evs.auto_evict = 0; evs.causal_keepalive_period = PT1S; evs.debug_log_mask = 0x1; evs.delay_margin = PT1S; evs.delayed_keep_period = PT30S; evs.inactive_check_period = PT0.5S; evs.inactive_timeout = PT15S; evs.info_log_mask = 0; evs.install_timeout = PT7.5S; evs.join_retrans_period = PT1S; evs.keepalive_period = PT1S; evs.max_install_timeouts = 3; evs.send_window = 10; evs.stats_report_period = PT1M; evs.suspect_timeout = PT5S; evs.use_aggregate = true; evs.user_send_window = 4; evs.version = 0; evs.view_forget_timeout = P1D; gcache.dir = /var/lib/mysql/; gcache.freeze_purge_at_seqno = -1; gcache.keep_pages_count = 0; gcache.keep_pages_size = 0; gcache.mem_size = 0; gcache.name = /var/lib/mysql//galera.cache; gcache.page_size = 128M; gcache.recover = no; gcache.size = 128M; gcomm.thread_prio = ; gcs.fc_debug = 0; gcs.fc_factor = 1; gcs.fc_limit = 100; gcs.fc_master_slave = no;
*************************** 30. row ***************************
Variable_name: wsrep_recover
Value: OFF
*************************** 31. row ***************************
Variable_name: wsrep_reject_queries
Value: NONE
*************************** 32. row ***************************
Variable_name: wsrep_replicate_myisam
Value: OFF
*************************** 33. row ***************************
Variable_name: wsrep_restart_slave
Value: OFF
*************************** 34. row ***************************
Variable_name: wsrep_retry_autocommit
Value: 1
*************************** 35. row ***************************
Variable_name: wsrep_slave_FK_checks
Value: ON
*************************** 36. row ***************************
Variable_name: wsrep_slave_UK_checks
Value: OFF
*************************** 37. row ***************************
Variable_name: wsrep_slave_threads
Value: 8
*************************** 38. row ***************************
Variable_name: wsrep_sst_allowed_methods
Value: mysqldump,rsync,skip,xtrabackup,xtrabackup-v2
*************************** 39. row ***************************
Variable_name: wsrep_sst_auth
Value: ********
*************************** 40. row ***************************
Variable_name: wsrep_sst_donor
Value:
*************************** 41. row ***************************
Variable_name: wsrep_sst_donor_rejects_queries
Value: OFF
*************************** 42. row ***************************
Variable_name: wsrep_sst_method
Value: xtrabackup-v2
*************************** 43. row ***************************
Variable_name: wsrep_sst_receive_address
Value: AUTO
*************************** 44. row ***************************
Variable_name: wsrep_start_position
Value: 00000000-0000-0000-0000-000000000000:-1
*************************** 45. row ***************************
Variable_name: wsrep_sync_wait
Value: 0
45 rows in set (0.01 sec)
# 查看相关状态变量
mysql> show status like 'wsrep%'G
*************************** 1. row ***************************
Variable_name: wsrep_local_state_uuid
Value: a9af3ceb-bb04-11eb-8cd1-d26e25aee8cd
*************************** 2. row ***************************
Variable_name: wsrep_protocol_version
Value: 9
*************************** 3. row ***************************
Variable_name: wsrep_last_applied
Value: 3
*************************** 4. row ***************************
Variable_name: wsrep_last_committed
Value: 3
*************************** 5. row ***************************
Variable_name: wsrep_replicated
Value: 3
*************************** 6. row ***************************
Variable_name: wsrep_replicated_bytes
Value: 752
*************************** 7. row ***************************
Variable_name: wsrep_repl_keys
Value: 3
*************************** 8. row ***************************
Variable_name: wsrep_repl_keys_bytes
Value: 96
*************************** 9. row ***************************
Variable_name: wsrep_repl_data_bytes
Value: 460
*************************** 10. row ***************************
Variable_name: wsrep_repl_other_bytes
Value: 0
*************************** 11. row ***************************
Variable_name: wsrep_received
Value: 2
*************************** 12. row ***************************
Variable_name: wsrep_received_bytes
Value: 153
*************************** 13. row ***************************
Variable_name: wsrep_local_commits
Value: 0
*************************** 14. row ***************************
Variable_name: wsrep_local_cert_failures
Value: 0
*************************** 15. row ***************************
Variable_name: wsrep_local_replays
Value: 0
*************************** 16. row ***************************
Variable_name: wsrep_local_send_queue
Value: 0
*************************** 17. row ***************************
Variable_name: wsrep_local_send_queue_max
Value: 1
*************************** 18. row ***************************
Variable_name: wsrep_local_send_queue_min
Value: 0
*************************** 19. row ***************************
Variable_name: wsrep_local_send_queue_avg
Value: 0.000000
*************************** 20. row ***************************
Variable_name: wsrep_local_recv_queue
Value: 0
*************************** 21. row ***************************
Variable_name: wsrep_local_recv_queue_max
Value: 2
*************************** 22. row ***************************
Variable_name: wsrep_local_recv_queue_min
Value: 0
*************************** 23. row ***************************
Variable_name: wsrep_local_recv_queue_avg
Value: 0.500000
*************************** 24. row ***************************
Variable_name: wsrep_local_cached_downto
Value: 1
*************************** 25. row ***************************
Variable_name: wsrep_flow_control_paused_ns
Value: 0
*************************** 26. row ***************************
Variable_name: wsrep_flow_control_paused
Value: 0.000000
*************************** 27. row ***************************
Variable_name: wsrep_flow_control_sent
Value: 0
*************************** 28. row ***************************
Variable_name: wsrep_flow_control_recv
Value: 0
*************************** 29. row ***************************
Variable_name: wsrep_flow_control_interval
Value: [ 100, 100 ]
*************************** 30. row ***************************
Variable_name: wsrep_flow_control_interval_low
Value: 100
*************************** 31. row ***************************
Variable_name: wsrep_flow_control_interval_high
Value: 100
*************************** 32. row ***************************
Variable_name: wsrep_flow_control_status
Value: OFF
*************************** 33. row ***************************
Variable_name: wsrep_flow_control_active
Value: false
*************************** 34. row ***************************
Variable_name: wsrep_flow_control_requested
Value: false
*************************** 35. row ***************************
Variable_name: wsrep_cert_deps_distance
Value: 1.000000
*************************** 36. row ***************************
Variable_name: wsrep_apply_oooe
Value: 0.000000
*************************** 37. row ***************************
Variable_name: wsrep_apply_oool
Value: 0.000000
*************************** 38. row ***************************
Variable_name: wsrep_apply_window
Value: 1.000000
*************************** 39. row ***************************
Variable_name: wsrep_commit_oooe
Value: 0.000000
*************************** 40. row ***************************
Variable_name: wsrep_commit_oool
Value: 0.000000
*************************** 41. row ***************************
Variable_name: wsrep_commit_window
Value: 1.000000
*************************** 42. row ***************************
Variable_name: wsrep_local_state
Value: 4
*************************** 43. row ***************************
Variable_name: wsrep_local_state_comment
Value: Synced
*************************** 44. row ***************************
Variable_name: wsrep_cert_index_size
Value: 1
*************************** 45. row ***************************
Variable_name: wsrep_cert_bucket_count
Value: 22
*************************** 46. row ***************************
Variable_name: wsrep_gcache_pool_size
Value: 2192
*************************** 47. row ***************************
Variable_name: wsrep_causal_reads
Value: 0
*************************** 48. row ***************************
Variable_name: wsrep_cert_interval
Value: 0.000000
*************************** 49. row ***************************
Variable_name: wsrep_open_transactions
Value: 0
*************************** 50. row ***************************
Variable_name: wsrep_open_connections
Value: 0
*************************** 51. row ***************************
Variable_name: wsrep_ist_receive_status
Value:
*************************** 52. row ***************************
Variable_name: wsrep_ist_receive_seqno_start
Value: 0
*************************** 53. row ***************************
Variable_name: wsrep_ist_receive_seqno_current
Value: 0
*************************** 54. row ***************************
Variable_name: wsrep_ist_receive_seqno_end
Value: 0
*************************** 55. row ***************************
Variable_name: wsrep_incoming_addresses
Value: 172.31.0.17:3306
*************************** 56. row ***************************
Variable_name: wsrep_cluster_weight
Value: 1
*************************** 57. row ***************************
Variable_name: wsrep_desync_count
Value: 0
*************************** 58. row ***************************
Variable_name: wsrep_evs_delayed
Value:
*************************** 59. row ***************************
Variable_name: wsrep_evs_evict_list
Value:
*************************** 60. row ***************************
Variable_name: wsrep_evs_repl_latency
Value: 0/0/0/0/0
*************************** 61. row ***************************
Variable_name: wsrep_evs_state
Value: OPERATIONAL
*************************** 62. row ***************************
Variable_name: wsrep_gcomm_uuid
Value: a9ae769b-bb04-11eb-83d4-c3d7162c47bc
*************************** 63. row ***************************
Variable_name: wsrep_gmcast_segment
Value: 0
*************************** 64. row ***************************
Variable_name: wsrep_cluster_conf_id
Value: 1
*************************** 65. row ***************************
Variable_name: wsrep_cluster_size
Value: 1
*************************** 66. row ***************************
Variable_name: wsrep_cluster_state_uuid
Value: a9af3ceb-bb04-11eb-8cd1-d26e25aee8cd
*************************** 67. row ***************************
Variable_name: wsrep_cluster_status
Value: Primary
*************************** 68. row ***************************
Variable_name: wsrep_connected
Value: ON
*************************** 69. row ***************************
Variable_name: wsrep_local_bf_aborts
Value: 0
*************************** 70. row ***************************
Variable_name: wsrep_local_index
Value: 0
*************************** 71. row ***************************
Variable_name: wsrep_provider_name
Value: Galera
*************************** 72. row ***************************
Variable_name: wsrep_provider_vendor
Value: Codership Oy <info@codership.com>
*************************** 73. row ***************************
Variable_name: wsrep_provider_version
Value: 3.49(r0ef0d79)
*************************** 74. row ***************************
Variable_name: wsrep_ready
Value: ON
74 rows in set (0.00 sec)
## 重点关注下面内容
mysql> show status like 'wsrep%';
+----------------------------------+--------------------------------------+
| Variable_name | Value |
+----------------------------------+--------------------------------------+
| wsrep_local_state_uuid | a9af3ceb-bb04-11eb-8cd1-d26e25aee8cd |
... |...
| wsrep_local_state | 4 |
| wsrep_local_state_comment | Synced |
... |...
| wsrep_cluster_size | 1 |
| wsrep_cluster_status | Primary |
| wsrep_connected | ON |
... |...
| wsrep_ready | ON |
+----------------------------------+--------------------------------------+
74 rows in set (0.00 sec)
# 说明：
wsrep_cluster_size表示，该Galera集群中只有一个节点
wsrep_local_state_comment 状态为Synced(4)，表示数据已同步完成(因为是第一个引导节点，无数据
需要同步)。 如果状态是Joiner, 意味着 SST 没有完成. 只有所有节点状态是Synced，才可以加新节点
wsrep_cluster_status为Primary，且已经完全连接并准备好
启动PXC集群中其它所有节点
# 除了名义上的master之外，其它的node节点只需要启动mysql即可
[root@localhost ~]# systemctl start mysql
查看集群状态，验证集群是否成功
#在任意节点，查看集群状态
mysql> show variables like 'wsrep_node_name';
+-----------------+-------------------------+
| Variable_name | Value |
+-----------------+-------------------------+
| wsrep_node_name | pxc-cluster-node-1-m520 |
+-----------------+-------------------------+
1 row in set (0.00 sec)
mysql> show variables like 'wsrep_node_address';
+--------------------+-------------+
| Variable_name | Value |
+--------------------+-------------+
| wsrep_node_address | 172.31.0.17 |
+--------------------+-------------+
1 row in set (0.00 sec)
mysql> show variables like 'wsrep_on';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wsrep_on | ON |
+---------------+-------+
1 row in set (0.00 sec)
# 查看集群成员个数
mysql> show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 1 |
+--------------------+-------+
1 row in set (0.00 sec)
# 在任意节点查看数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
# 在任意节点创建数据库
[root@localhost mysql]# mysql -uroot -pcentos
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 11
Server version: 5.7.33-36-57-log Percona XtraDB Cluster (GPL), Release rel36, Revision a1ed9c3, WSREP version 31.49, wsrep_31.49
Copyright (c) 2009-2021 Percona LLC and/or its affiliates
Copyright (c) 2000, 2021, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.01 sec)
mysql> create database db1;
Query OK, 1 row affected (0.00 sec)
# 其他任意节点查询可以看到创建的db1库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
# 上面的节点添加完，在任意节点执行可以查看集群的个数
mysql> show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 3 |
+--------------------+-------+
1 row in set (0.00 sec)
扩展
在PXC集群中加入节点
一个节点加入到Galera集群有两种情况：新节点加入集群、暂时离组的成员再次加入集群
1）新节点加入Galera集群
新节点加入集群时，需要从当前集群中选择一个Donor节点来同步数据，也就是所谓的
state_snapshot_tranfer(SST)过程。SST同步数据的方式由选项wsrep_sst_method决定，一般选择的是
xtrabackup。
必须注意，新节点加入Galera时，会删除新节点上所有已有数据，再通过xtrabackup(假设使用的是该方
式)从Donor处完整备份所有数据进行恢复。所以，如果数据量很大，新节点加入过程会很慢。而且，在
一个新节点成为Synced状态之前，不要同时加入其它新节点，否则很容易将集群压垮。
如果是这种情况，可以考虑使用wsrep_sst_method=rsync来做增量同步，既然是增量同步，最好保证
新节点上已经有一部分数据基础，否则和全量同步没什么区别，且这样会对Donor节点加上全局read
only锁。
2）旧节点加入Galera集群
如果旧节点加入Galera集群，说明这个节点在之前已经在Galera集群中呆过，有一部分数据基础，缺少
的只是它离开集群时的数据。这时加入集群时，会采用IST(incremental snapshot transfer)传输机制，
即使用增量传输。
但注意，这部分增量传输的数据源是Donor上缓存在GCache文件中的，这个文件有大小限制，如果缺失
的数据范围超过已缓存的内容，则自动转为SST传输。如果旧节点上的数据和Donor上的数据不匹配(例
如这个节点离组后人为修改了一点数据)，则自动转为SST传输。
在PXC集群中再加一台新的主机PXC4：172.31.0.47
[root@localhost ~]# yum install Percona-XtraDB-Cluster-57 -y
# 改配置文件
[root@localhost ~]# vim /etc/percona-xtradb-cluster.conf.d/mysqld.cnf
[client]
socket=/var/lib/mysql/mysql.sock
[mysqld]
server-id=47
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
log-bin
log_slave_updates
expire_logs_days=7
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
# 改配置文件(添加新的节点需要每台都把ip加上)
[root@localhost ~]# grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://172.31.0.17:4567,172.31.0.27:4567,172.31.0.37:4567,172.31.0.47
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=172.31.0.47
wsrep_cluster_name=pxc-cluster-m520
wsrep_node_name=pxc-cluster-node-4-m520
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:s3cretPass"
# 启动
[root@localhost ~]# systemctl start mysql
# 查看端口4567和3306
[root@localhost ~]# ss -tnul
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 128 *:4567 *:*
tcp LISTEN 0 100 127.0.0.1:25 *:*
tcp LISTEN 0 80 :::3306 :::*
tcp LISTEN 0 128 :::22 :::*
tcp LISTEN 0 100 ::1:25 :::*
任意节点查询会发现从3变成了4，说明已经添加成功
mysql> show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 4 |
+--------------------+-------+
1 row in set (0.01 sec)
在除第一个启动节点外的任意节点停止服务
[root@localhost ~]# systemctl stop mysql
# 在其它任意节点查看wsrep_cluster_size变量少了一个节点
mysql> show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 3 |
+--------------------+-------+
1 row in set (0.00 sec)
报错
启动从服务报错
[root@localhost ~]# vim /var/log/mysqld.log
2021-05-22T15:42:13.975755Z 0 [Warning] WSREP: last inactive check more than PT1.5S (3*evs.inactive_check_period) ago (PT3.50712S), skipping check
2021-05-22T15:42:43.527512Z 0 [Note] WSREP: Current view of cluster as seen by this node
view ((empty))
2021-05-22T15:42:43.527657Z 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():161
2021-05-22T15:42:43.527671Z 0 [ERROR] WSREP: gcs/src/gcs_core.cpp:gcs_core_open():209: Failed to open backend connection: -110 (Connection timed out)
2021-05-22T15:42:43.527949Z 0 [ERROR] WSREP: gcs/src/gcs.cpp:gcs_open():1527: Failed to open channel 'pxc-cluster' at 'gcomm://172.31.0.17,172.31.0.27,172.31.0.37': -110 (Connection timed out)
2021-05-22T15:42:43.527962Z 0 [ERROR] WSREP: gcs connect failed: Connection timed out
2021-05-22T15:42:43.527968Z 0 [ERROR] WSREP: Provider/Node (gcomm://172.31.0.17,172.31.0.27,172.31.0.37) failed to establish connection with cluster (reason: 7)
2021-05-22T15:42:43.527973Z 0 [ERROR] Aborting
2021-05-22T15:42:43.527981Z 0 [Note] Giving 0 client threads a chance to die gracefully
2021-05-22T15:42:43.527988Z 0 [Note] WSREP: Waiting for active wsrep applier to exit
2021-05-22T15:42:43.528011Z 0 [Note] WSREP: Service disconnected.
2021-05-22T15:42:43.528015Z 0 [Note] WSREP: Waiting to close threads......
2021-05-22T15:42:48.528984Z 0 [Note] WSREP: Some threads may fail to exit.
2021-05-22T15:42:48.535147Z 0 [Note] WSREP: Service thread queue flushed.
2021-05-22T15:42:48.535255Z 0 [Note] WSREP: MemPool(SlaveTrxHandle): hit ratio: 0, misses: 0, in use: 0, in pool: 0
2021-05-22T15:42:48.535398Z 0 [Note] WSREP: Shifting CLOSED -> DESTROYED (TO: 0)
2021-05-22T15:42:48.536037Z 0 [Note] Binlog end
2021-05-22T15:42:48.536169Z 0 [Note] /usr/sbin/mysqld: Shutdown complete
上面其他节点启动报错问题解决方法：
其他节点配置文件加上4567端口（组成员之间进行沟通的端口号），启动mysql服务即可
[root@localhost ~]# vim /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
wsrep_cluster_address=gcomm://172.31.0.17:4567,172.31.0.27:4567,172.31.0.37:4567
安装软件Percona-XtraDB-Cluster-57报错
Error: percona-xtrabackup-24 conflicts with percona-xtrabackup-2.3.10-1.el7.x86_64
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
解决思路：因为曾经做实验安装过相关的软件造成冲突了，卸载然后再重新安装即可
[root@localhost ~]# yum remove percona-xtrabackup* -y