MySQL高可用 Galera Cluster [toc] Galera Cluster Galera Cluster：集成了Galera插件的MySQL集群，是一種新型的，數據不共用的，高度冗餘的高可用方案，目前Galera Cluster有兩個版本，分別是Percona Xtradb Clust ...
目錄
MySQL高可用 Galera Cluster
MySQL高可用 Galera Cluster
Galera Cluster
Galera Cluster：集成了Galera插件的MySQL集群，是一種新型的，數據不共用的，高度冗餘的高可用方案，目前Galera Cluster有兩個版本，分別是Percona Xtradb Cluster及MariaDB Cluster，Galera本身是具有多主特性的，即採用multi-master的集群架構，是一個既穩健，又在數據一致性、完整性及高性能方面有出色表現的高可用解決方案
Galera Cluster特點
• 多主架構：真正的多點讀寫的集群，在任何時候讀寫數據，都是最新的
• 同步複製：集群不同節點之間數據同步，沒有延遲，在資料庫掛掉之後，數據不會丟失
• 併發複製：從節點APPLY數據時，支持並行執行，更好的性能
• 故障切換：在出現資料庫故障時，因支持多點寫入，切換容易
• 熱插拔：在服務期間，如果資料庫掛了，只要監控程式發現的夠快，不可服務時間就會非常少。在節點故障期間，節點本身對集群的影響非常小
• 自動節點克隆：在新增節點，或者停機維護時，增量數據或者基礎數據不需要人工手動備份提供，Galera Cluster會自動拉取線上節點數據，最終集群會變為一致
• 對應用透明：集群的維護，對應用程式是透明的只支持innodb存儲引擎的表Galera Cluster 缺點
• 由於DDL 需全局驗證通過，則集群性能由集群中最差性能節點決定（一般集群節點配置都是一樣的）
• 新節點加入或延後較大的節點重新加入需全量拷貝數據(SST，State Snapshot Transfer),作為donor( 貢獻者，如： 同步數據時的提供者)的節點在同步過程中無法提供讀寫
• 只支持innodb存儲引擎的表Galera Cluster工作過程
Galera Cluster官方文檔
http://galeracluster.com/documentation-webpages/galera-documentation.pdf
http://galeracluster.com/documentation-webpages/index.html
https://www.percona.com/doc/percona-xtradb-cluster/LATEST/index.html
https://mariadb.com/kb/en/library/getting-started-with-mariadb-galera-cluster/
Galera Cluster包括兩個組件
• Galera replication library (galera-3)
• WSREP：MySQL extended with the Write Set ReplicationWSREP複製實現
- PXC：Percona XtraDB Cluster，是Percona對Galera的實現
參考倉庫：
https://mirrors.tuna.tsinghua.edu.cn/percona/release/$releasever/RPMS/$basearch- MariaDB Galera Cluster：
參考倉庫：
https://mirrors.tuna.tsinghua.edu.cn/mariadb/mariadb-5.5.X/yum/centos7-amd64/註意：兩者都需要至少三個節點，不能安裝mysql server 或 mariadb-serverPXC 原理
PXC最常使用如下4個埠號：
• 3306：資料庫對外服務的埠號
• 4444：請求SST的埠號
• 4567：組成員之間進行溝通的埠號
• 4568：用於傳輸IST的埠號PXC中涉及到的重要概念和核心參數：
- 集群中節點的數量：整個集群中節點數量應該控制在最少3個、最多8個的範圍內。最少3個節點是為了防止出現腦裂現象，因為只有在2個節點下才會出現此現象。腦裂現象的標誌就是輸入任何命令，返回的結果都是unknown command。節點在集群中，會因新節點的加入或故障、同步失效等原因發生狀態的切換。
- 節點狀態的變化階段：
• open：節點啟動成功，嘗試連接到集群時的狀態
• primary：節點已處於集群中，在新節點加入並選取donor進行數據同步時的狀態
• joiner：節點處於等待接收同步文件時的狀態
• joined：節點完成數據同步工作，嘗試保持和集群進度一致時的狀態
• synced：節點正常提供服務時的狀態，表示已經同步完成並和集群進度保持一致
• donor：節點處於為新加入的節點提供全量數據時的狀態 備註：donor節點就是數據的貢獻者，如果一個新節點加入集群，此時又需要大量數據的SST數據傳輸，就有可能因此而拖垮整個集群的性能，所以在生產環境中，如果數據量較小，還可以使用SST全量數據傳輸，但如果數據量很大就不建議使用這種方式，可以考慮先建立主從關係，然後再加入集群。- 節點的數據傳輸方式：
• SST：State Snapshot Transfer，全量數據傳輸
• IST：Incremental State Transfer，增量數據傳輸 SST數據傳輸有xtrabackup、mysqldump和rsync三種方式，而增量數據傳輸就只有一種方式xtrabackup，但生產環境中一般數據量較小時，可以使用SST全量數據傳輸，但也只使用xtrabackup方法。- GCache模塊：
在PXC中一個特別重要的模塊，它的核心功能就是為每個節點緩存當前最新的寫集。如果有新節點加入進來，就可以把新數據的增量傳遞給新節點，而不需要再使用SST傳輸方式，這樣可以讓節點更快地加入集群中- 涉及如下參數：
• gcache.size：緩存寫集增量信息的大小，它的預設大小是128MB，通過wsrep_provider_options參數設置，建議調整為2GB~4GB範圍，足夠的空間便於緩存更多的增量信息。
• gcache.mem_size：GCache中記憶體緩存的大小，適度調大可以提高整個集群的性能
• gcache.page_size：如果記憶體不夠用（GCache不足），就直接將寫集寫入磁碟文件中實戰案例：Percona XtraDB Cluster(PXC 5.7）
環境準備
四台主機：
pxc1:192.168.39.7 pxc1:192.168.39.27 pxc1:192.168.39.37 pxc4:192.168.39.47OS版本
關閉防火牆和SELinux，保證時間同步[root@pxc1 ~]#cat /etc/redhat-release CentOS Linux release 7.6.1810 (Core)
註意：如果已經安裝MySQL，必須卸載- 安裝 Percona XtraDB Cluster 5.7
- 配置yum源
[root@pxc1 ~]#vim /etc/yum.repos.d/percona_pxc.repo
[percona]
name=percona_repo
baseurl=https://mirrors.tuna.tsinghua.edu.cn/percona/release/$releasever/RPMS/$basearch
enabled=1
gpgcheck=0- 其他三台虛擬機也配置yum源
scp /etc/yum.repos.d/percona_pxc.repo 192.168.39.27:/etc/yum.repos.d/
scp /etc/yum.repos.d/percona_pxc.repo 192.168.39.37:/etc/yum.repos.d/
scp /etc/yum.repos.d/percona_pxc.repo 192.168.39.47:/etc/yum.repos.d/- 在三個節點都安裝好PXC 5.7
[root@pxc1 ~]#yum install Percona-XtraDB-Cluster-57 -y
[root@pxc2 ~]#yum install Percona-XtraDB-Cluster-57 -y
[root@pxc3 ~]#yum install Percona-XtraDB-Cluster-57 -y
[root@pxc4 ~]#yum install Percona-XtraDB-Cluster-57 -y- 在各個節點上分別配置mysql及集群配置文件
/etc/my.cnf為主配置文件，當前版本中，其餘的配置文件都放在/etc/percona-xtradb-cluster.conf.d目錄里，包括mysqld.cnf，mysqld_safe.cnf，wsrep.cnf 三個文件#主配置文件不需要修改
[root@pxc1 ~]#cat /etc/my.cnf
#
# The Percona XtraDB Cluster 5.7 configuration file.
#
#
# * IMPORTANT: Additional settings that can override those from this file!
# The files must end with '.cnf', otherwise they'll be ignored.
# Please make any edits and changes to the appropriate sectional files
# included below.
#
!includedir /etc/my.cnf.d/
!includedir /etc/percona-xtradb-cluster.conf.d/
[root@pxc1 ~]#ls /etc/percona-xtradb-cluster.conf.d/ # 查看一下三個文件
mysqld.cnf mysqld_safe.cnf wsrep.cnf
#下麵配置文件不需要修改
[root@pxc1 ~]#cat /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=1 # 建議各個節點不同
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 # 建議啟用，非必須項
log_slave_updates
expire_logs_days=7
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
#下麵配置文件不需要修改
[root@pxc1 ~]#cat /etc/percona-xtradb-cluster.conf.d/mysqld_safe.cnf
#
# The Percona Server 5.7 configuration file.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
[mysqld_safe]
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/lib/mysql/mysql.sock
nice = 0
#PXC的配置文件必須修改
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://10.0.0.7,10.0.0.17,10.0.0.27 #三個節點的IP
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=10.0.0.7 #各個節點，指定自已的IP
wsrep_cluster_name=pxc-cluster # 集群名稱
wsrep_node_name=pxc-cluster-node-1 #各個節點，指定自已節點名稱
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:centos7" #取消本行註釋，可以改一個自己的密碼
# 根據以上修改信息所有主機都修改
[root@pxc2 ~]#vim /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[root@pxc3 ~]#vim /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[root@pxc1 ~]#grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf # 通過這個命令查看配置文件
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://192.168.39.7,192.168.39.27,192.168.39.37
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=192.168.39.7
wsrep_cluster_name=pxc-cluster
wsrep_node_name=pxc-cluster-node-1
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:centos7"註意：儘管Galera Cluster不再需要通過binlog的形式進行同步，但還是建議在配置文件中開啟二進位日誌功能，原因是後期如果有新節點需要加入，老節點通過SST全量傳輸的方式向新節點傳輸數據，很可能會拖垮集群性能，所以讓新節點先通過binlog方式完成同步後再加入集群會是一種更好的選擇- 配置文件各項配置意義
[root@pxc1 ~]#ss -ntul
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
udp UNCONN 0 0 192.168.122.1:53 *:*
udp UNCONN 0 0 *%virbr0:67 *:*
udp UNCONN 0 0 *:111 *:*
udp UNCONN 0 0 *:5353 *:*
udp UNCONN 0 0 *:58153 *:*
udp UNCONN 0 0 *:812 *:*
udp UNCONN 0 0 :::111 :::*
udp UNCONN 0 0 :::812 :::*
tcp LISTEN 0 128 *:111 *:*
tcp LISTEN 0 128 *:6000 *:*
tcp LISTEN 0 5 192.168.122.1:53 *:*
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 128 127.0.0.1:631 *:*
tcp LISTEN 0 128 127.0.0.1:6010 *:*
tcp LISTEN 0 128 :::111 :::*
tcp LISTEN 0 128 :::6000 :::*
tcp LISTEN 0 128 :::22 :::*
tcp LISTEN 0 128 ::1:631 :::*
tcp LISTEN 0 128 ::1:6010 :::*
#啟動第一人節點（第一個節點啟動和別的節點啟動都不一樣）屬於創建集群的伺服器現在階段可以理解為主伺服器，但是集群做完之後就沒有主從之分了都是主
[root@pxc1 ~]#systemctl start [email protected]
[root@pxc1 ~]#ss -ntul # 以下兩個埠啟動起來就行了 （3306、4567）
。。。。。。。。。。。。。。。。。。。。。。。
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
udp UNCONN 0 0 192.168.122.1:53 *:*
udp UNCONN 0 0 *%virbr0:67 *:*
udp UNCONN 0 0 *:111 *:*
udp UNCONN 0 0 *:5353 *:*
udp UNCONN 0 0 *:58153 *:*
udp UNCONN 0 0 *:812 *:*
udp UNCONN 0 0 :::111 :::*
udp UNCONN 0 0 :::812 :::*
tcp LISTEN 0 128 *:111 *:*
tcp LISTEN 0 128 *:6000 *:*
tcp LISTEN 0 5 192.168.122.1:53 *:*
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 128 *:4567 *:*
tcp LISTEN 0 128 127.0.0.1:631 *:*
tcp LISTEN 0 128 127.0.0.1:6010 *:*
tcp LISTEN 0 80 :::3306 :::*
tcp LISTEN 0 128 :::111 :::*
tcp LISTEN 0 128 :::6000 :::*
tcp LISTEN 0 128 :::22 :::*
tcp LISTEN 0 128 ::1:631 :::*
tcp LISTEN 0 128 ::1:6010 :::* - 找到MySQL的臨時密碼，第一次登錄要修改要不執行不了管理操作。
[root@centos7 ~]#grep "password" /var/log/mysqld.log
2019-12-03T06:13:39.187929Z 1 [Note] A temporary password is generated for root@localhost: a>#;L(Sm4Ln:
[root@centos7 ~]#mysql -uroot -p'a>#;L(Sm4Ln:' # 需要加引號引起來
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: 5.7.27-30-57-log
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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; # 執行查看庫操作提示必須重置密碼
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement. # 在執行此語句之前，必須使用ALTER USER語句重置密碼.
mysql> alter user root@'localhost' identified by 'magedu'; # 修改密碼（其他節點不用修改加入集群以後會自動同步密碼）
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
[root@centos7 ~]#mysql -uroot -pmagedu # 修改以後重新登錄
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 12
Server version: 5.7.27-30-57-log Percona XtraDB Cluster (GPL), Release rel30, Revision 64987d4, WSREP version 31.39, wsrep_31.39
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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>- 查看變數
# 查看寫集複製相關變數
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://192.168.39.7,192.168.39.27,192.168.39.37
*************************** 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_node_address
Value: 192.168.39.7
*************************** 22. row ***************************
Variable_name: wsrep_node_incoming_address
Value: AUTO
*************************** 23. row ***************************
Variable_name: wsrep_node_name
Value: pxc-cluster-node-1
*************************** 24. row ***************************
Variable_name: wsrep_notify_cmd
Value:
*************************** 25. row ***************************
Variable_name: wsrep_on
Value: ON
*************************** 26. row ***************************
Variable_name: wsrep_preordered
Value: OFF
*************************** 27. row ***************************
Variable_name: wsrep_provider
Value: /usr/lib64/galera3/libgalera_smm.so
*************************** 28. row ***************************
Variable_name: wsrep_provider_options
Value: base_dir = /var/lib/mysql/; base_host = 192.168.39.7; 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;
*************************** 29. row ***************************
Variable_name: wsrep_recover
Value: OFF
*************************** 30. row ***************************
Variable_name: wsrep_reject_queries
Value: NONE
*************************** 31. row ***************************
Variable_name: wsrep_replicate_myisam
Value: OFF
*************************** 32. row ***************************
Variable_name: wsrep_restart_slave
Value: OFF
*************************** 33. row ***************************
Variable_name: wsrep_retry_autocommit
Value: 1
*************************** 34. row ***************************
Variable_name: wsrep_slave_FK_checks
Value: ON
*************************** 35. row ***************************
Variable_name: wsrep_slave_UK_checks
Value: OFF
*************************** 36. row ***************************
Variable_name: wsrep_slave_threads
Value: 8
*************************** 37. row ***************************
Variable_name: wsrep_sst_auth
Value: ********
*************************** 38. row ***************************
Variable_name: wsrep_sst_donor
Value:
*************************** 39. row ***************************
Variable_name: wsrep_sst_donor_rejects_queries
Value: OFF
*************************** 40. row ***************************
Variable_name: wsrep_sst_method
Value: xtrabackup-v2
*************************** 41. row ***************************
Variable_name: wsrep_sst_receive_address
Value: AUTO
*************************** 42. row ***************************
Variable_name: wsrep_start_position
Value: 00000000-0000-0000-0000-000000000000:-1
*************************** 43. row ***************************
Variable_name: wsrep_sync_wait
Value: 0
43 rows in set (0.01 sec)
# 查看相關狀態變數
mysql> SHOW STATUS LIKE 'wsrep%'\G
*************************** 1. row ***************************
Variable_name: wsrep_local_state_uuid
Value: 10c3398e-1594-11ea-9f84-c2cae1c33555
*************************** 2. row ***************************
Variable_name: wsrep_protocol_version
Value: 9
*************************** 3. row ***************************
Variable_name: wsrep_last_applied
Value: 1
*************************** 4. row ***************************
Variable_name: wsrep_last_committed
Value: 1
*************************** 5. row ***************************
Variable_name: wsrep_replicated
Value: 1
*************************** 6. row ***************************
Variable_name: wsrep_replicated_bytes
Value: 232
*************************** 7. row ***************************
Variable_name: wsrep_repl_keys
Value: 1
*************************** 8. row ***************************
Variable_name: wsrep_repl_keys_bytes
Value: 32
*************************** 9. row ***************************
Variable_name: wsrep_repl_data_bytes
Value: 133
*************************** 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: 154
*************************** 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_cert_deps_distance
Value: 1.000000
*************************** 34. row ***************************
Variable_name: wsrep_apply_oooe
Value: 0.000000
*************************** 35. row ***************************
Variable_name: wsrep_apply_oool
Value: 0.000000
*************************** 36. row ***************************
Variable_name: wsrep_apply_window
Value: 1.000000
*************************** 37. row ***************************
Variable_name: wsrep_commit_oooe
Value: 0.000000
*************************** 38. row ***************************
Variable_name: wsrep_commit_oool
Value: 0.000000
*************************** 39. row ***************************
Variable_name: wsrep_commit_window
Value: 1.000000
*************************** 40. row ***************************
Variable_name: wsrep_local_state
Value: 4
*************************** 41. row ***************************
Variable_name: wsrep_local_state_comment
Value: Synced
*************************** 42. row ***************************
Variable_name: wsrep_cert_index_size
Value: 1
*************************** 43. row ***************************
Variable_name: wsrep_cert_bucket_count
Value: 22
*************************** 44. row ***************************
Variable_name: wsrep_gcache_pool_size
Value: 1592
*************************** 45. row ***************************
Variable_name: wsrep_causal_reads
Value: 0
*************************** 46. row ***************************
Variable_name: wsrep_cert_interval
Value: 0.000000
*************************** 47. row ***************************
Variable_name: wsrep_open_transactions
Value: 0
*************************** 48. row ***************************
Variable_name: wsrep_open_connections
Value: 0
*************************** 49. row ***************************
Variable_name: wsrep_ist_receive_status
Value:
*************************** 50. row ***************************
Variable_name: wsrep_ist_receive_seqno_start
Value: 0
*************************** 51. row ***************************
Variable_name: wsrep_ist_receive_seqno_current
Value: 0
*************************** 52. row ***************************
Variable_name: wsrep_ist_receive_seqno_end
Value: 0
*************************** 53. row ***************************
Variable_name: wsrep_incoming_addresses
Value: 192.168.39.7:3306
*************************** 54. row ***************************
Variable_name: wsrep_cluster_weight
Value: 1
*************************** 55. row ***************************
Variable_name: wsrep_desync_count
Value: 0
*************************** 56. row ***************************
Variable_name: wsrep_evs_delayed
Value:
*************************** 57. row ***************************
Variable_name: wsrep_evs_evict_list
Value:
*************************** 58. row ***************************
Variable_name: wsrep_evs_repl_latency
Value: 0/0/0/0/0
*************************** 59. row ***************************
Variable_name: wsrep_evs_state
Value: OPERATIONAL
*************************** 60. row ***************************
Variable_name: wsrep_gcomm_uuid
Value: 10c2c674-1594-11ea-83fc-6e0df986585c
*************************** 61. row ***************************
Variable_name: wsrep_cluster_conf_id
Value: 1
*************************** 62. row ***************************
Variable_name: wsrep_cluster_size
Value: 1
*************************** 63. row ***************************
Variable_name: wsrep_cluster_state_uuid
Value: 10c3398e-1594-11ea-9f84-c2cae1c33555
*************************** 64. row ***************************
Variable_name: wsrep_cluster_status
Value: Primary
*************************** 65. row ***************************
Variable_name: wsrep_connected
Value: ON
*************************** 66. row ***************************
Variable_name: wsrep_local_bf_aborts
Value: 0
*************************** 67. row ***************************
Variable_name: wsrep_local_index
Value: 0
*************************** 68. row ***************************
Variable_name: wsrep_provider_name
Value: Galera
*************************** 69. row ***************************
Variable_name: wsrep_provider_vendor
Value: Codership Oy <[email protected]>
*************************** 70. row ***************************
Variable_name: wsrep_provider_version
Value: 3.39(rb3295e6)
*************************** 71. row ***************************
Variable_name: wsrep_ready
Value: ON
71 rows in set (0.00 sec)
#重點內容
mysql> SHOW STATUS like 'wsrep%';
+----------------------------------+--------------------------------------+
| Variable_name | Value |
+----------------------------------+--------------------------------------+
| wsrep_local_state_uuid | 10c3398e-1594-11ea-9f84-c2cae1c33555 |
| wsrep_protocol_version | 9 |
| wsrep_last_applied | 1 |
| wsrep_last_committed | 1 |
| wsrep_replicated | 1 |
| wsrep_replicated_bytes | 232 |
| wsrep_repl_keys | 1 |
| wsrep_repl_keys_bytes | 32 |
| wsrep_repl_data_bytes | 133 |
| wsrep_repl_other_bytes | 0 |
| wsrep_received | 2 |
| wsrep_received_bytes | 154 |
| wsrep_local_commits | 0 |
| wsrep_local_cert_failures | 0 |
| wsrep_local_replays | 0 |
| wsrep_local_send_queue | 0 |
| wsrep_local_send_queue_max | 1 |
| wsrep_local_send_queue_min | 0 |
| wsrep_local_send_queue_avg | 0.000000 |
| wsrep_local_recv_queue | 0 |
| wsrep_local_recv_queue_max | 2 |
| wsrep_local_recv_queue_min | 0 |
| wsrep_local_recv_queue_avg | 0.500000 |
| wsrep_local_cached_downto | 1 |
| wsrep_flow_control_paused_ns | 0 |
| wsrep_flow_control_paused | 0.000000 |
| wsrep_flow_control_sent | 0 |
| wsrep_flow_control_recv | 0 |
| wsrep_flow_control_interval | [ 100, 100 ] |
| wsrep_flow_control_interval_low | 100 |
| wsrep_flow_control_interval_high | 100 |
| wsrep_flow_control_status | OFF |
| wsrep_cert_deps_distance | 1.000000 |
| wsrep_apply_oooe | 0.000000 |
| wsrep_apply_oool | 0.000000 |
| wsrep_apply_window | 1.000000 |
| wsrep_commit_oooe | 0.000000 |
| wsrep_commit_oool | 0.000000 |
| wsrep_commit_window | 1.000000 |
| wsrep_local_state | 4 |
| wsrep_local_state_comment | Synced |
| wsrep_cert_index_size | 1 |
| wsrep_cert_bucket_count | 22 |
| wsrep_gcache_pool_size | 1592 |
| wsrep_causal_reads | 0 |
| wsrep_cert_interval | 0.000000 |
| wsrep_open_transactions | 0 |
| wsrep_open_connections | 0 |
| wsrep_ist_receive_status | |
| wsrep_ist_receive_seqno_start | 0 |
| wsrep_ist_receive_seqno_current | 0 |
| wsrep_ist_receive_seqno_end | 0 |
| wsrep_incoming_addresses | 192.168.39.7:3306 |
| wsrep_cluster_weight | 1 |
| 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 | 10c2c674-1594-11ea-83fc-6e0df986585c |
| wsrep_cluster_conf_id | 1 |
| wsrep_cluster_size | 1 |
| wsrep_cluster_state_uuid | 10c3398e-1594-11ea-9f84-c2cae1c33555 |
| wsrep_cluster_status | Primary |
| wsrep_connected | ON |
| wsrep_local_bf_aborts | 0 |
| wsrep_local_index | 0 |
| wsrep_provider_name | Galera |
| wsrep_provider_vendor | Codership Oy <[email protected]> |
| wsrep_provider_version | 3.39(rb3295e6) |
| wsrep_ready | ON |
+----------------------------------+--------------------------------------+
71 rows in set (0.00 sec)說明：
wsrep_cluster_size表示，該Galera集群中只有一個節點
wsrep_local_state_comment 狀態為Synced(4)，表示數據已同步完成(因為是第一個引導節點，無數據需要同步)。 如果狀態是Joiner, 意味著 SST 沒有完成. 只有所有節點狀態是Synced，才可以加新節點
wsrep_cluster_status為Primary，且已經完全連接並準備好啟動PXC集群中其它所有節點
- 啟動PXC集群中其它所有節點
# 啟動前在第一個節點上創建一個授權賬戶（要不然可能別的節點沒有授權資料庫會起不來）
mysql> GRANT RELOAD, LOCK TABLES, PROCESS, REPLICATION CLIENT ON *.* TO 'sstuser'@'localhost' identified by 'centos7'; # 這裡授權的密碼必須和配置文件里設置的密碼對應，所有伺服器都要一樣。
Query OK, 0 rows affected, 1 warning (0.00 sec)
[root@pxc2 etc]#ss -ntl # 啟動前埠情況
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:111 *:*
LISTEN 0 128 *:6000 *:*
LISTEN 0 5 192.168.122.1:53 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 128 127.0.0.1:631 *:*
LISTEN 0 128 127.0.0.1:6010 *:*
LISTEN 0 128 :::111 :::*
LISTEN 0 128 :::6000 :::*
LISTEN 0 128 :::22 :::*
LISTEN 0 128 ::1:631 :::*
LISTEN 0 128 ::1:6010 :::*
[root@pxc2 etc]#systemctl start mysql # 啟動資料庫
[root@pxc2 etc]#ss -ntl # 啟動後 3306、4567 埠都出現了
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:111 *:*
LISTEN 0 128 *:6000 *:*
LISTEN 0 5 192.168.122.1:53 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 128 *:4567 *:*
LISTEN 0 128 127.0.0.1:631 *:*
LISTEN 0 128 127.0.0.1:6010 *:*
LISTEN 0 128 127.0.0.1:6011 *:*
LISTEN 0 80 :::3306 :::*
LISTEN 0 128 :::111 :::*
LISTEN 0 128 :::6000 :::*
LISTEN 0 128 :::22 :::*
LISTEN 0 128 ::1:631 :::*
LISTEN 0 128 ::1:6010 :::*
LISTEN 0 128 ::1:6011 :::*
[root@pxc2 etc]#mysql -uroot -pmagedu # 登錄資料庫
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: 5.7.27-30-57-log Percona XtraDB Cluster (GPL), Release rel30, Revision 64987d4, WSREP version 31.39, wsrep_31.39
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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>
# 另一個節點一樣啟動
[root@pxc3 etc]#systemctl start mysql # 啟動資料庫
[root@pxc3 ~]#mysql -uroot -pmagedu
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: 5.7.27-30-57-log Percona XtraDB Cluster (GPL), Release rel30, Revision 64987d4, WSREP version 31.39, wsrep_31.39
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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>
- 查看集群狀態，驗證集群是否成功
# 在任意節點，查看集群狀態
mysql> SHOW VARIABLES LIKE 'wsrep_node_name';
+-----------------+--------------------+
| Variable_name | Value |
+-----------------+--------------------+
| wsrep_node_name | pxc-cluster-node-1 |
+-----------------+--------------------+
1 row in set (0.00 sec)
mysql> show variables like 'wsrep_node_address';
+--------------------+--------------+
| Variable_name | Value |
+--------------------+--------------+
| wsrep_node_address | 192.168.39.7 |
+--------------------+--------------+
1 row in set (0.01 sec)
mysql> show variables like 'wsrep_on';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wsrep_on | ON |
+---------------+-------+
1 row in set (0.00 sec)
mysql> show status like 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 3 |
+--------------------+-------+
1 row in set (0.00 sec)
# 在任意節點創建資料庫測試（pxc2）
mysql> SHOW VARIABLES LIKE 'wsrep_node_address';
+--------------------+---------------+
| Variable_name | Value |
+--------------------+---------------+
| wsrep_node_address | 192.168.39.27 |
+--------------------+---------------+
1 row in set (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
mysql> create database db1;
Query OK, 1 row affected (0.01 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
# 在pxc1上查看
mysql> SHOW VARIABLES LIKE 'wsrep_node_address';
+--------------------+--------------+
| Variable_name | Value |
+--------------------+--------------+
| wsrep_node_address | 192.168.39.7 |
+--------------------+--------------+
1 row in set (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
# 在pxc2上查看
mysql> SHOW VARIABLES LIKE 'wsrep_node_address';
+--------------------+---------------+
| Variable_name | Value |
+--------------------+---------------+
| wsrep_node_address | 192.168.39.37 |
+--------------------+---------------+
1 row in set (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
# 兩個節點都可以看到同步成功- 測試是否有衝突問題
#利用Xshell軟體，同時在三個節點資料庫，在其中一個節點成功
mysql> create database db2; # 只有一個節點會成功其他節點報錯不創建
Query OK, 1 row affected (0.00 sec)
mysql> create database db2;
ERROR 1007 (HY000): Can't create database 'db2'; database exists
mysql> create database db2;
ERROR 1007 (HY000): Can't create database 'db2'; database exists- PXC缺點（同時寫入數據性能會有影響）
# 使用一個命令迴圈創建10w條記錄
mysql> create table test (id int auto_increment primary key,name char(10));
delimiter ;
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> delimiter $$
mysql>
mysql> create procedure proc_test()
-> begin
-> declare i int;
-> set i = 1;
-> while i < 100000
-> do insert into test(name) values (concat('wang',i));
-> set i = i +1;
-> end while;
-> end$$
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> delimiter ;
mysql> call proc_test();
Query OK, 1 row affected (3 min 39.51 sec) # 用了39s接近40s時間才添加完成
# 使用事務方式添加記錄還是很快的
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> call proc_test();
Query OK, 1 row affected (2.44 sec)
mysql> commit;
Query OK, 0 rows affected (0.25 sec)
- 添加記錄的話每個節點添加id變化
# 每個節點添加記錄可重覆。（是自動增長的）
mysql> insert t1(name)values('mage');
Query OK, 1 row affected (0.01 sec)
mysql> select * from t1;
+----+-------+
| id | name |
+----+-------+
| 1 | mage |
| 4 | magea |
| 7 | mageb |
| 10 | mage |
+----+-------+
4 rows in set (0.00 sec)
# 2 節點添加
mysql> insert t1(name)values('mage');
Query OK, 1 row affected (0.00 sec)
mysql> insert t1(name)values('mage');
Query OK, 1 row affected (0.00 sec)
mysql> insert t1(name)values('mage');
Query OK, 1 row affected (0.00 sec)
mysql> select * from t1;
+----+-------+
| id | name |
+----+-------+
| 1 | mage |
| 4 | magea |
| 7 | mageb |
| 10 | mage |
| 11 | mage |
| 14 | mage |
| 17 | mage |
+----+-------+
7 rows in set (0.00 sec)在PXC集群中加入節點
一個節點加入到Galera集群有兩種情況：新節點加入集群、暫時離組的成員再次加入集群
1）新節點加入Galera集群
新節點加入集群時，需要從當前集群中選擇一個Donor節點來同步數據，也就是所謂state_snapshot_tranfer(SST)過程。SST同步數據的方式由選項wsrep_sst_method決定，一般選擇的是xtrabackup。
必須註意，新節點加入Galera時，會刪除新節點上所有已有數據，再通過xtrabackup(假設使用的是該方式)從Donor處完整備份所有數據進行恢復。所以，如果數據量很大，新節點加入過程會很慢。而且，在一個新節點成為Synced狀態之前，不要同時加入其它新節點，否則很容易將集群壓垮。如果是這種情況，可以考慮使用wsrep_sst_method=rsync來做增量同步，既然是增量同步，最好保證新節點上已經有一部分數據基礎，否則和全量同步沒什麼區別，且這樣會對Donor節點加上全局readonly鎖。
2）舊節點加入Galera集群
如果舊節點加入Galera集群，說明這個節點在之前已經在Galera集群中呆過，有一部分數據基礎，缺少的只是它離開集群時的數據。這時加入集群時，會採用IST(incremental snapshot transfer)傳輸機制，即使用增量傳輸。# 同樣先配置yum源
# 在安裝資料庫
[root@pxc4 ~]#yum install Percona-XtraDB-Cluster-57 -y
# 修改配置文件
[root@pxc4 ~]#grep -Ev "^#|^$" /etc/percona-xtradb-cluster.conf.d/wsrep.cnf
[mysqld]
wsrep_provider=/usr/lib64/galera3/libgalera_smm.so
wsrep_cluster_address=gcomm://192.168.39.7,192.168.39.27,192.168.39.37,192.168.39.47 # 這一行添加上新節點的ip（雖然其他節點配置文件不添加也可以，但是最好都加上，比如說伺服器依次關機到新添加的節點（新添加的節點留為最後的引導伺服器），但是下次開機別的節點會找不到新添加的伺服器，資料庫就起不來了）
binlog_format=ROW
default_storage_engine=InnoDB
wsrep_slave_threads= 8
wsrep_log_conflicts
innodb_autoinc_lock_mode=2
wsrep_node_address=192.168.39.47
wsrep_cluster_name=pxc-cluster
wsrep_node_name=pxc-cluster-node-4
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
wsrep_sst_auth="sstuser:centos7"
# 查看連接數以變為4個
mysql> show status like 'wsrep_cluster_size'\G
*************************** 1. row ***************************
Variable_name: wsrep_cluster_size
Value: 4
1 row in set (0.00 sec)在PXC集群中修複故障節點
- 在其他節點停止服務
[root@pxc2 ~]#systemctl stop mysql
[root@pxc2 ~]#systemctl status mysql
● mysql.service - Percona XtraDB Cluster
Loaded: loaded (/usr/lib/systemd/system/mysql.service; enabled; vendor preset: disabled)
Active: inactive (dead) since Tue 2019-12-03 16:52:51 CST; 3min 21s ago
Process: 29259 ExecStopPost=/usr/bin/mysql-systemd stop-post (code=exited, status=0/SUCCESS)
Process: 29221 ExecStop=/usr/bin/mysql-systemd stop (code=exited, status=0/SUCCESS)
Process: 26928 ExecStartPost=/usr/bin/mysql-systemd start-post $MAINPID (code=exited, status=0/SUCCESS)
Process: 26925 ExecStart=/usr/bin/mysqld_safe --basedir=/usr (code=exited, status=0/SUCCESS)
Process: 26853 ExecStartPre=/usr/bin/mysql-systemd start-pre (code=exited, status=0/SUCCESS)
Main PID: 26925 (code=exited, status=0/SUCCESS)
Dec 03 15:12:54 pxc2 mysqld_safe[26925]: 2019-12-03T07:12:54.344288Z mysqld_safe Assigning 00000000-0000-0000-0000-000000000000:-1 to wsrep_start_position
Dec 03 15:12:56 pxc2 mysql-systemd[26928]: State transfer in progress, setting sleep higher
Dec 03 15:13:16 pxc2 mysql-systemd[26928]: SUCCESS!
Dec 03 15:13:16 pxc2 systemd[1]: Started Percona XtraDB Cluster.
Dec 03 16:52:39 centos7.localdomain systemd[1]: Stopping Percona XtraDB Cluster...
Dec 03 16:52:39 centos7.localdomain mysql-systemd[29221]: SUCCESS! Stopping Percona XtraDB Cluster......
Dec 03 16:52:51 centos7.localdomain mysqld_safe[26925]: 2019-12-03T08:52:51.720383Z mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
Dec 03 16:52:51 centos7.localdomain mysql-systemd[29259]: WARNING: mysql pid file /var/run/mysqld/mysqld.pid empty or not readable
Dec 03 16:52:51 centos7.localdomain mysql-systemd[29259]: WARNING: mysql may be already dead
Dec 03 16:52:51 centos7.localdomain systemd[1]: Stopped Percona XtraDB Cluster.- 在其它任意節點查看wsrep_cluster_size變數
[root@centos7 ~]#mysql -uroot -pmagedu
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 21
Server version: 5.7.27-30-57-log Percona XtraDB Cluster (GPL), Release rel30, Revision 64987d4, WSREP version 31.39, wsrep_31.39
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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 status like 'wsrep_cluster_size'\G
*************************** 1. row ***************************
Variable_name: wsrep_cluster_size
Value: 3 # 少了一個節點
1 row in set (0.00 sec)- 添加一個資料庫查看同步情況
mysql> create database db4;
Query OK, 1 row affected (0.01 sec)
#在其它任意節點可看到數據已同步
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| db2 |
| db3 |
| db4 |
| mysql |
| performance_schema |
| sys |
+--------------------+
8 rows in set (0.00 sec)
# 其他節點正常同步- 恢復服務，數據同步
[root@pxc2 ~]#systemctl start mysql
[root@pxc2 ~]#mysql -uroot -pmagedu
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: 5.7.27-30-57-log Percona XtraDB Cluster (GPL), Release rel30, Revision 64987d4, WSREP version 31.39, wsrep_31.39
Copyright (c) 2009-2019 Percona LLC and/or its affiliates
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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 |
| db1 |
| db2 |
| db3 |
| db4 |
| mysql |
| performance_schema |
| sys |
+--------------------+
8 rows in set (0.00 sec)
# 恢復服務之後數據還是能同步的
mysql> SHOW STATUS LIKE 'wsrep_cluster_size';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| wsrep_cluster_size | 4 |
+--------------------+-------+
1 row in set (0.00 sec)實現MariaDB Galera Cluster
#在三個節點上都實現
[root@centos8 ~]
