- Overview
- Galera Cluster
- Percona XtraDB Cluster
- MySQL Group Replication
- MySQL InnoDB Cluster
- Similarities
- Similar - Use Cases
- Similar Limitation
- Differences GR & Galera
- Group Communication System 组通信系统
- Binlogs & Gcache
- Node Provisioning 节点配置
- GTID vs. Seqno
- Partition Handling
- Full Solution or Plugin
- Flow Control 流控制
- WAN Support
- OS Support
- Schema Changes - DDL
- Differences PXC & Galera
- PXC Strict Mode
- ProxySQL 集成
- 性能提升
- Limitations
- Known Issues
- Galera Cluster/PXC Issues
- Group Replication Issues
- 分区容忍问题，不能防止脑裂
- 减少冲突
- 稳定性
- 可用性
- Q & A
- Performance Tests
Overview
Galera Cluster
- 由 Coder<!---->ship 开发 官网
- 包含在MariaDB，在Percona、MySQL 都可以使用
Galera Cluster 是一个基于 InnoDB 多主的同步复制，可以读写任何节点，即使失去任何一个节点也不影响业务中断，而且无需复杂的 failover 操作。
Percona XtraDB Cluster
- 由 Percona 开发，在 Galera 基础打 Patch 官网
- 自 2012 年 4 月可用
- 附加的特性
- PFS 扩展支持
- SST/XtraBackup 方式的改变
- PXC Strict mode *
- ProxySQL 集成 *
- 提升性能 *
MySQL Group Replication
- 由 Oracle 官方开发
- 2016 年 12 月 MySQL 5.7.17 发布 GA
- MySQL InnoDB Cluster 整体解决方案
MySQL Group Replication 是一个 MySQL Server Plugin，提供分布式状态机复制与 Server 强大协调，当在一个 Group Replication 时，Server 将自动协调，每个节点都可以自动处理更新，自动检测，有一个 membership service 维护一个 view，记录组内 记录可见成员在某个时间点一致性和高可用性的，当任何一个成加入或离开，view 就会相应的更新
MySQL InnoDB Cluster
Similarities
- MySQL/MariaDB
- 复制方法
- 所有节点都有全部的数据 - 读仅发生在当前本地节点
- 都需要 InnoDB/XtraDB 引擎
- 都支持 多主的拓扑 (Active-active multi-master Topology)
- 写多主节点
- 不需要复杂的 Failover 操作
- 节点管理，加入和离开都是完全自动处理的
- 执行和写都是按全局的顺序进行的
- 数据一致性
- 乐观锁 / 最早提交的先赢
- Quorum - 防止脑裂
Similar - Use Cases
- 严格的持久化环境
- 同时定入多个节点，保证数据一致性
- 减少故障转移时间 (Reduce failover time)
Similar Limitation
- 大事务或长事务
- 很大的可能失败
- 大事务导致在有效事务
- 热点，多个节点更新同一行数据
- 只有一个节点写，是最好的解决方案
Differences GR & Galera
- Group Communication System 组通信系统
- Binlogs & Gcache
- Node Provisioning 节点配置
- GTID vs Seqno
- Partition Handling 分区控制
- Full Solution or Plugin
- Flow Control 流控制
- WAN Support
- OS Support
- Schema Changes DDL
Group Communication System 组通信系统
- Galera
- 标志的单环顺序 Totem Single-ring Ordering
- 所有节点都必须有 ACK 消息
- MySQL Group Replication
- 基于 Paxos
- Paxos 只要求大多数 ACK 消息
Binlogs & Gcache
- Galera Cluster/PXC
- uses binlog row events
- but does not require binary logging
- writes events to Gcache (con gurable size)
- MySQL Group Replication
- requires binary logging
Node Provisioning 节点配置
- Galera Cluster/PXC
- has State Snapshot Transfer (SST) 全量同步
- Percona XtraBackup (Recommended)
- rsync
- mysqldump
- incremental State Transfer (IST) using GCache 增量同步
- has State Snapshot Transfer (SST) 全量同步
- MySQL Group Replication
- 没有自动全量同步，除非保留所有 Binlog
- 用于同步的异步复制通道
GTID vs. Seqno
- Galera Cluster/PXC
- has a seqno which is a incrementing number
- MySQL Group Replication
- 依赖 MySQL GTID
- writes to a cluster create GTID events on the GR Cluster UUID
Partition Handling
- Galera Cluster/PXC
- A partitioned node will refuse reads/writes (con gurable)
- A partitioned node will automatically recover and rejoin
- MySQL Group Replication
- A partitioned node will accept reads
- A partitioned node will accept write requests, but will hang forever
- A partitioned node needs to be manually rejoined to the cluster
Full Solution or Plugin
- Plugin
- Group Replication is a 'Replication Plugin'
- several split brain bugs in current code ( fixes pending!)
- Solution
- Galera Cluster 不处理应用连接
- 与 GR 相比有更强的防止脑裂
- MySQL InnoDB Cluster (w. MySQLRouter)
- Full Solution
- Percona XtraDB Cluster (w. ProxySQL)
- 集成 ProxySQL
- 严格的 mode，防止使用限制
Flow Control 流控制
防止太慢的节点，被落下太远
- Galera Cluster/PXC
- 当一个节点慢到一个限制，阻止所有节点写
- Flow Control 的消息已经发送
- low defaults; Galera: 16(*), PXC: 100
- Tell others to stop writes
- MySQL Group Replication
- 每个节点都有每个成员的统计信息
- 每个独立的节点决定写的阈值
- high default: 25000
- 如果有节点太慢，其他节点放慢写速度
WAN Support
- Galera Cluster/PXC
- 投票权重
- 调节网络通信设置
- 减少分段网络流量
- 仲裁人
- MySQL Group Replication
- 不建议在 WAN 上使用
OS Support
- Galera
- FreeBSD & Linux
- Galera Cluster/PXC
- Linux
- MySQL Group Replication
- Linux, Windows, Solaris, OSX, FreeBSD
Schema Changes - DDL
- Galera Cluster/PXC
- Total Order Isolation
- All writes will be blocked during Writes on other nodes will be terminated
- Workarounds 变通办法
- pt-online-schema-change
- wsrep_osu_method=RSU
- 更多的操作工作
- 并不是所有 DDL 可行
- MySQL Group Replication
- DDL 并不会阻塞写，像平常使用一样
- 仅建议在单主模式下使用 (因为 DDL 并没有冲突检测)
Differences PXC & Galera
- 扩展 PFS 支持
- SST/XtraBackup 方式的改变
- Bug-Fixes
- PXC Strict Mode - PXC 严格的 Mode
- ProxySQL 集成
- 性能提升
PXC Strict Mode
预防实验性或不支持的特性
- 仅支持 InnoDB 的操作
- 预防修改 binlog_format!=ROW
- 需要 Table 有主键
- 禁用不支持的特性
- GET_LOCK,LOCK TABLES,CTAS
- FLUSH TABLES WITH READ LOCK
- tx_isolation=SERIALIZABLE
ProxySQL 集成
ProxySQL 在 PXC 当负载均衡的角色
- proxysql-admin 配置工具
- ProxySQL schedulers
- 健康检查
- 重新配置节点
- PXC 维护模式
- tell load balancer to rebalance load
性能提升
- 可伸缩性 fixs PXC 5.7.17
- 新的默认值
- gcs.fc_limit=100
- evs.send_window=10
- evs.user_send_window=4
Limitations
- Galera Cluster/PXC
- InnoDB/XtraDB Only
- tx_isolation=SERIALIZABLE
- GET_LOCK()
- LOCK TABLES
- SELECT ... FOR UPDATE
- Careful with ALTER TABLE ... IMPORT/EXPORT
- Capped maximum transaction size 最大事务
- XA transactions
- Group Replication
- InnoDB/XtraDB Only
- tx_isolation=SERIALIZABLE
- GET_LOCK()
- LOCK TABLES
- SELECT ... FOR UPDATE
- CarefulwithALTER TABLE ... IMPORT/EXPORT.
- Careful with large transactions
- no support for tables with multi-level foreign key dependencies, can create inconsistencies
Known Issues
Galera Cluster/PXC Issues
- Crashes due to background thread handling trx
processing- mysql-wsrep#306: stored procedure aborts
- mysql-wsrep#305: event scheduler
- mysql-wsrep#304: local scope functions such as CURRENT_USER()
- Various crashes related to DDL
- mysql-wsrep#301:runningSHOW CREATE TABLE in multiple nodes with DDL can cause crash.
- mysql-wsrep#275: Aborting trx leaves behind open tables in cache can cause crash
- Concurrent DDLs using wsrep_OSU_method=RSU crash/inconsistency issues
- mysql-wsrep#283 & mysql-wsrep#282
- Shutdown issues
- mysql-wsrep#303: cleanup during shutdown fails to clear the EXPLICT MDL locks (FTWRL)
- mysql-wsrep#273: Not getting clean shutting down message if we start the server with unknown variable
- mysql-wsrep#279: Trying to access stale binlog handler leads to crash
Group Replication Issues
分区容忍问题，不能防止脑裂
* #84727: partitioned nodes still accept writes: queries hang (~Fixed in 5.7.20)
* #84728: GR failure at start still starts MySQL (~Fixed in 8.0.2)
* #84729: block reads on partitioned nodes
* #84733: not possible to start with super_read_only=1 (Fixed in 8.0.2)
* #84784: Nodes Do Not Reconnect
* #84795: STOP GROUP_REPLICATION sets super_read_only=off
减少冲突
* #84731: mysql client connections get stuck during GR start
稳定性
* #84785: Prevent Large Transactions in Group Replication (~Fixed in 5.7.19)
* #84792: Member using 100% CPU in idle cluster (*)
* #84796: GR Member status is wrong
可用性
* #84674: unresolved hostnames block GR from starting (~Fixed in 5.7.18)
* #84794: cannot kill query that is stuck inside GR
* #84798: Group Replication can use some verbosity in the error log
Q & A
这个看原 PDF 吧。
Performance Tests
原文:大专栏 Percona XtraDB Cluster vs Galera Cluster vs MySQL Group Replication
原文地址：https://www.cnblogs.com/petewell/p/11597859.html
时间： 2024-07-31 21:13:47