基於MySQL和DynamoDB的強一致性分佈式事務實踐

原創

2021-10-11 14:48

方案

優點

缺點

強一致性
無業務侵入

同步阻塞
有限的數據源支持，比如MySQL, ActiveMQ
5.7.7版本前，客戶端退出或者服務宕機事務回滾，服務重啓binlog丟失問題

兩階段提交

強一致性

延遲：同步阻塞
單點問題：協調者在 2PC 中起到非常大的作用，發生故障將會造成很大影響。特別是在階段二發生故障，所有參與者會一直等待狀態，無法完成其它操作
參與者依賴：任意一個節點失敗就會導致整個事務失敗

補充事務（TCC）

高可靠
實時高

開發複雜，需帶有業務補償機制
事務狀態管理，需要多次DB操作，有一定的性能損失
最終一致性

Saga

易於理解
松耦合，避免服務間依賴關係
實時高

開發複雜，需帶有業務補償機制
最終一致性

Seata

高性能
易於使用
支持AT, TCC, SAGA, XA 模式

改造成本大：相關程序都要加入Seata事務

性能損失：Seata本身存在一定的性能損耗"}}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"結合Freewheel強一致性業務需求，多數據源分佈式事務將由XA、2PC和Seata這些解決方案組合而成。"}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Seata 框架設計思想"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"基於 XA 的 Aurora 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(TM)："},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 控制全局事務的邊界，負責開啓一個全局事務，並最終發起全局提交或全局回滾的決議。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"Resource Manager (RM)："},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 控制分支事務，負責分支註冊、並接收事務協調器的指令，驅動分支（本地）事務的提交和回滾。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"爲了預防死鎖，並且減少 DAL RM 和 TC 之間的交互，降低對TC的依賴，同一個分佈式事務操作放在同一個DAL節點，由此，DAL RM可以方便的在單節點控制和協調分支事務，完成全局事務的提交和回滾。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"以多服務，不同數據源(Aurora與DynamoDB)爲例，描述Freewheel分佈式事務過程。"}]},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"A Service TM 向 TC 申請開啓一個全局事務，全局事務創建成功並生成一個全局唯一的 XID。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"XID 在微服務調用鏈路的上下文中傳播。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"TM 向 TC 發起針對 XID 的全局提交或回滾決議。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"TC 向DAL RM 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Operation

Other Operation

Isolation Level

DisTxDAL

可序列化

DisTxDAL

DAL DDB write interface

可序列化

DisTxDAL

DAL DDB read interface

讀取已提交|讀取未提交（可選）"}}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"更新接口實現方法"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 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create	None	item: item value operation:create xid: xid value	item: item value ~~operation:create~~ ~~xid: value~~	None
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