如何在cassandra集群上的数据是一致的 [英] How data will be consistent on cassandra cluster

问题描述

我有一个疑问，当我读datastax文件关于cassandra写一致性。我有一个关于cassandra如何在以下情况下保持一致状态的问题：

I have a doubt when i read datastax documentation about cassandra write consistency. I have a question on how cassandra will maintain consistent state on following scenario:

• 写一致性级别= Quorum


• 复制因素= 3

根据文档，当发生写入时，协调器节点将发送此写入请求到簇。如果一个副本成功并且其他副本失败，则协调器节点将向客户端发送错误响应，但节点1成功写入数据，并且不会回滚。

As per docs, When a write occurs coordinator node will send this write request to all replicas in a cluster. If one replica succeed and other fails then coordinator node will send error response back to the client but node-1 successfully written the data and that will not be rolled back.

这种情况下，

读取修复（或提示切换或nodetool修复）将不一致的数据从节点1复制到节点2和节点3？

Will read-repair (or hinted-handoff or nodetool repair) replicate the inconsistent data from node-1 to node-2 and node-3?

如果不是，cassandra会如何处理不能将不一致的数据复制到其他副本？

If not how will cassandra takes care of not replicating inconsistent data to other replicas?

我的问题

推荐答案

你完全正确，读修复或其他方法将更新node-2和node-3。
这意味着即使失败的写入也将最终更新其他节点（如果至少一个成功）。 Cassandra没有关系数据库具有的回滚功能。

You are completely right, the read repair or other methods will update the node-2 and node-3. This means even the failed write will eventually update other nodes (if at least one succeeded). Cassandra doesn't have anything like rollback that relational databases have.

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