Cassandra Session vs Cluster分享什么？ [英] Cassandra Session vs Cluster What to Share?

问题描述

关于Cassandra的Session和Cluster类（Java驱动程序）的思考，我想知道有什么区别。在Hibernate中，每次都会创建一个会话并共享该会话工厂。

Thinking about Cassandra's Session and Cluster classes (Java driver) I wonder whats the difference. In Hibernate one creates a session every time and shares the session factory.

从许多来源得知，可以考虑创建一个会话并在多个线程之间共享它。

From many sources I learned that it is considered to create a single session and share it across many threads.

我确实发现这有点古玩。我本来希望为每个线程或正在进行的操作/任务创建一个会话。

I do find this a bit curios. I would have expected that I create a session for each thread or ongoing action / task.

• 这样做时是否有问题？


• 对性能有什么影响，会话线程安全吗？


• 在较大的结果集上是否遇到游标问题（或者cassandra没有）游标？）


• 可以安全地假设Session是线程安全的吗？还是我应该注意某些极端情况？

• Do I have issues when doing so?
• Whats the performance impact and is session thread-safe?
• Do I run into cursor problems on larger result-sets (or does cassandra has no cursors?)
• Is it safe to assume that Session is thread-safe or are there edge cases I should be aware of?

推荐答案

在传统的RDBMS中，会话通常是指事务上下文，并且许多实现都不是线程安全的。同时，会话通常是在某种类型的连接池之上实现的，并且终止连接（通过错误）也会终止会话。

In traditional RDBMS, a session usually refers to a transactional context and many implementations aren't thread safe. Meanwhile, the session is usually implemented on top of some kind of connection pooling and the termination of a connection (via error) also terminates the session.

在Cassandra中，实际上没有多个调用的事务上下文，因此，一旦连接到键空间，会话就可以共享，并且不会无需重新建立。另外，驱动程序已经处理了重新连接和连接池，因此 session 与连接无关。

In Cassandra, there isn't really a transactional context over multiple calls, so once connected to a keyspace, the session shareable and doesn't need to re-established. In addition, the driver already handles reconnection and connection pooling, so sessions aren't connection dependent.

最后，针对 session 已被缓存，因此重新创建会话并不得不不断地重新准备语句效率不高。

Finally, statements prepared against a session are cached and it would be inefficient to re-create sessions and have to re-prepare statements constantly.

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