MongoDB：什么是连接池和超时？ [英] MongoDB: What is connection pooling and timeout?

问题描述

我使用Connection.new（localhost，3000，：pool_size => 1）连接到MongoDB， ：timeout => 5）

为什么我需要一个连接池，如果我只是在启动我的Rails应用程序，而不是每个请求开销？为什么单个进程需要多于1个连接？

超时的目的是什么？为什么我想要连接超时？难道不应该坚持通过Rails进程的生命？

这么困惑...

这个问题是针对Ruby和Mongo的，但我想它适用于其他语言/数据库。

解决方案

这里不需要使用连接池。当您使用Passenger时，只需确保每个实例通过捕获start_worker_process事件使用单独的连接。这在驱动程序README中有记录。

连接池对于某些多线程应用程序可能很有用。 pool_size是连接将处理的并发线程的最大数量，timeout是线程在抛出异常之前可以等待可用套接字的最大秒数。

So my Passenger spins up 5 instances of my Rails app

I connect to MongoDB using Connection.new("localhost", 3000, :pool_size => 1, :timeout => 5)

Why would I need a "pool of connections" if I only incur overhead when starting up my Rails app, not per request? Why would a single process need more than 1 connection?

And what is the purpose of the timeout? Why would I want the connection to timeout? Shouldn't it be persist through the Rails process' lifetime?

So confused...

This question is specific to Ruby and Mongo but I guess it applies to other languages/databases.

解决方案

You don't need to use connection pooling here. As you're using Passenger, just make sure that each instance uses a separate connection by catching the start_worker_process event. This is documented in the driver README.

Connection pooling can be useful for certain multi-threaded apps. pool_size is the max number of concurrent threads the connection will handle, and timeout is the maximum number of seconds a thread can wait for an available socket before an exception is thrown.

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