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Tuning Your Connection Pool Settings调整连接池设置

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Problem问题Solution解决方案
Slow application-side operation times that are not reflected in the database server logs or the real time panel.数据库服务器日志或实时面板中没有反映的应用程序端操作时间较慢。Use connectTimeoutMS to ensure the driver does not wait indefinitely during the connection phase.使用connectTimeoutMS确保驱动程序在连接阶段不会无限期等待。
Set connectTimeoutMS to a value greater than the longest network latency you have to a member of the set.将connectTimeoutMS设置为一个值，该值大于该集成员的最长网络延迟。
For example: if a member has a latency of 10000 milliseconds, setting connectTimeoutMS to 5000 (milliseconds) prevents the driver from connecting to that member. 例如：如果某个成员的延迟为10000毫秒，则将connectTimeoutMS设置为5000（毫秒）将阻止驱动程序连接到该成员。
A misconfigured firewall closes a socket connection incorrectly and the driver cannot detect that the connection closed improperly.配置错误的防火墙错误地关闭了套接字连接，并且驱动程序无法检测到该连接关闭不正确。Use socketTimeoutMS to ensure that sockets are always closed.使用socketTimeoutMS确保套接字始终处于关闭状态。
Set socketTimeoutMS to two or three times the length of the slowest operation that the driver runs. 将socketTimeoutMS设置为驱动程序运行的最慢操作长度的两到三倍。
The server logs or real time panel show that the application spends too much time creating new connections.服务器日志或实时面板显示应用程序在创建新连接时花费了太多时间。Not enough connections are available at startup. 启动时没有足够的可用连接。Allocate connections in the pool by setting minPoolSize.通过设置minPoolSize在池中分配连接。
Set minPoolSize to the number of connections you want to be available at startup.将minPoolSize设置为您希望在启动时可用的连接数。
The MongoClient instance ensures that number of connections exists at all times. MongoClient实例确保在任何时候都存在一定数量的连接。
The load on the database is low and there's a small number of active connections at any time. 数据库上的负载很低，并且任何时候都有少量活动连接。Application performs fewer operations at any one time than expected.应用程序在任何时候执行的操作都比预期的要少。Increase maxPoolSize, or increase the number of active threads in your application or the framework you are using.增加maxPoolSize，或增加应用程序或正在使用的框架中的活动线程数。
Database CPU usage is higher than expected. 数据库CPU使用率高于预期。The server logs or real time panel show more connection attempts than expected.服务器日志或实时面板显示的连接尝试次数超出预期。Decrease the maxPoolSize or reduce the number of threads in your application. 减小应用程序中的maxPoolSize或减少线程数。This can reduce load and response times.这可以减少负载和响应时间。
Warning

Do not use socketTimeoutMS to prevent long-running server operations. 不要使用socketTimeoutMS来阻止长时间运行的服务器操作。Instead, use maxTimeMS() with queries so that the server can cancel long-running operations.相反，在查询中使用maxTimeMS()，这样服务器就可以取消长时间运行的操作。

Calculate Maximum Number of Connections计算最大连接数

Calculate usage to find the number of operations running for each connection.计算使用率以查找每个连接运行的操作数。

Consider four application servers connecting to a replica set with three members. 考虑四个应用程序服务器连接到一个有三个成员的复制副本集。In this scenario, each of the four application servers creates a connection pool for each replica set member.在这种情况下，四个应用程序服务器中的每一个都为每个复制集成员创建一个连接池。

Calculate the maximum number of connections that are opened by each application server by multiplying maxPoolSize by the number of members.通过将maxPoolSize乘以成员数，计算每个应用程序服务器打开的最大连接数。

Calculate outgoing connections from an application to a three-member replica set:计算从应用程序到三成员复制集的传出连接：

100 (maxPoolSize default 100) x 3 (replica set members) = 300 (outgoing connections from the application).

Calculate incoming connections from four application servers to a replica set:

100 (maxPoolSize default 100) x 4 (application servers) = 400 (incoming connections to each mongod).