Connection Troubleshooting连接故障排除

Configure Your Firewall配置防火墙

Verify that the ports your MongoDB deployment listens on are not blocked by a firewall on the same network. MongoDB uses port 27017 by default. To learn more about the default ports MongoDB uses and how to change them, see Default MongoDB Port in the MongoDB Server manual.验证MongoDB部署监听的端口是否未被同一网络上的防火墙阻止。默认情况下，MongoDB使用端口27017。要了解更多关于MongoDB使用的默认端口以及如何更改它们的信息，请参阅MongoDB服务器手册中的默认MongoDB端口。

Check Your Network Access List检查您的网络访问列表

Verify that your IP Address is listed in the IP Access List for your cluster. You can find your IP Access List in the Network Access section of the Atlas UI. 验证您的IP地址是否列在群集的IP访问列表中。您可以在Atlas UI的网络访问部分找到您的IP访问列表。To learn more about how to configure your IP Access List, see the Configure IP Access List Entries guide in the Atlas documentation.要了解有关如何配置IP访问列表的更多信息，请参阅Atlas文档中的“配置IP访问清单条目”指南。

Ensure MongoDB and Your Client Use the Same IP Address确保MongoDB和您的客户端使用相同的IP地址

In Node.js v17 and later, the DNS resolver uses IPv6 by default when both the client and host support both. For example, if MongoDB uses IPv4 and your client uses IPv6, the driver returns the previous error message.在Node.js v17及更高版本中，当客户端和主机都支持IPv6时，DNS解析器默认使用IPv6。例如，如果MongoDB使用IPv4，而您的客户端使用IPv6，驱动程序将返回之前的错误消息。

You can configure your MongoDB deployment to use IPv6 mode when starting with mongod or mongos. For more information about how to specify IPv6 mode, see IP Binding in the server manual.您可以将MongoDB部署配置为在从mongod或mongos开始时使用IPv6模式。有关如何指定IPv6模式的更多信息，请参阅服务器手册中的IP绑定。

As an alternative, you can explicitly use IPv4 with your client by specifying family: 4 as an option to your MongoClient.作为另一种选择，您可以通过将family:4指定为MongoClient的选项，明确地在客户端中使用IPv4。

const client = new MongoClient(uri, {
  family: 4,
});

Control the Number of File Descriptors控制文件描述符的数量

A file descriptor is a unique identifier associated with an open process. In most operating systems, each open connection from the driver is associated with a file descriptor. Operating systems typically have a limit on the number of file descriptors used by a single process. 文件描述符是与打开的进程相关联的唯一标识符。在大多数操作系统中，来自驱动程序的每个打开的连接都与一个文件描述符相关联。操作系统通常对单个进程使用的文件描述符的数量有限制。An ECONNRESET error can occur if the number of connections exceeds this limit.如果连接数超过此限制，则可能会出现ECONNRESET错误。

You can set the maximum number of connections by setting maxPoolSize. To resolve this error, you can decrease the number of maximum allowed connections by setting the value of maxPoolSize. 您可以通过设置maxPoolSize来设置最大连接数。要解决此错误，您可以通过设置maxPoolSize的值来减少允许的最大连接数。Alternatively, you could increase the file descriptor limit in your operating system. To learn more about how to set maxPoolSize, see the API documentation for maxPoolSize .或者，您可以增加操作系统中的文件描述符限制。要了解有关如何设置maxPoolSize的更多信息，请参阅maxPoolSize的API文档。

Check Your Connection String检查您的连接字符串

An invalid connection string is the most common cause of authentication issues when you attempt to connect to MongoDB by using SCRAM-SHA-256.当您尝试使用SCRAM-SHA-256连接到MongoDB时，无效的连接字符串是身份验证问题的最常见原因。

If your connection string contains a username and password, ensure that they are in the correct format. If the username or password includes any of the following characters, they must be percent encoded:如果您的连接字符串包含用户名和密码，请确保它们的格式正确。如果用户名或密码包含以下任何字符，则必须对其进行百分比编码：

: / ? # [ ] @

The following example shows how to percent encode "#MyP@assword?":以下示例显示了如何进行百分比编码"#MyP@assword?"：

console.log(encodeURIComponent('#MyP@assword?'));

This results in the following output:这将产生以下输出：

"%23MyP%40assword%3F"

Verify the User Is in the Authentication Database验证用户是否在身份验证数据库中

To successfully authenticate a connection by using a username and password with SCRAM-SHA-256, the username must be defined in the authentication database. 要使用SCRAM-SHA-256的用户名和密码成功验证连接，必须在身份验证数据库中定义用户名。The default authentication database is the admin database. To use a different database for authentication, specify the authSource in the connection string. 默认的身份验证数据库是admin数据库。若要使用其他数据库进行身份验证，请在连接字符串中指定authSource。The following example instructs the driver to use users as the authentication database:以下示例指示驱动程序将users用作身份验证数据库：

const { MongoClient } = require("mongodb");
const uri = "mongodb://<db_username>:<db_password>@<hostname>:<port>/?authSource=users";
const client = new MongoClient(uri);

Check the User Permissions检查用户权限

Verify that you've accessed the MongoDB deployment with the correct user. The term "message" in the error can be a command sent by the driver. If you are using a user that doesn't have permissions to send the command, the driver could generate this error.验证您是否已使用正确的用户访问了MongoDB部署。错误中的“消息”一词可以是驱动程序发送的命令。如果您使用的用户没有发送命令的权限，驱动程序可能会生成此错误。

Also ensure that the user has the appropriate permissions for the message you are sending. MongoDB uses Role-Based Access Control (RBAC) to control access to a MongoDB deployment. For more information about how to configure RBAC in MongoDB, see Default MongoDB Port.还要确保用户对您发送的消息具有适当的权限。MongoDB使用基于角色的访问控制（RBAC）来控制对MongoDB部署的访问。有关如何在MongoDB中配置RBAC的更多信息，请参阅默认MongoDB端口。

Configure Your Firewall配置防火墙

The firewall needs to have an open port for communicating with the MongoDB instance. For more information about configuring the firewall, see Configure Your Firewall in the Connection Error section.防火墙需要有一个开放的端口来与MongoDB实例通信。有关配置防火墙的更多信息，请参阅连接错误部分中的配置防火墙。

Check the Number of Connections检查连接数量

Each MongoClient instance supports a maximum number of concurrent open connections in its connection pool. You can configure the parameter maxPoolSize which defines this limit. The default value is 100. 每个MongoClient实例在其连接池中支持最大数量的并发打开连接。您可以配置定义此限制的参数maxPoolSize。默认值为100。If there are already a number of open connections equal to maxPoolSize, the server waits until a connection becomes available. If this wait time exceeds the maxIdleTimeMS value, the driver responds with an error.如果已存在等于maxPoolSize的打开连接数，服务器将等待连接可用。如果此等待时间超过maxIdleTimeMS值，驱动程序将返回错误。

For more information about how connection pooling works, see the Connection Pool Overview in the Connection Pools page.有关连接池工作原理的更多信息，请参阅连接池页面中的连接池概述。

Set 设置connectTimeoutMS

The driver may hang when it's unable to establish a connection because it takes too long attempting to reach unreachable replica set nodes. You can limit the time the driver spends attempting to establish the connection by using the connectTimeoutMS setting. To learn more about this setting, see the Timeout Options in the Server manual.当驱动程序无法建立连接时，它可能会挂起，因为尝试访问无法访问的副本集节点需要太长时间。您可以使用connectTimeoutMS设置来限制驱动程序尝试建立连接的时间。要了解有关此设置的更多信息，请参阅服务器手册中的超时选项。

Ensure the connectTimeoutMS setting is not lower than the highest network latency you have for a member of the set. If one of the secondary members has a latency of 10000 milliseconds, setting the connectTimeoutMS to 9000 prevents the driver from ever connecting to that member.确保connectTimeoutMS设置不低于该组成员的最高网络延迟。如果其中一个次要成员的延迟为10000毫秒，将connectTimeoutMS设置为9000会阻止驱动程序连接到该成员。

The following example sets connectTimeoutMS to 10000 milliseconds.以下示例将connectTimeoutMS设置为10000毫秒。

const client = new MongoClient(uri, {
  connectTimeoutMS: 10000,
});