Connecting to Read Replicas Using Mongo Shell

Mongo shell is the default client for the MongoDB database server. You can use Mongo Shell to connect to DB instances, and query, update, and manage data in databases. DDS is compatible with MongoDB. Mongo Shell is a part of the MongoDB client. To use Mongo Shell, download and install the MongoDB client first, and then use the Mongo shell to connect to the DB instance.

By default, a DDS instance provides a private IP address. If your applications are deployed on an ECS and are in the same region and VPC as DDS instances, you can connect to DDS instances using a private IP address to achieve a fast transmission rate and high security.

This section describes how to use Mongo Shell to connect to a read replica over a private network.

You can connect to a read replica using an SSL connection or an unencrypted connection. The SSL connection is encrypted and more secure. To improve data transmission security, connect to instances using SSL.

SSL Connection

If you connect to an instance over the SSL connection, enable SSL first. Otherwise, an error is reported. For details about how to enable SSL, see Enabling and Disabling SSL.

1. On the Instances page, click the instance name.
2. In the navigation pane on the left, choose Connections.
3. In the Basic Information area, click next to the SSL field.
4. Upload the root certificate to the ECS to be connected to the instance.

   The following describes how to upload the certificate to a Linux and Window ECS:

   • In Linux, run the following command:
     scp<IDENTITY_FILE><REMOTE_USER>@<REMOTE_ADDRESS>:<REMOTE_DIR>

     

     • IDENTITY_FILE is the directory where the root certificate resides. The file access permission is 600.
     • REMOTE_USER is the ECS OS user.
     • REMOTE_ADDRESS is the ECS address.
     • REMOTE_DIR is the directory of the ECS to which the root certificate is uploaded.
   • In Windows, upload the root certificate using a remote connection tool.

5. Connect to a DDS instance. The DDS console provides the read replica connection address. You can use this address to connect to the read replica.

   Example command:

   ./mongo "<Read replica connection address>" --ssl --sslCAFile<FILE_PATH> --sslAllowInvalidHostnames

   Parameter description:

   • Read Replica Connection Address: On the Instances page, click the instance to go to the Basic Information page. Choose Connections. Click the Private Connection tab. In the Address area, obtain the connection address of the read replica instance.
     Figure 1 Obtaining the read replica connection address
     

     The format of the read replica connection address is as follows. The database username rwuser and authentication database admin cannot be changed.

     mongodb://rwuser:<password>@192.168.xx.xx:8635,192.168.xx.xx:8635/test?authSource=admin&readPreference=secondaryPreferred&readPreferenceTags=role:readonly

     Pay attention to the following parameters in the read replica connection address:

     Table 1 Parameter description

     Parameter	Description
     rwuser	Account name, that is, the database username.
     <password>	Password for the database account. Replace it with the actual password. If the password contains at signs (@), exclamation marks (!), dollar signs ($), or percent signs (%), replace them with hexadecimal URL codes (ASCII) %40, %21, %24, and %25 respectively. For example, if the password is ****@%***!$, the corresponding URL code is ****%40%25***%21%24.
     192.168.xx.xx:8635,192.168.xx.xx:8635	IP address and port of the mongos node of the cluster instance to be connected.
     test	The name of the test database. You can set this parameter based on your service requirements.
     authSource=admin	The authentication database of user rwuser must be admin. authSource=admin is fixed in the command.

   • FILE_PATH is the path for storing the root certificate.
   • --sslAllowInvalidHostnames: To ensure that the internal communication of the cluster does not occupy resources such as the user IP address and bandwidth, the cluster certificate is generated using the internal management IP address. --sslAllowInvalidHostnames is needed for the SSL connection through a private network.

   Command example:

   ./mongo "mongodb://rwuser:<password>@192.168.xx.xx:8635,192.168.xx.xx:8635/test?authSource=admin&readPreference=secondaryPreferred&readPreferenceTags=role:readonly" --ssl --sslCAFile/tmp/ca.crt --sslAllowInvalidHostnames

   

   When connecting to an instance using the read replica connection address, add double quotation marks (") before and after the connection information.

   If the following information is displayed, the instance is successfully connected:

   mongos>

Unencrypted Connection

If you connect to an instance over an unencrypted connection, disable SSL first. Otherwise, an error is reported. For details about how to disable SSL, see Enabling and Disabling SSL.

1. Log in to the ECS.
2. Connect to a DDS instance. The DDS console provides the read replica connection address. You can use this address to connect to the read replica.

   Example command:

   ./mongo "<Read replica connection address>"

   Read Replica Connection Address: On the Instances page, click the instance to go to the Basic Information page. Choose Connections. Click the Private Connection tab. In the Address area, obtain the connection address of the read replica instance.

   Figure 2 Obtaining the read replica connection address
   

   The format of the read replica connection address is as follows. The database username rwuser and authentication database admin cannot be changed.

   mongodb://rwuser:<password>@192.168.xx.xx:8635,192.168.xx.xx:8635/test?authSource=admin&readPreference=secondaryPreferred&readPreferenceTags=role:readonly

   Pay attention to the following parameters in the private HA address:

   Table 2 Parameter description

   Parameter	Description
   rwuser	Account name, that is, the database username.
   <password>	Password for the database account. Replace it with the actual password. If the password contains at signs (@), exclamation marks (!), dollar signs ($), or percent signs (%), replace them with hexadecimal URL codes (ASCII) %40, %21, %24, and %25 respectively. For example, if the password is ****@%***!$, the corresponding URL code is ****%40%25***%21%24.
   192.168.xx.xx:8635,192.168.xx.xx:8635	IP address and port of the mongos node of the cluster instance to be connected.
   test	The name of the test database. You can set this parameter based on your service requirements.
   authSource=admin	The authentication database of user rwuser must be admin. authSource=admin is fixed in the command.

   Command example:

   ./mongo "mongodb://rwuser:<password>@192.168.xx.xx:8635,192.168.xx.xx:8635/test?authSource=admin&readPreference=secondaryPreferred&readPreferenceTags=role:readonly"

   If the following information is displayed, the instance is successfully connected:

   mongos>