已知Mongo Shell同步操作，如何用PyMongo实现主从节点同步？

Hey there! Converting those MongoDB Shell commands to PyMongo is straightforward once you know the equivalent methods. Let's walk through each step with clear code examples:

1. Connect to the Secondary Node #

First, establish a connection to the replica set secondary node you want to configure—this replaces the mongo --host <host>:<port> shell command:

from pymongo import MongoClient

# Replace <host> and <port> with your secondary node's actual details
secondary_client = MongoClient("<host>:<port>")

2. Allow Reads from the Secondary (Equivalent to rs.slaveOk()) #

In the shell, rs.slaveOk() enables read operations on the secondary. With PyMongo, you have two reliable approaches:

Option 1: Mirror the Shell Command Directly #

Use the setSlaveOk admin command to replicate exactly what rs.slaveOk() does:

# Execute the command on the admin database
secondary_client.admin.command({"setSlaveOk": 1})

Option 2: Set Read Preference (Recommended for Modern Workflows) #

A more robust way is to define the read preference when creating the client, which ensures all subsequent reads target secondary nodes by default:

from pymongo.read_preferences import ReadPreference

secondary_client = MongoClient(
    "<host>:<port>",
    read_preference=ReadPreference.SECONDARY
)

3. Force Sync from a Specific Node (Equivalent to rs.syncFrom("<host>:<port>")) #

To tell the secondary to sync from a specific primary or peer node (instead of letting the replica set auto-select), use the replSetSyncFrom admin command via PyMongo:

# Replace <target_host>:<target_port> with the node you want to sync from
secondary_client.admin.command({"replSetSyncFrom": "<target_host>:<target_port>"})

Quick Notes to Keep in Mind #

• Permissions: Your MongoDB user needs the replSetConfigure privilege to run these replica set commands.
• Replica Set Requirement: These operations only work if the node is part of a MongoDB replica set—standalone nodes won't recognize replica set-specific commands.
• Verify Sync Status: You can check if the sync is working by running secondary_client.admin.command("replSetGetStatus") and inspecting the output for sync details.

内容的提问来源于stack exchange，提问作者DominikB1