MongoDB's mongodump cannot export data. How to deal with it?

When mongodump fails to export data, follow these steps to diagnose and resolve the issue:

1. Check Error Messages

• Run mongodump with the --verbose flag to get detailed logs:

  mongodump --uri="mongodb://username:password@host:port/database" --verbose
  

• Common errors include authentication failures, network issues, or insufficient permissions.

2. Verify Connection and Authentication

• Ensure the connection string (--uri) is correct, including the username, password, host, port, and database name.
• Test connectivity using mongo shell or mongosh:

  mongosh "mongodb://username:password@host:port/database"
  

• If authentication fails, check if the user has the read role for the target database.

3. Check Network and Firewall Rules

• Ensure the MongoDB port (default: 27017) is open and accessible from the machine running mongodump.
• If connecting to a cloud-hosted MongoDB (e.g., TencentDB for MongoDB), verify the whitelist settings to allow the client IP.

4. Disk Space and Permissions

• Ensure sufficient disk space on the target machine for the exported data.
• Verify write permissions in the output directory (e.g., --out=/path/to/dump).

5. Use Tencent Cloud Tools (if applicable)

• If using TencentDB for MongoDB, consider using Tencent Cloud Database Backup instead of mongodump for managed backups.
• For custom exports, Tencent Cloud provides VPC peering and security groups to ensure stable connectivity.

6. Alternative: Use mongoexport for Specific Collections

• If mongodump fails for the entire database, try exporting individual collections with mongoexport:

  mongoexport --uri="mongodb://username:password@host:port/database" --collection=collection_name --out=collection_name.json
  

Example: Successful mongodump Command

mongodump --uri="mongodb://admin:password123@127.0.0.1:27017/mydb" --out=/backup/mongodb_dump

If the issue persists, check MongoDB server logs (/var/log/mongodb/mongod.log) for additional clues.