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Common MongoDB errors

MongoDB is a highly popular NoSQL database utilized by many developers worldwide. While it is highly efficient and scalable, like any other software, it may occasionally throw some errors. Understanding these errors is critical to effectively using MongoDB.

In this tutorial, we will discuss some common MongoDB errors and how to resolve them. The objective is to help you troubleshoot and debug issues you may encounter while working with MongoDB.

Common MongoDB Errors

1. E11000 duplicate key error collection​

This error occurs when you attempt to insert a document with a value that already exists in the database for a field defined as unique.

Solution: Ensure that the value of the field defined as unique is genuinely unique for each document you insert into the collection.

2. Cannot connect to MongoDB errno:61 Connection refused​

This error occurs when you attempt to connect to the MongoDB server, but the server refuses the connection.

Solution: Check if the MongoDB server is running and if the connection parameters (host, port) are correct. Also, ensure that the MongoDB server is configured to accept connections from your IP address.

3. Out of memory, malloc failed​

This error generally occurs when the MongoDB server runs out of memory.

Solution: Increase the memory limit on your system or optimize your queries to use less memory.

4. Cursor not found​

This error is thrown when you attempt to get more results from a cursor that doesn't exist or has already been exhausted.

Solution: Either handle the error in your application code or ensure that the cursor exists and is not exhausted before fetching more results.

5. BSONObj size: ... is invalid. Size must be between 0 and 16793600​

This error occurs when you attempt to insert a document that exceeds the maximum BSON document size, which is 16MB.

Solution: Ensure that the documents you are inserting into your collection are smaller than 16MB.

Conclusion

The above list covers some of the most common errors you might encounter when working with MongoDB. Remember, the key to effective troubleshooting and debugging is understanding the error message and knowing where to look for solutions. Always refer to the official MongoDB documentation for detailed, up-to-date information. Keep practicing and happy debugging!

Note: Always backup your data before making significant changes to your database to avoid data loss.