MongoDB · January 2, 2024

How to fix MongoDB Error Code - 112 - WriteConflict

How to Fix MongoDB Error Code - 112 - WriteConflict

MongoDB is a popular NoSQL database that offers high performance, scalability, and flexibility. However, like any other software, it can encounter errors that need to be resolved. One such error is MongoDB Error Code - 112 - WriteConflict. In this article, we will explore what this error means and how to fix it.

Understanding MongoDB Error Code - 112 - WriteConflict

When multiple clients or threads attempt to modify the same document simultaneously, MongoDB may encounter a write conflict. This conflict occurs when two or more operations try to modify the same document at the same time, resulting in a race condition. MongoDB detects this conflict and throws the Error Code - 112 - WriteConflict.

The WriteConflict error indicates that the write operation failed due to a conflict with another write operation. It typically occurs in scenarios where multiple clients or threads are performing concurrent writes on the same document.

How to Fix MongoDB Error Code - 112 - WriteConflict

Resolving the WriteConflict error requires implementing strategies to handle concurrent writes effectively. Here are some approaches you can take:

1. Retry the Write Operation

One way to handle the WriteConflict error is to retry the write operation. By retrying the operation, you give MongoDB another chance to successfully complete the write. Implementing a retry mechanism with an appropriate delay between retries can help mitigate the conflict.

Here's an example of how you can implement a retry mechanism in Python:

import time

def retry_write_operation(collection, document_id, update):
    max_retries = 3
    retry_delay = 0.5

    for i in range(max_retries):
        try:
            collection.update_one({"_id": document_id}, update)
            return
        except pymongo.errors.WriteConflictError:
            time.sleep(retry_delay)
            continue

    raise Exception("Write operation failed after multiple retries")

2. Use Optimistic Concurrency Control

Optimistic Concurrency Control (OCC) is a technique that allows concurrent writes to proceed without blocking each other. It involves adding a version field to each document and using it to detect conflicts. When updating a document, you include the current version in the update query. If the version has changed since you last read the document, MongoDB will throw the WriteConflict error.

To handle the WriteConflict error with OCC, you need to catch the error, fetch the latest version of the document, and retry the write operation with the updated version.

3. Implement Pessimistic Locking

Pessimistic Locking is another approach to handle concurrent writes. It involves acquiring a lock on the document before performing any write operation. This ensures that only one client or thread can modify the document at a time, preventing conflicts.

However, implementing pessimistic locking can impact performance, as it introduces contention and potential bottlenecks. It is recommended to use this approach only when necessary.

Summary

MongoDB Error Code - 112 - WriteConflict occurs when multiple clients or threads attempt to modify the same document simultaneously. To fix this error, you can retry the write operation, use Optimistic Concurrency Control, or implement Pessimistic Locking. By applying these strategies, you can handle concurrent writes effectively and prevent write conflicts in MongoDB.

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