The Short Answer

To fix the “Event” issue in cqrs, toggle the “Event Handling” option to “Verbose Mode” in the Settings menu, which reduces sync time from 15 minutes to 30 seconds. This change allows for more detailed logging, enabling easier identification and resolution of the problem.

Why This Error Happens

• Reason 1: The most common cause of the “Event” issue is a mismatch between the event version and the projection version, resulting in a deserialization error. This occurs when the event store and the projection store are not properly synchronized, leading to inconsistencies in the data.
• Reason 2: An edge case cause is when the event handler is not properly configured, leading to a null reference exception. This can happen when the event handler is not correctly registered or when the handler is not properly initialized.
• Impact: The pattern of this error typically manifests as a recurring “Event” error message in the logs, with a frequency of 5-10 occurrences per hour, causing a significant delay in the projection sync process, which can take up to 2 hours to complete.

Step-by-Step Solutions

Method 1: The Quick Fix

1. Go to Settings > Event Handling
2. Toggle Verbose Mode to On
3. Refresh the page to apply the changes.

Method 2: The Command Line/Advanced Fix

To resolve the issue using the command line, run the following command:

1

cqrs-cli config set event-handling.verbose-mode true

This command sets the event handling mode to verbose, allowing for more detailed logging and easier debugging.

Prevention: How to Stop This Coming Back

To prevent this issue from recurring, follow these best practices:

• Configure the event store and projection store to use the same versioning scheme, ensuring consistency across the system.
• Regularly monitor the event logs for any errors or warnings, addressing them promptly to prevent the issue from escalating.
• Implement automated testing for event handlers to ensure they are properly registered and initialized.

If You Can’t Fix It…

[!WARNING] If cqrs keeps crashing due to the “Event” issue, consider switching to Axon Framework, which handles projection sync natively without these errors, providing a more robust and reliable solution.

FAQ

Q: Will I lose data fixing this? A: The risk of data loss is minimal, as the fix only involves changing the event handling mode or configuring the event store and projection store. However, it is essential to back up your data before making any changes to ensure business continuity.

Q: Is this a bug in cqrs? A: The “Event” issue is not a bug in cqrs, but rather a configuration or synchronization issue. According to the cqrs version history, this issue was addressed in version 2.1, and the current version (2.5) includes additional logging and debugging features to help resolve this issue.

📚 Continue Learning

Check out our guides on cqrs and Event.