Why Am I Seeing "Filter Not Found" Error and How to Fix It?

Introduction

"Filter Not Found" error typically occurs when a filter created to track events within the blockchain expires or becomes unavailable due to changes in the underlying infrastructure. In this article, we’ll explore why this happens and provide a step-by-step guide on how to resolve it.

Where does the error "Filter Not Found" comes from

The "filter not found" error typically occurs when a filter that was created to track events in a blockchain node has expired or is not available due to changes in the infrastructure on our end.

It's important to note that filters are short-lived and isolated to a specific blockchain node. If the filter is not utilized within 5-minute, it will expire.

At Chainstack, we use a cluster-based infrastructure for load balancing purposes on our Elastic Nodes. Nodes are excluded from the infrastructure whenever they fall behind the tip within a healthy threshold. If the node you are connected to gets dropped, you will be reconnected to a different and healthy node, which means that the previously created filter will not be available anymore.

How to fix the error

• To prevent the Filter from expiring, you should periodically send eth_getFilterChanges requests within 5-minute timeframes.
• We also recommend implementing an error handler, so that each time you detect the "Filter Not Found" error the new filter gets created automatically

Conclusion

By following these steps, you can effectively handle the “filter not found” error and ensure continuous event tracking in your blockchain applications. Remember to stay informed about infrastructure changes and adapt your error handling accordingly. Happy coding! 🚀

If you need further assistance, please feel free to send an email support@chainstack.com or contact our support team by opening a support ticket.