# System rollback best practices
<a name="troubleshooting-system-rollback"></a>

With automatic system rollback and operations visibility capabilities in Amazon Managed Service for Apache Flink, you can identify and resolve issues with your applications.

## System rollbacks
<a name="troubleshooting-unsupported-kinesis-connectors-error"></a>

If your application update or scaling operation fails due to a customer error, such as a code bug or permission issue, Amazon Managed Service for Apache Flink automatically attempts to roll back to the previous running version if you have opted in to this functionality. For more information, see [Enable system rollbacks for your Managed Service for Apache Flink application](how-system-rollbacks.md). If this autorollback fails or you have not opted in or opted out, your application will be placed into the `READY` state. To update your application, complete the following steps:   Check the Amazon Managed Service for Apache Flink console or use the `DescribeApplicationOperation` API to see the error description for why the operation failed.    For the full error stack, use [Cloudwatch logs](https://docs.aws.amazon.com/managed-flink/latest/java/logging.html).   Common issues are insufficient permissions, incompatible code changes, or infrastructure misconfigurations. Resolve the underlying issue.    Use the `UpdateApplicaton` API to redeploy your new application version.    

## Manual rollback
<a name="troubleshooting-unsupported-kinesis-connectors-error"></a>

If the application is not progressing and is in a transient state for long, or if the application successfully transitioned to `Running`, but you see downstream issues like processing errors in a successfully updated Flink application, you can manually roll it back using the `RollbackApplication` API.

1. Call `RollbackApplication` - this will revert to the previous running version and restore the previous state. 

1. Monitor the rollback operation using the `DescribeApplicationOperation` API.

1. If rollback fails, use the previous system rollback steps.

## Operations visibility
<a name="troubleshooting-unsupported-kinesis-connectors-error"></a>

The `ListApplicationOperations` API shows the history of all customer and system operations on your application.

1. Get the *operationId* of the failed operation from the list.

1. Call `DescribeApplicationOperation` and check the status and *statusDescription*.

1. If an operation failed, the description points to a potential error to investigate. 

**Common error code bugs:** Use the rollback capabilities to revert to the last working version. Resolve bugs and retry the update. 

**Permission issues:** Use the `DescribeApplicationOperation` to see the required permissions. Update application permissions and retry. 

**Amazon Managed Service for Apache Flink service issues:** Check the AWS Health Dashboard or open a support case.