Amazon Web Services Elastic Beanstalk (AWS EB) is a robust service designed to leverage AWS resources efficiently for deploying and managing applications in the cloud. However, while deploying applications, encountering errors is inevitable. One such error is the "Incorrect application version found on all instances," which can halt deployment processes. This article delves into the error, its implications, and how to address it effectively.

Understanding the Error

When using AWS Elastic Beanstalk, applications are organized in different versions, which allows easy rollback and management. The error "Incorrect application version found on all instances" typically arises during deployment when the application version on an EC2 instance doesn't match the expected version in Elastic Beanstalk.

Common Causes

1. Configuration Drift: Auto-scaling or load-balancing might cause new instances to spin up with different AMI configurations, leading to discrepancies in the deployed version.
2. Failed Updates: An update might not completely propagate due to network issues, permissions, or hitting service limits.
3. Manual Interventions: Direct changes on EC2 instances not followed through on the Elastic Beanstalk version repository.
4. Corrupted Deployments: The deployment artifact might be corrupted due to errors in the build pipeline or during upload.

Technical Explanations

Application Version Mismatch

AWS Elastic Beanstalk uses a versioning system to keep track of application developments. During a deployment, Elastic Beanstalk expects a certain version of the application to ensure consistent application performance and faster rollbacks when necessary. If any instance runs a different version than expected, it results in the error.

Debugging Steps

• Review Elastic Beanstalk Logs: Use the AWS Management Console to navigate to the Elastic Beanstalk environment and review logs. Look for discrepancies or errors related to application versions.
• Check EC2 Instance Logs: SSH into your EC2 instances, check for log files typically located in /var/log/eb-activity.log .
• Verify Deployment History: Use the AWS CLI or Management Console to confirm the version history and ensure that version propagation to all instances is complete.
• Update or Redeploy: If issues persist, consider redeploying the latest version with proper validations, or initiate an environment update.