502 Bad Gateway during deploy with amazon linux 2023

The 502 Bad Gateway errors you're experiencing during deployments with Amazon Linux 2023 could be caused by several factors. Here are some potential reasons and solutions to consider:

1. Connection issues: The load balancer might be unable to establish a connection with your backend instances during the deployment. This could be due to security group configurations or network settings that need adjustment for the new Amazon Linux 2023 environment.

2. Application startup time: Your application might need more time to start up on the new system. Consider increasing the deregistration delay on your target group to allow more time for in-flight requests to complete before the instance is removed from the load balancer.

3. Health check configuration: Ensure that your health check settings are appropriate for your application on Amazon Linux 2023. You may need to adjust the health check path, interval, or timeout to better accommodate your application's behavior during deployment.

4. Apache configuration: Since you mentioned moving away from mod_php, verify that your Apache configuration is correct for the new setup. Ensure that it's properly configured to communicate with your application, especially if you're now using a different method like PHP-FPM.

5. Deployment process: Review your deployment process to see if there's a way to implement a rolling update or blue-green deployment strategy. This could help minimize downtime and reduce the occurrence of 502 errors during deployments.

6. Application code: Check if there are any application-specific issues that might be causing problems during startup or when handling requests immediately after deployment.

To address these issues:

1. Review and adjust your security group and network configurations if necessary.
2. Increase the deregistration delay in your target group settings.
3. Fine-tune your health check settings to ensure they accurately reflect your application's health.
4. Double-check your Apache and PHP configurations for any misconfigurations.
5. Consider implementing a more robust deployment strategy like rolling updates or blue-green deployments.
6. Enable detailed logging in your application and Apache to gather more information about what's happening during the deployment process.

By systematically addressing these potential issues, you should be able to reduce or eliminate the 502 Bad Gateway errors during your deployments on Amazon Linux 2023.
Sources
Health checks failed with these codes: [502] | AWS re:Post
502 bad Gateway Logo LWE To Elasticbeanstalk | AWS re:Post
How to debug 502 errors on ELB | AWS re:Post