If you can access the AWS_CONTAINER_CREDENTIALS_RELATIVE_URI environment variable from within the container and the Rails console but not from within the application, it's possible that the environment variable is not being propagated correctly to the application context.
Here are a few steps to troubleshoot the issue:
Check the shell environment of the user running the Rails application inside the container. Ensure that the environment variable AWS_CONTAINER_CREDENTIALS_RELATIVE_URI is indeed present in the environment variables of the user running the Rails application. You can do this by running the following command within the container:
echo $AWS_CONTAINER_CREDENTIALS_RELATIVE_URI
If the environment variable is not visible here, then it's likely not being set properly in the container's runtime environment.
Verify the application's environment and how it's being loaded. In Rails, environment variables can be loaded from various places like config/application.rb, config/environments/*.rb, or even through gems. Check these files to ensure that there's no override or specific configuration that might be causing the variable not to be accessible.
Check if there's any code in the Rails application that might be unsetting or altering the value of AWS_CONTAINER_CREDENTIALS_RELATIVE_URI. This could happen if there's any code that sets or changes the value of environment variables programmatically.
Confirm that the application is indeed running within the same container context where you can see the environment variable. Sometimes, in complex setups, there might be multiple containers involved, and the application could be running in a different container than the one you are checking.
If you've checked everything and the issue persists, try a simple test. Create a minimal Rails application with just a single controller that prints the value of AWS_CONTAINER_CREDENTIALS_RELATIVE_URI in a response. Deploy this minimal application to Fargate and see if it can access the variable correctly. This can help you isolate if the problem is related to your application's configuration or if there's something else going on.
Ensure you have the correct IAM permissions set for the Fargate task to access the AWS credentials. Verify that the task role associated with your Fargate task has the necessary permissions to access the AWS services that your Rails application intends to interact with.
Consider logging the environment variables within your Rails application. You can add logging statements to print the value of AWS_CONTAINER_CREDENTIALS_RELATIVE_URI when your application starts up or when specific requests are handled. This can help you debug and see if the variable is being set correctly at runtime.
Remember that environment variables can behave differently based on the shell and the context in which they are accessed. If the variable is accessible in one context (e.g., Rails console) but not in another (e.g., Rails application), it indicates there might be something specific to the application's setup or environment that is affecting the variable's availability.
If you've tried all of the above and still cannot access the environment variable within your Rails application, consider reaching out to the AWS support or developer community forums for further assistance, as there might be specific AWS or Fargate-related considerations that could be causing the issue.
