How to do environment variable substitution with AWS CoPilot

Question

I need to do environment variable substitution from a value from a SSM secret (secrets section in manifest). But escaping doesn't work as the doco mentioned.

variables:
  TEST1: "https://\\${DATABASE_SERVER}:5000/ReportServer?"
  TEST2: https://\${DATABASE_SERVER}:5000/ReportServer?
secrets:                      # Pass secrets from AWS Systems Manager (SSM) Parameter Store.
  DATABASE_SERVER: /database/server

I am getting the following error: ✘ interpolate environment variables for fisherassist-api manifest: environment variable "DATABASE_SERVER" is not defined

Answer 1

Firstly, this feature was released in copilot CLI v1.33.0 and I was using a older version. Got support from a ever so helpful mate from copilot gitter community 🙏🏼

Secondly, composing Run time variables from other variables is not possible with Copilot at the moment. A similar feature request is there for this.

There are 2 workarounds to achieve this.

Approach 1

1. Importing the SSM parameter in environment addon as a template parameter
2. Output the composed value
3. Import the output in the workload manifest as environment variable

Approach 2

This is a bit complicated workaround is possibly modifying the ENTRYPOINT

1. Create an entrypoint script (entrypoint.sh): This script will export TEST1 and TEST2 using the current value of DATABASE_SERVER and then run your application.

#!/bin/sh
export TEST1="https://${DATABASE_SERVER}:5000/ReportServer?"
export TEST2="https://${DATABASE_SERVER}:5000/ReportServer?"

# Now execute the main process of the container

exec "$@"

2. Modify your Dockerfile

# Copy the entrypoint script into the container
COPY entrypoint.sh /entrypoint.sh
# Set the script as the entry point
ENTRYPOINT ["/entrypoint.sh"]
CMD ["your_application_start_command"]

3. In your workload manifest you need

secrets:
  DATABASE_SERVER: /database/server

This way the DATABASE_SERVER environment variable can be passed at runtime, and entrypoint.sh will set TEST1 and TEST2 accordingly.