How to share environment variables across AWS CodeDeploy steps? - bash

Question

I am working on a new deployment strategy that leverages AWS CodeDeploy. The project I work on has many environments (e.g: preproduction, production) and instances (e.g: EMEA, US, APAC).
I have the basic scaffolding working ok but I noticed environment variables set in the BeforeInstall hook can not be retrieved from other steps (for instance, AfterInstall).
Is there a way to share environment variables across AWS CodeDeploy steps?
Content of appspec.yml:
version: 0.0
os: linux
files:
- source: /
destination: /tmp/code-deploy
hooks:
BeforeInstall:
- location: utils/delivery/aws/CodeDeploy/before_install.sh
timeout: 300
AfterInstall:
- location: utils/delivery/aws/CodeDeploy/after_install.sh
timeout: 300
ApplicationStart:
- location: utils/delivery/aws/CodeDeploy/application_start.sh
timeout: 300
ValidateService:
- location: utils/delivery/aws/CodeDeploy/validate_service.sh
timeout: 300
I set an environment variable in before_install.sh:
export ENVIRONMENT=preprod
And if I reference it in after_install.sh:
$ echo $ENVIRONMENT
$
Nothing.
Thank you for your help on this one!

Answer 1

You could put the export into a temporary file, and then, source that file. So within before_install.sh:
ENVIRONMENT="preprod"
echo "export ENVIRONMENT=\"$ENVIRONMENT\"" > "/path/to/file"
Note: With this method, you are no longer exporting the variable in before_install.sh. You are simply writing a file to be sourced in after_install.sh:
source "/path/to/file"
echo "$ENVIRONMENT"

Answer 2

You should consider setting those variables up in the userdata phase of the instance launch, instead of at deploy time. This allows them to be available to all codedeploy scripts during the life of the instance.
The type of data you describe eg Environment is more associated with the instance itself, and would not normally change during code deployment.
In your Userdata you would set an instance level variable like this:
export ENVIRONMENT="preprod" >> /etc/environment
Another advantage of this approach is that your app itself may want to consult these variables when it launches, to provide environment specific configuration.
If you use Cloudformation, you can set the environment up as a parameter, and pass that on to the user data script. In this way, you can launch the stack and its resources with the appropriate parameters, and launch consistent instances for any environment.