user-data scripts do not run on Windows workers

[NerdyMcNerd]

Describe the bug

On Windows workers, user-data does not run, because the module uses base64gzip and Windows does not accept gzip only zip.

To Reproduce

• Setup a runner using the example examples/runner-windows
• Enable SSM Access by setting runner_worker.ssm_access to true
• Set the variable runner_worker_docker_autoscaler_instance.start_script to:

  <powershell>
  New-Item -ItemType Directory -Force -Path "C:\test-dir-to-prove-script-ran"
  </powershell>

• Run a CI Job on that runner (something that takes some time)
• While that runs, access the instance that gets created via SSM
• Check the directory "C:\test-dir-to-prove-script-ran" -> it is not created.
• Check the EC2 Launch Log file C:\ProgramData\Amazon\EC2Launch\log\agent.log
  It ends with:

  Warning: No XML or YAML user-data detected. If XML or YAML user-data is intended, check for typos or refer to documentation (https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/ec2launch-v2-settings.html#ec2launch-v2-example-user-data):
  %!w(*fmt.wrapError=&{Failed to unmarshal user-data as YAML: yaml: control characters are not allowed 0xc00010f610})

Additional context

I tracked it down to the fact that the module uses gzip to compress the user-data, and Windows cannot handle gzip compressed user-data.

According to the AWS Docs EC2Launch supports zip.

See docker_autoscaler.tf line 13: the variable runner_worker_docker_autoscaler_instance.start_script is passed to the function base64gzip which is the culprit.

I performed a second test with some click-ops:

• Took the user-data and zipped them with 7-zip (standard Zip deflate)
• Then base64 encoded that zip file (cat userdata.zip | base64 > userdata.zip.b64)
• Set the resulting content as user-data in the launch template
• Changed the Auto Scaling Group to use the new version of the launch template
• Triggered a CI job
• -> The user-data ran.

[kayman-mk]

Thanks for the detailed description. As you mention that standard zips are working: Why not zipping the script? I remember problems with scripts being too big.

EDIT:
Ah, found the answer: There is no base64zip function available.