feat(ec2): add support for environment files and variables in systemd

[razin99]

Reason for this change

Allow users to define Environment and EnvironmentFile in a systemd service file.

Description of changes

Added 2 new properties for ec2.InitService.systemdConfigFile:

1. environmentVariables which is a string key value pair
2. environmentFiles which is a list of file paths

Description of how you validated changes

I have added a unit test.
Documentations referred to:

• https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#EnvironmentFile=
• https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#Environment=

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

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[razin99]

Exemption Request

No README updates needed since this added optional features that goes beyond basic systemd service creation

[lpizzinidev]

Thanks for contributing 👍
Left some comments for minor adjustments.
Also, you could add some documentation in Configuring Instances using CloudFormation Init (cfn-init).

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[lpizzinidev]

Thanks 👍 Added a suggestion to change the wording for the documentation

[razin99]

@lpizzinidev what do I do from here? Never got a PR this far in this repo. Do I just wait for it to be merged?

[lpizzinidev]

Hey @razin99 ✋
First, nice job if this is one of your first PRs!
Now, you need to wait for another round of reviews from one of the core team members.
After the subsequent changes are approved, your PR will be merged 👍

[TheRealAmazonKendra]

Thank you for your work on this. I'm thinking that it's likely that this change is good to go with one clarifying question: can a user provide both environmentVariables and environmentFiles or is it an either/or situation?

If they can provide both, this looks ready.

[razin99]

Thank you for your work on this. I'm thinking that it's likely that this change is good to go with one clarifying question: can a user provide both environmentVariables and environmentFiles or is it an either/or situation?

If they can provide both, this looks ready.

They can provide both, as this is a supported behaviour by systemd. From what I've read (here), anything EnvironmentFile can override Environment

Quote from documentation:

Settings from these files override settings made with Environment=. If the same variable is set twice from these files, the files will be read in the order they are specified and the later setting will override the earlier setting.

[GavinZZ]

Thanks for answering the questions and making contribution to CDK repo. Approving on behalf for Kendra since her question is answered and this PR looks good to me.

[mergify]

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[mergify]

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Pull request has been modified.

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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• Commit ID: d701f4c
• Result: SUCCEEDED
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[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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