In a previous post looking at how to use Azure Key Vault to store secrets for a DevOps pipeline, we touched on variable groups and how they can be used. In this post, we’re going to dive a bit deeper into what a variable group is, how you can create one and how you can link variable groups into your build pipeline.
What is a variable group?
A variable group is a logical collection of environment variables (or properties) used throughout your build and/or deployment pipelines. They are essentially key value pairs, that can include things like API keys, database connection strings or configuration items such as downstream API endpoint URLs.
Variable groups can store both plain text variables and secrets, which should never be committed into your source code repository. Note that if you want to use DevOps’ Azure Key Vault integration, you’ll need to create a separate variable group as you can’t mix and match Key Vault and DevOps variables in the same group.
How do I create one?
Creating a variable group is simple. Login to Azure DevOps and navigate to “Pipelines” > “Library”. You’ll see in the top navigation bar the option to “+ Variable Group”. Clicking that will take you to a “New variable group” screen, that asks for a number of properties:
- Variable group name: A friendly name used to refer to your new variable group. Use something that has meaning to you and the types of properties that will be stored within the group (ie. My App - Production)
- Description: Provide a short description that describes a bit more about the types of variables that should be placed within this group (eg. This group contains build settings and environment variables for production builds only)
- Allow access to all pipelines: Enable this toggle to ensure that you can access all the variables from all of your pipelines. If you don’t enable it, you’ll need to authorise pipelines defined in YAML manually in order to let them access your properties.
- Link secrets from an Azure key vault as variables: Enable this toggle if you want to use Azure Key Vault to store your secrets instead of DevOps. Note that by enabling this, you’ll need to then provide key vault connection details, and enter your secrets via the Azure Portal instead.
If you left the key vault integration disabled, you’ll now be able to click “Add” below the “Variables” section to begin creating new properties. Each property can have a name and a value, and can be marked as clear text or secret by clicking the padlock icon at the end of each row.
If you need to customise security permissions, click “Security” at the top of the screen. This will bring up a modal window where you can add or remove user groups from being able to access this variable group.
Once you’re done, hit “Save” and your variable group will be persisted.
How do I use it?
If you selected “Allow access to all pipelines” when creating the variable group, linking it with your build pipeline through the DevOps website is simple. Navigate to the pipeline you want to link the group with, click “Edit” in the top-left corner and then click “Variables” underneath your pipeline name.
You should see on the left-hand side “Pipeline variables” and “Variable groups”. Navigate to the latter, and click “Link variable group”. This brings up a modal that lists all the variable groups that your role has access to - if you can’t see a group that you know exists, check to make sure you have set the right permissions in the “Security” window for that group.
Choose the group you want to link with the pipeline, and then the scope that the group applies to. If the variables are used throughout the pipeline, then you can choose to make it visible to the entire release, or if you know only a few scopes require access you can also choose specific scopes.
Click “Link” and you’ve now made the variable group be accessible from your pipeline!
Alternatively, if you’re using a YAML file to describe your pipelines and builds, you can also add a variable group by adding the following section in your YAML file:
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One thing worth noting is that when you run a pipeline, DevOps will create an immutable snapshot with the values of the variables within your group so that your release remains in the same state. This ensures that it isn’t influenced by future changes or modifications that you might make to the values, and means you can redeploy a release later if needed.
Summary
Variable groups can be powerful tools for logically grouping properties and secrets that you need for build pipelines, and are simple to configure and use.