Referencing Configuration Values in Pulumi YAML

Lately I’ve been doing a fair amount of work with Pulumi’s YAML support (see this blog post announcing it), and I recently ran into a situation where I wanted to read in and use a configuration value (set via pulumi config). When using one of Pulumi’s supported programming languages, like TypeScript or Python or Go, this is pretty easy. It’s also easy in YAML, but not as intuitive as I originally expected. In this post, I’ll share how to read in and use a configuration value when using Pulumi YAML.

Configuration values are how you parameterize a Pulumi program in order to make it more flexible and reusable (see this page on configuration from Pulumi’s architecture and concepts documentation). That same page also has examples of using config.Get or config.Require to pull configuration values into a program (the difference between these two, by the way, is that the latter will prevent a program from running if the configuration value isn’t supplied).

In YAML, it’s (currently) handled a bit differently. As outlined in the Pulumi YAML reference, a Pulumi YAML document has four main sections: configuration, resources, variables, and outputs. At first, I thought I’d have to use the variables section along with the Fn::Invoke function, which allows users to “call” or “invoke” some sort of programmatic function, like looking up information from a provider or similar. There are other functions as well, like Base64 encoding or decoding.

As it turns out, though, it’s actually the configuration section that is what you need to read in and use a configuration value. This seems obvious now in retrospect, but it didn’t seem obvious at first. In my case, I wanted to read in and use a configuration value for the underlying provider, like the azure-native:location configuration value used by the Azure Native provider. Here’s what’s needed:

configuration:
  azure-native:location:
    type: String

Omitting a default: <some value> line from the stanza above, like I did, means that this is a required value (i.e., it is analogous to using config.Require in a programming language).

That’s only half the picture, though. To then later reference this value somewhere else, you use the standard Pulumi YAML interpolation syntax. Continuing the example of using the azure-native:location configuration value, here’s how you would reference that configuration value when creating an Azure resource group:

resources:
  resourceGroup:
    type: azure-native:resources:ResourceGroup
    properties:
      location: ${azure-native:location}
      resourceGroupName: scotts-rg

While this example shows using a provider configuration value (the azure-native:location value), it is equally applicable to any sort of configuration value you need to pass in and reference in a Pulumi YAML document.

I hope this proves useful to someone out there. If you have questions, feel free to reach out to me on Twitter, or come find me in the Pulumi community Slack.

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