1.9 KiB
Using map(string) for tag_bindings variables
authors: Julio date: Dec 19, 2024
Status
Accepted and implemented.
Context
We need to define a variable to manage tag bindings in our Terraform modules. This variable will be used across various modules and within the FAST framework to attach tags to resources via the google_tags_tag_binding resource. This variable needs to support both statically defined tags and tags that are dynamically generated during the apply phase of Terraform.
Decision:
We will use the map(string) type for the tag_bindings variable across all modules where it's needed.
Consequences
Minimal. This is already an established practice across the repository.
Note that the keys of the map are ignored by our code and only used to bypass Terraform limitations with dynamic values in a for_each argument. See Using Expressions in for_each in Terraform's documentation for more details.
Reasoning
The primary reason for choosing map(string) is to enable the use of dynamic tags without encountering Terraform errors related to dynamic values. By using a map, we avoid the limitations imposed by lists or sets and ensure that our modules and FAST can handle both static and dynamic tag values.
Alternatives Considered:
list(string): Lists would enforce a fixed number of tags defined at plan time, limiting flexibility and hindering the management of dynamic tags.set(string): Similar to lists, sets would require all tag values to be known at plan time, which is not suitable for scenarios with dynamic tag generation.
Implementation:
At the time of writing this ADR, all modules and FAST stages already use map(string). The purpose of this ADR is to document an existing practice.