Can't pass an already existing db_subnet_group: `value of 'count' cannot be computed` about terraform-aws-rds HOT 3 CLOSED

The issue you are describing is related to the way computed values work in Terraform, and currently, it is one of the most popular problems within Terraform modules. So, yes, values should be known/computed before using them in count. One of the solutions to this is to split your code into two pieces - one create aws_db_subnet_group and output name, another reads this value.

The solution you are proposing may also work, but it will not allow creating resources with the same names in the same AWS account (for example, when we need to have several similar RDS resources in test/staging AWS account).

I don't know better solution at the moment, though I am open to working suggestions and solutions.

from terraform-aws-rds.

The only workaround I found so far is to create a db_subnet_group with a deterministic name (using name instead of name_prefix) and passing that (a simple string) to the RDS module.

I guess this is somehow related with #42, as if you are able to set the name in a deterministic way you can reuse the db_group_name created inside RDS module for another RDS call (create a slave of a previously created master, for instance).

from terraform-aws-rds.

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.

from terraform-aws-rds.