provider.url: Unmarshaling unknown values is not supported / postpone database connection

[adaptivegarage]

Hi there,

Terraform Version

1.3.2

Affected Resource(s)

• sql provider configuration itself

Terraform Configuration Files

provider "sql" {
    url = "postgres://${local.postgresql.login}:${local.postgresql.password}@${local.postgresql.host}:${local.postgresql.port}/postgres?sslmode=${local.postgresql.sslmode}"
}

Expected Behavior

The provider should have been configured.

Actual Behavior

The provider fails to pass configuration invoking this error:

 Error: Plugin error
│ 
│ The plugin returned an unexpected error from plugin6.(*GRPCProvider).ConfigureProvider: rpc error: code = Unknown desc = ConfigureProvider - unable to read url:
│ unmarshaling unknown values is not supported

Steps to Reproduce

Use any variable in the url parameter with a value not known during the planning phase.

Important Factoids

The connection string cannot be passed in advance in my case because the PostgreSQL server is provisioned during apply phase.
Postgresql provider (https://registry.terraform.io/providers/cyrilgdn/postgresql/) is ok with it.

[paultyng]

What does the local declaration look like. I tried to simulate this in an acceptance test but I was unable to. I'm guessing it's also reading its value from somewhere else?

[adaptivegarage]

Hi, thanks for getting back to me so quickly.
Yes, the local declaration is populated after a data resource external is fired, which turns on port forwarding to the SQL server (otherwise normally not accessible) and returns all the values needed to build the connection string. This is of course something that is not known during the planning phase, so what I am asking for is to allow the sql provider to finish its configuration during the apply phase.
It's only my rough guess that it should be feasible, because I've been using cyrilgdn/postgresql provider in the same scenario without any issues.

I also tried to populate the sql provider with fixed connection URL to a not-yet-existing SQL server and it fails too, because the provider checks connection.

Thanks a lot for looking into this.
Roman

[neo-travis-friesen]

We've run into this issue, too, is there any movement on it? Providers don't support depends_on, and using them in resources doesn't cause the provider to delay its configuration.

[CelsoSantos]

I too am running into this :(

[adaptivegarage]

Hi,
could I revisit this issue and ask whether it's feasible to modify the provider in a way that it delays the database connection until a resource is created?

I'm asking this because I believe it would fit a very common usecase:

The database, or even the server hosting it, might not be in existence at the time of initializing this provider, as it's intended to be set up yet by another Terraform resource. Using depends_on to defer this provider's resources isn't effective in this situation because the provider requires the database to be operational during the planning phase.

Thank you.