Execution order inside Terraform modules

Question

I had an issue with the execution order of modules in terraform scripts. I have raised an issue with the source repo. https://github.com/hashicorp/terraform/issues/18143

Can anyone please help me with this issue here or on GitHub?

Answer 1

The execution does not wait for the completion of the "vpc" module, but only for the availability of the value "module.vpc.vpc_id". For this it is enough to execute the aws_vpc resource. Therefore, you are not actually telling TerraForm to also wait for the consul_keys resource.

To fix this you have to add a dependency from the consul_keys resource to your other modules. This works either by :

1. Using a value exported by consul_keys in your other modules (either datacenter or var.name>)
2. Dumping the resources that depend on consul_keys in the same file.

Sadly there is no nice solution for this at the moment, but module dependencies are being worked on.

EDIT: As an example of dumping all resources in the same file:

This does not work because there are no module dependencies:

module "vpc" {
    ...
}

module "other" {
 depends_on=["module.vpc"]
}

vpc module file:

resource "aws_instance" "vpc_res1" {
    ...
}

resource "consul_keys" "my_keys" {
    ...
}

other module file:

resource "aws_instance" "other_res1" {
    ...
}

resource "aws_instance" "other_res2" {
    ...
}

Putting everything in the same file works. You can also keep the "vpc_res1" resource in a separate module:

resource "consul_keys" "my_keys" {
    ...
}

resource "aws_instance" "other_res1" {
    depends_on = ["consul_keys.my_keys"]
}

resource "aws_instance" "other_res2" {
    depends_on = ["consul_keys.my_keys"]
}