depends_on module not working as expected

[hafizullah]

Hi
I was looking forward to using the depends_on module feature [10076].

However it is not working as expected I think.

So my setup:
I have two modules, network and environment

In the environment module I have some resources defined(ec2 instances) that needs to depend on the network module being fully created.

For each resource that depends on network module have added:

depends_on = [
   "module.network"]

Expected:
Network module is created and then my resources that depends on it are created

Actual:

error loading Terraform: module env.root: 1 error(s) occurred:
* aws_instance.instance2: resource depends on non-existent module 'network'

I feel this is an issue but would like to be proven wrong :)

[mitchellh]

Modules are only visible in the module they're used. Within your environment module, the "network" module doesn't exist (it exists in the parent). I tried with a couple modules and resources in the same module and did you exact line above and it worked great.

[cemo]

@mitchellh What is the proper way of handling such cases? I want true isolated modules and also using some modules from 3rd party projects as a dependency which makes impossible to create nested structures.

[FilBot3]

Alright to clarify my deleted post, what I did was use a Rakefile, and split my parts of my infrastructure up into multiple plans and apply's. I have one Rake task plan and apply my network specific stuff, then another for my security groups, and a 3rd for my compute infrastructure. That kind of logically splits it up, even though they're in the same main.tf calling those modules.

This is my workaround until Terraform has a module depends_on function.

This may seem over the top, but it works.

namespace :terraform do
  namespace :openstack do
    desc 'Deploy the Full Stack, erythang'
    task deploy: ['terraform:openstack:deploy_infra', 'terraform:openstack:deploy_secgrps', 'terraform:openstack:deploy_compute']

    desc 'Use Terraform to deploy the infrastructure'
    task deploy_infra: ['terraform:openstack:plan_infra', 'terraform:openstack:apply_infra']

    task :plan_infra do
      sh %(
        terraform plan \
          -target=module.splunk_network_infra \
          -out=terraform_state/splunk_deployment_infra.tfplan \
          -state=terraform_state/terraform_infra.tfstate
      )
    end

    task :apply_infra do
      sh %(
        terraform apply \
          -target=module.splunk_network_infra \
          -state-out=terraform_state/terraform_infra.tfstate \
          terraform_state/splunk_deployment_infra.tfplan
      )
    end

    desc 'Use Terraform to deploy the security groups'
    task deploy_secgrps: ['terraform:openstack:plan_secgrps', 'terraform:openstack:apply_secgrps']

    task :plan_secgrps do
      sh %(
        terraform plan \
          -target=module.splunk_security_group \
          -out=terraform_state/splunk_deployment_secgrps.tfplan \
          -state=terraform_state/terraform_secgrps.tfstate
      )
    end

    task :apply_secgrps do
      sh %(
        terraform apply \
          -target=module.splunk_security_group \
          -state-out=terraform_state/terraform_secgrps.tfstate \
          terraform_state/splunk_deployment_secgrps.tfplan
      )
    end

    desc 'Use Terraform to deploy the compute instances'
    task deploy_compute: ['terraform:openstack:plan_compute', 'terraform:openstack:apply_compute']

    task :plan_compute do
      sh %(
        terraform plan \
          -target=module.splunk_instance_01 \
          -out=terraform_state/splunk_deployment_compute.tfplan \
          -state=terraform_state/terraform_compute.tfstate
      )
    end

    task :apply_compute do
      sh %(
        terraform apply \
          -target=module.splunk_instance_01 \
          -state-out=terraform_state/terraform_compute.tfstate \
          terraform_state/splunk_deployment_compute.tfplan
      )
    end

    desc 'Destroy the Full Stack, erythang'
    task destroy: ['terraform:openstack:destroy_infra', 'terraform:openstack:destroy_secgrps', 'terraform:openstack:destroy_compute']

    desc 'Use Terraform to destroy the infrastructure'
    task destroy_infra: ['terraform:openstack:plan_destroy_infra', 'terraform:openstack:apply_destroy_infra']

    task :plan_destroy_infra do
      sh %(
        terraform plan \
          -destroy \
          -target=module.splunk_network_infra \
          -out=terraform_state/splunk_destroy_infra.tfplan \
          -state=terraform_state/terraform_infra.tfstate
      )
    end

    task :apply_destroy_infra do
      sh %(
        terraform apply \
          -target=module.splunk_network_infra \
          -state-out=terraform_state/terraform_infra.tfstate \
          terraform_state/splunk_destroy_infra.tfplan
      )
    end

    desc 'Use Terraform to destroy the security groups'
    task destroy_secgrps: ['terraform:openstack:plan_destroy_secgrps', 'terraform:openstack:apply_destroy_secgrps']

    task :plan_destroy_secgrps do
      sh %(
        terraform plan \
          -destroy \
          -target=module.splunk_security_group \
          -out=terraform_state/splunk_destroy_secgrps.tfplan \
          -state=terraform_state/terraform_secgrps.tfstate
      )
    end

    task :apply_destroy_secgrps do
      sh %(
        terraform apply \
          -target=module.splunk_security_group \
          -state-out=terraform_state/terraform_secgrps.tfstate \
          terraform_state/splunk_destroy_secgrps.tfplan
      )
    end

    desc 'Use Terraform to destroy the compute instances'
    task destroy_compute: ['terraform:openstack:plan_destroy_compute', 'terraform:openstack:apply_destroy_compute']

    task :plan_destroy_compute do
      sh %(
        terraform plan \
          -destroy \
          -target=module.splunk_instance_01 \
          -out=terraform_state/splunk_destroy_compute.tfplan \
          -state=terraform_state/terraform_compute.tfstate
      )
    end

    task :apply_destroy_compute do
      sh %(
        terraform apply \
          -target=module.splunk_instance_01 \
          -state-out=terraform_state/terraform_compute.tfstate \
          terraform_state/splunk_destroy_compute.tfplan
      )
    end
  end
end

[ghost]

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.