I need Terraform to retrieve a Network data by name

Question

I need to retrieve data of an existing or not Network and if it's not then it should be created i need to integrate this script in CI/CD pipeline

this is my code

data "openstack_networking_network_v2" "existed_network" {
  name          = "Network-name"
}

resource "openstack_networking_network_v2" "edums_network" {
  count  = data.openstack_networking_network_v2.existed_network.[*].id == "" ? 1:0
  name   = "Network-name"
}

i end up with this error when the network is not created Error: Your query returned no results. Please change your search criteria and try again.

Answer 1

This is a well-known issue (discussed for instance in Data sources should allow empty results without failing #16380, Terraform Data with No Results or here: Terraform check if resource exists before creating it).

In Terraform, data sources are used to retrieve details about external resources, which are not managed by Terraform itself. Essentially, data sources act as a link between the existing infrastructure and the intended configuration, facilitating a more adaptive and context-aware approach to provisioning.

Terraform does not support empty data sources:

In general data sources will fail if the resource being requested doesn’t exist. They are expected to be used to reference resources that are not managed by Terraform (or by a different Terraform root module/state).

(from https://discuss.hashicorp.com/t/terraform-data-with-no-results/47228/2)

Conditional Creation of Objects

Terraform recommends to use variables.

Quotes from Conditional Creation of Objects:

Rather than trying to write a module that itself tries to detect whether something exists and create it if not, we recommend applying the dependency inversion approach: making the module accept the object it needs as an argument, via an input variable.

This is consistent with Terraform's declarative style: rather than creating modules with complex conditional branches, we directly describe what should already exist and what we want Terraform to manage itself.

Solution

For this case (creating a network in OpenStack only if it does not already exist) there are two possible approaches, either using a variable or with import.

With a variable

variable "existing_network_name" {
  description = "Name of existing or to-be-created network in Terraform."
  default      = null
 }


resource "openstack_networking_network_v2" "edums_network" {
count  = var.existing_network_name == null ? 1:0
name   = "Network-name"
}

Define the variable in terraform.tfvars:

existing_network_name = "Network-name"

or pass it as a command-line argument:

terraform apply -var existing_network_name = "Network-name"

With `import`

openstack_networking_network_v2 supports import using the existing network's id (see Terraform Openstack provider documentation for networking_network_v2)

With an import block:

import {
  to = openstack_networking_network_v2.edums_network
  id = "i-abcd1234"
}


resource "openstack_networking_network_v2" "edums_network" {
  name   = "Network-name"
}

Again, the network ID must exist; otherwise, Terraform will generate an error message.