One of the advanced features of Terraform is the ability to create custom providers, which allows you to extend Terraform’s functionality to manage resources that are not natively supported. A provider is a plugin that connects Terraform to a specific service or infrastructure platform and provides the necessary API calls to create, configure, and manage resources on that platform.

To create a custom provider, you will need to:

  1. Write Go code for the provider following the guidelines provided in the Terraform documentation
  2. Build the provider code into a binary file
  3. Install the provider binary file into the local Terraform environment

Here is an example of how you might create a custom provider for managing resources in a fictional “FooCloud” service:

> Create a new Go module for your provider, and define the provider’s schema and resource types in the provider.go file. For example:

package foo

import (
  "github.com/hashicorp/terraform-plugin-sdk/helper/schema"
)

func Provider() *schema.Provider {
  return &schema.Provider{
    ResourcesMap: map[string]*schema.Resource{
      "foo_server": resourceFooServer(),
    },
  }
}

 

>>>Implement the necessary CRUD (create, read, update, delete) functions for each of your resource types in separate files. For example, the resource_foo_server.go file might contain the following:

 

func resourceFooServer() *schema.Resource {
  return &schema.Resource{
    Create: resourceFooServerCreate,
    Read:   resourceFooServerRead,
    Update: resourceFooServerUpdate,
    Delete: resourceFooServerDelete,

    Schema: map[string]*schema.Schema{
      "name": {
        Type:     schema.TypeString,
        Required: true,
      },
      "size": {
        Type:     schema.TypeString,
        Required: true,
      },
    },
  }
}

func resourceFooServerCreate(d *schema.ResourceData, meta interface{}) error {
  // Create a new FooCloud server using the provided name and size
  // Save the server's ID as the resource's ID
  // Return any errors that occurred
}

func resourceFooServerRead(d *schema.ResourceData, meta interface{}) error {
  // Read the current state of the FooCloud server with the given ID
  // Update the resource data with the server's current name and size
  // Return any errors that occurred
}

func resourceFooServerUpdate(d *schema.ResourceData, meta interface{}) error {
  // Update the FooCloud server with the given ID using the new name and size provided in the resource data
  // Return any errors that occurred
}

func resourceFooServerDelete(d *schema.ResourceData, meta interface{}) error {
  // Delete the FooCloud server with the given ID
  // Return any errors that occurred
}

 

>>> Build the provider binary by running go build it in the provider module directory. This will generate a terraform-provider-foo binary file.

>>> Install the provider binary file into your local Terraform environment by copying it to the `~/.ter