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Terraform

Data Sources in Terraform resources explained with example

February 15, 2023 comments off
  • Data sources provide dynamic information about entities that are not managed by the current Terraform and configuration.
  • Variables provide static information.
  • Referencing a resource defined in a data source won’t create the resource itself, and your plan will fail if you reference nonexistent data or infrastructure.
  • Data sources allow data to be fetched or computed for use elsewhere in Terraform configuration.
  • External data sources must return information in JSON format.

This may include:

  • Configuration data from Consul
  • Information about the state of manually-configured infrastructure components
  • Another Terraform configuration
  • Defined outside of Terraform
  • Defined by another separate Terraform configuration.
data "azurerm_virtual_machine" "example" {
  name                = "simple-vm"
  resource_group_name = "demo"
}

output "virtual_machine_id" {
  value = data.azurerm_virtual_machine.example.id
}

Here’s an example of using the AWS data source in Terraform to retrieve information about an existing Amazon S3 bucket

In this example, we’re using the aws_s3_bucket data source to retrieve information about an existing S3 bucket named example-bucket. We’re then outputting several attributes of the bucket using the output block.

The aws_s3_bucket data source retrieves the specified bucket’s attributes such as bucket, region, arn, policy, id, acceleration_status, versioning, website_domain, website_endpoint, and logging as per the below documentation. https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/s3_bucket

data "aws_s3_bucket" "example" {
  bucket = "example-bucket"
}

output "bucket_name" {
  value = data.aws_s3_bucket.example.bucket
}

output "bucket_region" {
  value = data.aws_s3_bucket.example.region
}

output "bucket_arn" {
  value = data.aws_s3_bucket.example.arn
}

output "bucket_policy" {
  value = data.aws_s3_bucket.example.policy
}

Here’s an example of using the AWS data source in Terraform to retrieve information about an existing availability zone

In this example, we’re using the aws_availability_zone data source to retrieve information about the availability zone named us-west-2a in the US West (Oregon) region. We’re then outputting the zone_id and zone_name attributes of the availability zone using the output block.

The aws_availability_zone data source retrieves the specified availability zone’s attributes such as zone_id, zone_name, region_name, and opt_in_status as per the below documentation. https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/availability_zone

data "aws_availability_zone" "example" {
  state = "available"
  name  = "us-west-2a"
}

output "zone_id" {
  value = data.aws_availability_zone.example.zone_id
}

output "zone_name" {
  value = data.aws_availability_zone.example.zone_name
}
Rajesh Kumar
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