In this article, we delve into the power of Terraform Data Sources, showcasing their utility with practical examples to dynamically fetch external data in infrastructure as code.
Table of Contents
What is Terraform?
- It is an open-source IaaC (Infrastructure as a code) software tool where you define and create resources using providers in the declarative configuration language example JSON.
- With Terraform, You can package and reuse the code in the form of modules.
- It supports a number of cloud infrastructure providers such as AWS, Azure, GCP, IBM Cloud, OCI, etc.
What is Data Sources in Terraform?
Data sources in Terraform are used to get information about resources external to Terraform, and use them to set up your Terraform resources. For example, a list of IP addresses a cloud provider exposes. Data sources serve as a bridge between the current infrastructure and the desired configuration, allowing for more dynamic and context-aware provisioning.
For example, a particular IaC repository may have resource declarations for database and storage, while others may have declarations for compute resources. Thus, multiple infrastructure components are provisioned using separate Terraform projects.
In such cases as well, data sources play a crucial role in sharing the resource information, which is made available only after provisioning is complete.
Data sources allow data to be fetched or computed for use elsewhere in Terraform configuration.

Difference between terraform variables and terraform datasource
Aspect | Variables | Datasources |
---|---|---|
Purpose | Input parameters that customize configurations | Retrieve information about external resources |
Declaration | Defined using the variable block | Defined using the data block |
Scope | Local to the Terraform configuration | Global across the Terraform configuration |
Usage | Passed as arguments to resources and modules | Utilized to query external systems and APIs |
Dynamic Values | Can be assigned dynamically during execution | Fetches real-time data during execution |
Dependencies | Can depend on other variables within the scope | Can depend on other datasources and resources |
Mutable During Execution | No, values are set before execution begins | Yes, values can change during execution |
Difference between terraform resources and terraform data sources
Aspect | Resources | Datasources |
---|---|---|
Declaration | Defined using resource blocks | Defined using the data block |
Purpose | Creates, updates, or deletes infrastructure | Fetches information about external resources |
Usage | Configures and manages infrastructure state | Queries external systems and APIs |
Scope | Typically within the same Terraform file | Can be used across multiple Terraform files |
Dependency Management | Explicitly declared using depends_on | Dependencies are managed implicitly |
Mutability | Mutable – can be modified during execution | Immutable – values are read-only during execution |
Outputs | Can produce outputs for inter-resource communication | Primarily used for retrieving information |
Examples | aws_instance, aws_s3_bucket | aws_ami, aws_subnet, external |
Benefits of Utilizing Terraform Data Sources
Benefits of Data Sources: Enhance code reusability by reducing redundancy and promoting maintainability. Efficiently handle external data, fostering a dynamic approach to infrastructure management.
Common Mistakes: Beware of overlooking error handling; validate outputs, implement conditional logic, and rigorously test configurations for robust data source usage.
Real-world Use Cases: Fetch external data for networking or configuration management scenarios, showcasing data sources’ versatility in diverse infrastructure setups.
Security Measures: Prioritize security by avoiding exposure of sensitive information, employing encryption, and implementing access controls to protect Terraform configurations.
Future Developments: Anticipate Terraform’s evolution with enhanced support for cloud providers, improved filtering, and advanced querying capabilities for cutting-edge infrastructure code.
Practical to understand Terraform DataSource
Step1: Create an aws_instance
provider "aws" { region = "ap-south-1" profile = "default" } resource "aws_instance" "ec2_example" { ami = "ami-03f4878755434977f" instance_type = "t2.micro" tags = { Name = "Terraform EC2" } }
Step2: Define a data source
data "aws_instance" "myawsinstance" { filter { name = "tag:Name" values = ["Terraform EC2"] } depends_on = [ "aws_instance.ec2_example" ] }
Step3: Create Output variable for data source
output "fetched_info_from_aws" { value = data.aws_instance.myawsinstance.public_ip }
Step4: Apply the final terraform configuration
datasource.tf
provider "aws" { region = "ap-south-1" profile = "default" } resource "aws_instance" "ec2_example" { ami = "ami-03f4878755434977f" instance_type = "t2.micro" tags = { Name = "Terraform EC2" } } data "aws_instance" "myawsinstance" { filter { name = "tag:Name" values = ["Terraform EC2"] } depends_on = [ "aws_instance.ec2_example" ] } output "fetched_info_from_aws" { value = data.aws_instance.myawsinstance.public_ip }
Step5: Let’s Deploy by using Terraform Commands
terraform init
terraform plan
terraform apply
terraform destroy
Conclusion
Terraform data sources enable the retrieval of external information to inform infrastructure configuration. By defining a data source block, querying relevant data, and seamlessly integrating it into resource attributes, Terraform provides a dynamic and flexible approach. In practice, using data sources allows for efficient and automated management of diverse infrastructures, enhancing the power of Terraform configurations.
Reference:-
For reference visit the official website .
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Related Articles:
Terraform State File Management | Terraform Local State File | Terraform Remote