Introduction to Infrastructure as Code (IaC): Terraforming your Infrastructure Part2
Tags: iac, terraform, provision, automation
Published: 2023-06-05 08:58:43

### Introduction:
In our previous article, we explored the concept of Infrastructure as Code (IaC) and the challenges that led to its emergence as a game-changer in the management of cloud infrastructure. We discussed how IaC addresses the limitations of traditional manual approaches, enabling organizations to provision, configure, and manage infrastructure resources in a consistent, scalable, and automated manner.

In our previous article, we explored the concept of Infrastructure as Code (IaC) and the challenges that led to its emergence as a game-changer in the management of cloud infrastructure. We discussed how IaC addresses the limitations of traditional manual approaches, enabling organizations to provision, configure, and manage infrastructure resources in a consistent, scalable, and automated manner.

Terraform embraces a declarative approach, allowing users to define infrastructure configurations using a simple and human-readable domain-specific language (DSL). With Terraform, infrastructure configurations become versionable, repeatable, and easily shareable, bringing the benefits of collaboration, automation, and repeatability to infrastructure management.

### Common Terraform Terms:
Here are some of the common terms and concepts used in Terraform. Understanding these terms will help you navigate and effectively work with Terraform's configuration files and commands to provision and manage your infrastructure:
- **Provider**: A provider in Terraform is a plugin that interacts with a specific infrastructure platform or service. Providers enable Terraform to manage resources offered by different cloud providers such as AWS, Azure, Google Cloud, and more. Each provider has its own set of resources and configuration options.
- **Resource**: A resource represents a specific infrastructure object that Terraform manages, such as virtual machines, storage buckets, networks, or DNS records. Resources are defined within Terraform configuration files and are created, updated, or destroyed based on the desired state specified in the configuration.
Module: A module is a reusable component in Terraform that encapsulates a set of resources and their configurations. Modules allow for the abstraction and organization of infrastructure configurations, enabling code reusability, modularity, and easier management of complex infrastructure deployments.
- **State**: The state in Terraform refers to a file that keeps track of the current state of the infrastructure managed by Terraform. It contains information about the resources Terraform manages, such as their IDs, properties, and relationships. The state file is used to track changes and perform updates, and it is critical for ensuring consistency and managing infrastructure over time.
- **Variables**: Variables are used to define and parameterize Terraform configurations. They allow for the dynamic input of values, making configurations reusable and customizable. Variables can be defined at different levels, including in the root module, child modules, or passed through the command line.
- **Output**: Outputs in Terraform allow for the export of information from the infrastructure after it has been created or updated. Outputs can include IP addresses, resource IDs, or any other relevant data. They are useful for sharing information between different modules or for providing valuable outputs to users.
- **Backend**: The backend in Terraform determines where the state file is stored. It can be a local file, a remote storage system like Amazon S3 or Azure Blob Storage, or a collaboration service like Terraform Cloud. The backend configuration defines how state is managed and accessed, providing a centralized location for team collaboration and state storage.
- **Plan**: A plan in Terraform is the result of running the terraform plan command. It provides a preview of the changes that will be made to the infrastructure based on the current configuration and the desired state. The plan shows what resources will be created, updated, or destroyed, allowing for review and validation before applying the changes.
- **Apply**: Applying in Terraform refers to the process of making changes to the infrastructure based on the desired state defined in the configuration. When running the terraform apply command, Terraform creates, updates, or destroys resources to match the desired state, ensuring the infrastructure reflects the configuration specifications.
- **Destroy**: Destroying in Terraform is the process of removing all resources managed by Terraform. When running the terraform destroy command, Terraform reads the state file and deletes all resources it manages, effectively destroying the infrastructure created by Terraform.

### Terraform the Workflow:
The workflow of Terraform involves several steps, starting from initialization and progressing through planning, resource provisioning, and, finally, applying the changes. Let's walk through each step in the Terraform workflow:

1. **Initialization**: The first step is to initialize a Terraform project within a directory containing Terraform configuration files. By running the command terraform init, Terraform downloads the necessary provider plugins and sets up the backend for storing the state file. Initialization ensures that Terraform has the required dependencies and is ready to manage the infrastructure.
2. **Configuration**: After initialization, you define the desired infrastructure configuration using Terraform's declarative language (HCL - HashiCorp Configuration Language). Configuration files typically have a .tf extension and specify the resources, variables, and other settings required for your infrastructure.
3. **Planning**: Once the configuration is defined, you can run terraform plan. Terraform analyzes the configuration and compares it against the current state recorded in the state file. The planning phase determines the changes needed to achieve the desired state, such as creating, updating, or destroying resources. The plan output provides a detailed overview of the proposed changes without actually modifying the infrastructure.
4. **Resource Provisioning**: After reviewing the plan and ensuring it reflects your intentions, you can apply the changes by running terraform apply. Terraform reads the configuration, determines the necessary actions, and communicates with the respective cloud provider API(s) to provision or modify resources accordingly. Terraform will prompt for confirmation before making any modifications.
5. **State Management**: Terraform keeps track of the state of the infrastructure it manages. The state file (by default named terraform.tfstate) is created during the initial terraform apply and is updated with each subsequent apply. It stores metadata about resources, such as their IDs, attributes, and dependencies. The state file is crucial for Terraform to understand the existing infrastructure and track changes over time.
6. **Updating Infrastructure**: As your infrastructure requirements change, you can update the Terraform configuration files. Running terraform plan again will identify the necessary modifications based on the changes in the configuration. Applying the changes using terraform apply will then update the infrastructure to match the modified configuration.

Throughout this workflow, Terraform maintains the desired state of the infrastructure based on the configuration files and handles the necessary interactions with the cloud provider APIs. It ensures that the infrastructure is provisioned, updated, and scaled according to the desired configuration while managing the dependencies and relationships between resources.

### Conclusion:

In this article, we explored the Terraform, its workflow and how it simplifies infrastructure management through its declarative approach. We discussed the initialization process, configuration definition, planning phase, resource provisioning, and state management. By following this workflow, organizations can achieve consistent and automated infrastructure deployments while leveraging the power of Infrastructure as Code.