Day 11 - Infrastructure as Code | Terraform

1. Scenario: You Are a DevOps Engineer at Flipkart

Flipkart has many applications (example: 300 apps).
To run these applications, servers are required.
These servers (compute resources like CPU, RAM, storage) can be created:

• On cloud platforms (AWS, Azure, GCP, etc.)

• On physical machines (on-premises)

• On other cloud providers like DigitalOcean, Oracle Cloud, etc.

You decide to host everything on AWS.
So you automate the creation of resources like EC2, S3, RDS using:

• AWS CLI

• CloudFormation Templates (CFT)

• AWS CDK

• Other AWS automation tools

You create hundreds of scripts using CloudFormation (CFT) to automate AWS resources.
Everything works smoothly.

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2. The Problem: Cloud Provider Migration

Later, management decides to move from AWS to Azure.
Your existing CFT scripts become useless because:

• CloudFormation works only for AWS.

On Azure, you now have to rewrite everything using:

• Azure Resource Manager (ARM templates)

So you again convert all scripts manually.

After some time, the company is unhappy with Azure too and decides to move to on-premises using:

• OpenStack

OpenStack uses Heat Templates, so again you must rewrite all automation scripts.

This is a repeating problem:

✔ Every cloud provider has its own IaC syntax
✔ You keep rewriting scripts again and again
✔ It wastes time, effort, and learning resources

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3. Hybrid Cloud Makes Things Worse

Nowadays, many companies use Hybrid Cloud, meaning:

• Some infrastructure in AWS

• Some in Azure

• Some on-prem with OpenStack

• Sometimes even GCP or others

Example:

• AWS is good for storage

• Azure is good for DevOps services

So Flipkart uses both.

This forces a DevOps engineer to learn:

• AWS CFT

• Azure ARM

• OpenStack Heat Templates

• Many other provider-specific tools

This becomes too complicated.

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4. Solution: Terraform

To solve this multi-tool problem, HashiCorp created Terraform.

Terraform says:

“Instead of learning dozens of tools, learn just one — Terraform.”

Terraform Features:

• Works with all cloud providers (AWS, Azure, GCP, OpenStack…)

• You write one type of script (HCL) for all providers

• Terraform internally communicates with the provider’s API

• Migration from one cloud to another becomes much easier
  (only small changes like provider block / module updates)

Terraform uses the concept:

API as Code

Earlier tools were:

• CFT → AWS-specific

• ARM → Azure-specific

• Heat → OpenStack-specific

But Terraform works across all providers because:

Terraform converts your code → cloud provider API calls

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5. What Terraform Does Internally

Each cloud has APIs:

• AWS APIs

• Azure APIs

• GCP APIs

• OpenStack APIs

Terraform reads your .tf scripts and:

1. Converts them into correct API calls

2. Sends those calls to providers

3. Creates or updates the infrastructure

4. Shows results back to you

So you don’t need to write API requests yourself.

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6. Understanding API (Simple Explanation)

API = Application Programming Interface

It allows one application to talk to another programmatically.

Example:

• Normally, you open Google in a browser and search manually (UI).

• But if you want to talk to Google using a script, you use an API.

Similarly:

• Instead of manually creating cloud resources in a console,
  Terraform talks to cloud APIs and does it automatically.

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7. Summary

Infrastructure as Code (IaC)

• Writing infrastructure using scripts (CFT, ARM, Heat)

API as Code

• Terraform talking directly to cloud APIs

• One language, multiple cloud providers

Terraform solves the problem of learning many IaC tools.