Terraform_remote_state usage - Step-by-Step Execution

Process Flow - Terraform_remote_state usage

Define remote state backend

↓

Configure remote state data source

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Terraform init to connect backend

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Terraform apply to read remote state

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Use remote state outputs in current config

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Deploy infrastructure with shared data

Terraform remote state usage involves configuring a backend to store state, then accessing that state from another configuration to share data.

Execution Sample

Terraform

terraform {
  backend "s3" {
    bucket = "my-tf-state"
    key    = "app/terraform.tfstate"
    region = "us-east-1"
  }
}
data "terraform_remote_state" "network" {
  backend = "s3"
  config = {
    bucket = "my-tf-state"
    key    = "network/terraform.tfstate"
    region = "us-east-1"
  }
}
output "vpc_id" {
  value = data.terraform_remote_state.network.outputs.vpc_id
}

This code configures an S3 backend for remote state and accesses outputs from a remote state named 'network'.

Process Table

Step	Action	Terraform Command	State Accessed	Result
1	Define backend in terraform block	terraform init	No previous state	Backend configured to S3 bucket
2	Initialize terraform with backend	terraform init	No previous state	Backend connection established
3	Apply network config to create resources	terraform apply	Remote state created	Network resources created, state saved remotely
4	Configure terraform_remote_state data source	terraform plan	Reads remote state from S3	Remote outputs available for use
5	Use remote outputs in current config	terraform apply	Reads remote state	Current config uses remote VPC ID
6	Deploy current infrastructure	terraform apply	Remote state accessed	Resources created using remote state data
7	End	-	-	Execution complete, remote state shared successfully

💡 Terraform completes apply after accessing remote state outputs successfully.

Status Tracker

Variable	Start	After Step 3	After Step 5	Final
backend_configured	false	true	true	true
remote_state_accessible	false	false	true	true
vpc_id	null	set in remote state	read from remote state	used in current config

Key Moments - 3 Insights

Why do we run 'terraform init' before accessing remote state?

Because 'terraform init' sets up the backend connection, allowing Terraform to read or write remote state as shown in execution_table step 2.

How does Terraform know where to find the remote state?

The remote state data source is configured with backend details (bucket, key, region), so Terraform reads the state from that location as in step 4.

What happens if the remote state is not accessible during 'terraform apply'?

Terraform will fail to read required outputs, causing the apply to error out, since it depends on remote state data as in step 5.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does Terraform first access the remote state outputs?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Check the 'State Accessed' column in execution_table rows for when remote state is read.

According to variable_tracker, when does 'remote_state_accessible' become true?

A After Step 3

B At Start

C After Step 5

D Never

💡 Hint

Look at the 'remote_state_accessible' row in variable_tracker to see when it changes.

If the backend configuration was missing, what would happen at Step 2?

A Terraform init would succeed without backend

B Terraform init would fail to connect backend

C Terraform apply would create resources anyway

D Remote state would be accessible

💡 Hint

Refer to execution_table Step 2 where backend connection is established.

Concept Snapshot

Terraform remote state usage:
- Configure backend in terraform block (e.g., S3 bucket)
- Run 'terraform init' to set backend
- Use 'terraform_remote_state' data source to read outputs
- Access remote outputs as variables
- Enables sharing state between configs
- Must ensure backend is accessible before apply

Full Transcript

Terraform remote state usage involves setting up a backend to store the state file remotely, such as in an S3 bucket. First, you define the backend configuration in the terraform block and run 'terraform init' to initialize the backend connection. Then, after applying the initial configuration to create resources and save state remotely, you configure a terraform_remote_state data source in another configuration to read outputs from that remote state. This allows sharing data like VPC IDs between different Terraform projects. The process requires the backend to be accessible during 'terraform apply' to successfully read remote outputs and deploy dependent resources.