Advanced CLI: import, logging, and debugging

# Full example: importing an existing VPC

# Step 1: Get the VPC ID from AWS
# aws ec2 describe-vpcs --query 'Vpcs[?Tags[?Key==`Name`&&Value==`legacy-vpc`]].VpcId'
# Output: "vpc-0abc123def456"

# Step 2: Create the resource block (minimum required)
# main.tf:
resource "aws_vpc" "legacy" {
  cidr_block = "172.16.0.0/16"  # real value — get it from the console
}

# Step 3: Import
terraform import aws_vpc.legacy vpc-0abc123def456

# Step 4: View the plan
terraform plan
# ~ aws_vpc.legacy  (modify because attributes are missing)

# Step 5: Update the code with all the attributes
resource "aws_vpc" "legacy" {
  cidr_block           = "172.16.0.0/16"
  enable_dns_support   = true     # adjust according to the plan
  enable_dns_hostnames = true
  tags = {
    Name = "legacy-vpc"
  }
}

# Repeat plan until you see: "No changes. Your infrastructure matches the configuration."

# ALTERNATIVE: import block + generate-config (Terraform 1.5+)
import {
  to = aws_vpc.legacy
  id = "vpc-0abc123def456"
}

terraform plan -generate-config-out=vpc_legacy.tf  # automatically generates the resource block

# Enable logging in the current session
export TF_LOG=DEBUG
terraform plan

# Save logs to a file (without this, they go to stderr)
export TF_LOG=TRACE
export TF_LOG_PATH=/tmp/terraform-debug.log
terraform apply

# Separate Core and Provider logs (Terraform 0.15+)
export TF_LOG_CORE=INFO       # Terraform core logs
export TF_LOG_PROVIDER=DEBUG  # provider logs (calls to the AWS API, etc.)

# Disable logging
unset TF_LOG
# Or:
export TF_LOG=OFF

# Windows PowerShell:
$env:TF_LOG = "DEBUG"
$env:TF_LOG_PATH = "C:\temp\tf-debug.log"
terraform plan

# Typical error when the state is locked:
# Error acquiring the state lock: ConditionalCheckFailedException: ...
# Lock Info:
#   ID:        3a1c2fa8-b5d9-4f71-a3c7-123456789abc  ← this is the Lock ID
#   Path:      terraform.tfstate
#   Operation: OperationTypeApply
#   Who:       user@hostname
#   Version:   1.6.3
#   Created:   2024-01-15 10:23:45 UTC
#   Info:

# Release the lock with the ID shown in the error
terraform force-unlock 3a1c2fa8-b5d9-4f71-a3c7-123456789abc

# Confirm with -force (skips the interactive confirmation)
terraform force-unlock -force 3a1c2fa8-b5d9-4f71-a3c7-123456789abc

# Default value: 10 concurrent operations
terraform apply

# Increase parallelism (faster but more load on the API)
terraform apply -parallelism=20

# Reduce parallelism (useful if the cloud API has rate limiting)
terraform apply -parallelism=5

# The same flag works with plan and destroy
terraform plan -parallelism=15
terraform destroy -parallelism=5

# ⚠️ Increasing it too much can cause throttling errors on cloud APIs
# AWS, Azure, and GCP all have rate limits on their APIs