7 Terraform Logging

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🔵 Terraform Diff Symbols (VERY IMPORTANT)

Terraform shows diffs like this:

+ create
~ update in-place
- destroy
-/+ replace
<= read (data source)

Let’s break them down:

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✔ + Create

Terraform will create a resource.

Example:

# aws_lambda_function.put will be created
+ resource "aws_lambda_function" "put" {

Meaning:
Resource does NOT exist in AWS → Terraform will create it.

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✔ ~ Update In-Place

Resource exists but needs modification.

~ memory_size: 128 → 256

Meaning:
Terraform will update the resource without deleting it.

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✔ - Destroy

Terraform will delete a resource.

- resource "aws_lambda_function" "old"

Meaning:
Terraform thinks this resource should not exist.

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✔ -/+ Replace

Resource must be destroyed then recreated.

-/+ resource "aws_lambda_function" "example"

Meaning:
Some attributes force replacement, like:

• function name

Terraform will:
1️⃣ destroy
2️⃣ recreate

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✔ <= Read

This is for data sources.

<= data "aws_ami" "latest"

Meaning:
Terraform is reading data (not creating anything).

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🟧 Plan Summary (bottom section)

At the bottom of terraform plan, you always see:

Plan: 3 to add, 1 to change, 0 to destroy

This is your quick summary.

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🔵Terraform Logs (TF_LOG)

Terraform has internal debug logs beyond CLI output.

You enable them using environment variables:

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🔥 Debug Levels

TF_LOG=ERROR
TF_LOG=WARN
TF_LOG=INFO
TF_LOG=DEBUG
TF_LOG=TRACE

Example:

export TF_LOG=DEBUG
terraform plan

Meaning:

• ERROR = only fatal failures
• WARN = warnings
• INFO = lifecycle messages
• DEBUG = provider communication details
• TRACE = very deep details (API requests, JSON, diff engine)

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📁 3️⃣ TF_LOG_PATH — Save logs to a file

Instead of printing to terminal:

export TF_LOG=DEBUG
export TF_LOG_PATH="terraform.log"
 
terraform apply

Now all logs go into:

terraform.log

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