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quixoticmonk
quixoticmonk

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Managing Terraform State for AWS workloads with v1.10.0-beta1

#terraform #s3 #aws #hashicorp

When working with Terraform in a team environment or production setup, it's crucial to store the state file remotely and implement state locking. If you read up on the current documentation and any examples out there in the internet, you would find something similar to the notes below . Towards the second section of this article, you will see the change in the S3 backend configuration which is coming up in Terraform and how to do it.

Current implementation

AWS S3 provides reliable storage for the state file, while DynamoDB enables state locking to prevent concurrent modifications.

Current S3 Backend Configuration

To configure Terraform to use S3 and DynamoDB as a backend, add the following configuration to your Terraform files:

terraform {
  backend "s3" {
    bucket         = "tfstatebucket"
    key            = "locks/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-state-lock"
  }
}
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What is changing ?

As of Aug 20, 2024 Amazon S3 added support for conditional writes that can check for the existence of an object before creating it. This capability can help you more easily prevent applications from overwriting any existing objects when uploading data.

Lets break this down a bit. Imagine you and your colleague are both trying to save a document with the same name to a shared directory or S3 bucket.
Without conditional writes:

  • Both of you can save the file
  • Whoever saves last overwrites the other person's work
  • There's no built-in way to prevent this conflict

With conditional writes:

  • Before saving, S3 checks if a file with that name already exists
  • If it exists, S3 will reject the save operation
  • If it doesn't exist, the save operation proceeds

Now, why is this important with Terraform state ? Terraform State file as you know is the single most crucial element which helps Terraform understand the current infrastructure state and helps any subsequent operations know what to do when encountering a change in configuration. Currently with the backend configuration above shown, we use DynamoDb to lock that file down in case of multiple entities ( human, machine) trying to access or update the file. With the conditional writes feature, we can leverage S3's native capabilities and eliminate the need for an additional component like DynamoDb in your backend infrastructure.

More details on the changes here.

New S3 Backend configuration

Pre-requisites

Currently, you need to be on the beta version of v1.10 of Terraform to be able to leverage the changes in S3 backend configuration. This is still a beta and so I wouldn't recommend you perform these changes on your production infrastructure.

Configuration

Based on the documentation, you can remove thedynamodb_table attribute that you are used to and add the experimental attributeuse_lockfile and set it to true.

To enable S3 state locking, use the following optional argument:
 use_lockfile - (Optional, Experimental) Whether to use a lockfile for locking the state file. Defaults to false.

terraform {
  backend "s3" {
    bucket       = "tfstatebucket"
    key          = "locks/terraform.tfstate"
    region       = "us-east-1"
    encrypt      = true
    use_lockfile = true
  }
}
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Existing infrastructure

Lets take the case of existing infrastructure you have provisioned with S3/DynamoDb combination for State management.

terraform {
  backend "s3" {
    bucket         = "tfstatebucket"
    key            = "locks/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    dynamodb_table = "terraform-state-lock"
  }
}
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Let's take these step by step.
Let's reconfigure your terraform backend configuration to add the input use_lockfile = true.

terraform {
  backend "s3" {
    bucket         = "tfstatebucket"
    key            = "locks/terraform.tfstate"
    region         = "us-east-1"
    encrypt        = true
    use_lockfile   = true
    dynamodb_table = "terraform-state-lock"
  }
}
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On your next plan or apply, you will be prompted to reconfigure the backend.
│ Error: Backend initialization required: please run "terraform init"
│
│ Reason: Backend configuration block has changed
│
│ The "backend" is the interface that Terraform uses to store state,
│ perform operations, etc. If this message is showing up, it means that the
│ Terraform configuration you're using is using a custom configuration for
│ the Terraform backend.
│
│ Changes to backend configurations require reinitialization. This allows
│ Terraform to set up the new configuration, copy existing state, etc. Please run
│ "terraform init" with either the "-reconfigure" or "-migrate-state" flags to
│ use the current configuration.
│
│ If the change reason above is incorrect, please verify your configuration
│ hasn't changed and try again. At this point, no changes to your existing
│ configuration or state have been made.
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  • Run the command terraform init -reconfigure 
Initializing the backend…
Successfully configured the backend "s3"! Terraform will automatically
use this backend unless the backend configuration changes.
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  • Run terraform apply . If you are able to check your S3 bucket and DynamoDb table you would see these additional lock metadata added.
    • Info under DynamoDb which looks like below. 
{
    "ID": "d8590779-bcf6–728e-9897–4ba20e60b5e1",
    "Operation": "OperationTypeApply",
    "Info": "",
    "Who": "manu@xyz.com",
    "Version": "1.10.0",
    "Created": "2024–11–09T19:03:41.666663Z",
    "Path": "tfstatebucket/locks/terraform.tfstate"
}
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  • terraform.tfstate.tflock file which has the same information adjacent to your terraform.tfstate file in the S3 bucket for the time a plan or apply ( or destroy which is also an apply) is being performed. 
If you have multiple entities trying to acquire the lock at the same time, it continues to behave as you expect it to:
│ Error: Error acquiring the state lock
│
│ Error message: operation error S3: PutObject, https response error StatusCode: 412,
│ RequestID: SEJ4FAEDKAZ36XCP, HostID:
│ w4VEpne8lEszQmPW98EI13suUuK7iJqMKN1mE3mQKvO0i94SyzI8AjThWNN1r0HkOkfNO7Y6S2Y=, api
│ error PreconditionFailed: At least one of the pre-conditions you specified did not
│ hold
│ Lock Info:
│ ID: 6568a719–6919-ffb7-f5ec-a2791ad9805a
│ Path: tfstatebucket/locks/terraform.tfstate
│ Operation: OperationTypeApply
│ Who: manu@xyz.com
│ Version: 1.10.0
│ Created: 2024–11–09 19:07:46.1006 +0000 UTC
│ Info:
│
│
│ Terraform acquires a state lock to protect the state from being written
│ by multiple users at the same time. Please resolve the issue above and try
│ again. For most commands, you can disable locking with the "-lock=false"
│ flag, but this is not recommended.
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Removing the DynamoDb input

With the use_lockfile flag and DynamoDb table specified, you have both DynamoDb and S3 handling those references of the digest and lock for the time being. This will be supported initially in the v1.10.0 of terraform from the changelog.

At this point you are free to remove the dynamoDb table reference from the backend configuration. From the changelog,

When used with DynamoDB-based locking, locks will be acquired from both sources. In a future minor release of Terraform the DynamoDB locking mechanism and associated arguments will be deprecated.

It is expected to have the dynamoDB requirements be removed in a later version of terraform binary. At this point this should behave similar to the new backend configuration below. Remember to perform a terraform init -reconfigure as after removing DynamoDb table input.

terraform {
  backend "s3" {
    bucket       = "tfstatebucket"
    key          = "locks/terraform.tfstate"
    region       = "us-east-1"
    encrypt      = true
    use_lockfile = true
  }
}
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  • Run terraform apply. You should see that the S3 bucket continues to function with the tflock file for the time apply is being processed.

If you add a small change to you configuration and perform a terraform apply, you can verify that the digest stored in DynamoDb from the earlier run is no longer updated.

Provisioning New Infrastructure

I do not recommend doing this currently for production infrastructure ( till v1.10.0 is published or even further based on your organizations tolerance levels). But if you are testing the beta version, all you need is to provide a backend configuration as below and run your terraform workflow. You have one less infrastructure component to manage to manage your state.

terraform {
  backend "s3" {
    bucket       = "tfstatebucket"
    key          = "path/to/terraform.tfstate"
    region       = "us-east-1"
    encrypt      = true
    use_lockfile = true
  }
}
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Conclusion

For teams using Amazon S3/DynamoDb combination to manage their Terraform state, this is a big step in reducing the backend configuration to have just one component ( S3) going forward. Give it a try and let me know if you had any issues with this.

References:

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