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Create Atlantis with ECS Fargate for automation provisioning

Sep 29, 2024, 16 min read

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Hi @all, this week is so busy for me, and this about to learn something new about gitops and techniques and tools depend on this concept, and this week I will take a break kubewekend series. Therefore, today we will learn about atlantis - gitops for automatic provisioning your infrastructure. Let’s digest !!

What is Atlantis ?

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Infrastructure as Code is becoming the importance part of DevOps role model, It means DevOps engineer can resolve many problem to help am I swallow all technically inside cloud and that is possible. Terraform, Pulumi, Chef, OpenTofu - Those come up and make this game to become more easier than ever, really tough !!! And we always have next-question about How can we create automation with those ? Does any things can help us ?

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And the answer is yes, and that is a lot solutions to help you attack problem, such as

  • Basic method, you choose one of code management platform, and implement the process CI/CD with one of IaC which related above to help you provisioning and managing your infrastructure
  • Advantage method, you choose GitOps which same idea as basic methodology but extend on the process about you only use Pull Request to control everything your infrastructure and deployment

It seem like not a big deal, you can choose what ever you want if you feel great with right expectation. You can read more about different between GitOps and Traditional CI/CD below

But as you know, I want to try and hand on with another tools, another concept and see what is big difference between of them and figure out what things need to clarify when you choose GitOps or CI/CD for your projects

And I will try with Infrastructure as first, and IaC is first topic I relate to GitOps. So with IaC, you have multiple platform to hand on and one of most popular is Atlantis. You can choose alternative at Alternative Atlantis

Introduce

You can find more information about Atlantis in the documentation and github

Info

Atlantis

Atlantis is a tool for collaborating on Terraform. The core functionality of Atlantis enables developers and operators to run terraform plan and apply directly from Terraform pull requests. Atlantis then comments back on the pull request with the output of the commands

You can image when you open PR, Atlantis will act like bot who will help you run plan inside Terraform workflow, and send back your output inside comment. You can directly communicate with Atlantis to making changes inside your Infrastructure with no effort

And depend on that idea, your team will receive the massive efficiency in

  • Collaboration: You can analysis what change inside your PR where your team can easily see and feedback to give best decision before all of changes merge to master branch for example
  • Help Developers Writing Terraform : It means you create environment where developer doesn’t have credentials can be accessed, and help devloper can change infrastructure in plan state where Ops team apply when you give same agreement

That why you need Atlantis right now for your project 😄, be external Atlantis will also ensure you about

  • Make Fewer mistake
  • Instant Audit Logs
  • Self-hosted
  • Open Source

Assemble all of things, Atlantis is becoming potential to choosing when you want create GitOps process inside your project, easily and powerful. But you can consider to choose another one because out there are also equally good products

  • scalr :  Remote operations backend for Terraform and OpenTofu (OTF)
  • digger : open-source CI/CD orchestrator for Terraform
  • env0:  best way to automate and manage any Infrastructure-as-Code, from Terraform and OpenTofu to Pulumi, CloudFormation, Terragrunt, Kubernetes, and more.

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Lastly, Tool is not important, but if you know more than one you can push yourself to higher level, improve your mindset and do lot of useful things. Atlantis and what ever, It depends on your choosing. Good luck BTW 😄😄😄

How can Atlantis work

Like I relate above, Atlantis is opensource and you can understand all of concept or strategy inside their source code

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You can try self-hosted Atlantis in the multiple way, including

If you choose self-hosted locally, ensure your host

  • Install terraform or opentofu in your host (Binaries)
  • Use ngrok or localtunnel to expose your Atlantis to your repositories, with actual URL. IDK does raw IP can be used but ensure use URL with SSL to except problems. Troubleshoot HTTPS, SSL, TLS

Take a look Atlantis workflow, really simple

  • First, when you create PR with code change, your repositories create trigger to webhook which set for Atlantis
  • Atlantis will listen the trigger, after receiving the triggers they will pull the source code and use the algorithm inside autoplanning to run plan before return result to PR as comment
  • If you looks good output plan send from Atlantis inside PR, you can try interact with Atlantis to continue check or use apply function to apply change into Cloud
  • When Atlantis receive the apply, It will run apply to your cloud with your code and set it up to AWS or what ever. If something wrong, Atlantis will return message error and unless completely anything output plan, your PR will be closed by Atlantis via automerging

With workflow like above, when create Atlantis for yourself, ensure create

Currently, Atlantis is supporting for multiple code management tool, choose one of them and let try to self-hosted

I will choose Gitlab for guiding you what exactly need to setup your webhook and cred

Create Gitlab Account and configuration for Atlantis

Following the requirement, you can create gitlab user is atlantis or use own account, anything is fine, sometimes you just need to do some basically

To create cred of your gitlab, It is actually PAT (Personal Access Token), you can following this tutorial to create for your one. Base on Atlantis, you need create Token assigned scope API, remember record that value to use on next part

Info

Your token can have format glpat-xxxxxxxxxxxxxx

Next you just need to create webhook, but currently you don’t have target URL make sure you update that after your Atlantis work. Explore more by following Atlantis

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Choose Webhooks and put the information with secrets you prepare

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And now select option webhook can effect with your PR

  • Push events
  • Comments
  • Merge request events

Now you have all of things to setup Atlantis for yourself. Reach to Terraform code to know how to provisioning that one inside AWS Fargate

Provisioning Atlantis

Info

Following the documentation from Atlantis, we can choose Fargate of AWS to operating our container Atlantis. If you know, Fargate is belong to service of AWS called ECS (Elastic Container Service) which one use to deploy and operate container via task or docker-compose, really tough

Some feature of ECS which I related on Fastway to deploy your application with AWS and you can do it all with your code using module at AWS Atlantis

To understand more about ECS and Fargate, I will follow to create all services by manual and provide that for Atlantis module, mostly about networking, As you come from Azure and newbie in AWS you will surprise with AWS networking concept

Create and learn about networking with AWS

Base on AWS, ever you hear about Public Subnet, that concept is unique because when you learn about networking in General, you just have Private Subnet and that all. Now we must use both of them Public and Private inside AWS and that can be tough thing but very pleasant

When I follow this article ECS (Fargate) with ALB Deployment Using Terraform, I have open view to implement what you need inside networking when try create your own in AWS

Note

In conclusion, AWS have NAT gateway (In Azure it not need to use) but in AWS you need this to go to the Internet, if not your host will work only from inbound site and not egress your outbound 😄, and in the other way you need to use Internet Gateway to through ALB before hit to your Application

Now we will do self-provisioning that, nowadays AWS is spending the module to help cut off the work to handle networking, you can check at AWS VPC

Create your networks.tf and applied this code below

networks.tf
# Networking
data "aws_availability_zones" "default" {
}
 
resource "aws_vpc" "atlantis" {
  cidr_block = var.vpc_cidr
  tags       = var.tags
}
 
resource "aws_internet_gateway" "atlantis" {
  vpc_id = aws_vpc.atlantis.id
  tags   = var.tags
}
resource "aws_eip" "atlantis" {
  domain = "vpc"
  tags   = var.tags
}
 
resource "aws_nat_gateway" "atlantis" {
  allocation_id = aws_eip.atlantis.id
  subnet_id     = aws_subnet.public_atlantis[0].id
  tags          = var.tags
  depends_on    = [aws_internet_gateway.atlantis]
}
 
# Private subnet
resource "aws_subnet" "private_atlantis" {
  # Why: ALB need at least two subnets in different regions
  count             = 3
  vpc_id            = aws_vpc.atlantis.id
  cidr_block        = "10.0.${count.index}.0/24"
  availability_zone = data.aws_availability_zones.default.names[count.index]
  tags              = var.tags
  lifecycle {
    create_before_destroy = true
  }
}
 
resource "aws_route_table" "private_atlantis" {
  vpc_id = aws_vpc.atlantis.id
  tags   = var.tags
}
 
resource "aws_route" "private_atlantis" {
  route_table_id         = aws_route_table.private_atlantis.id
  destination_cidr_block = "0.0.0.0/0"
  nat_gateway_id         = aws_nat_gateway.atlantis.id
}
 
resource "aws_route_table_association" "private_atlantis" {
  count          = 3
  subnet_id      = aws_subnet.private_atlantis[count.index].id
  route_table_id = aws_route_table.private_atlantis.id
 
  depends_on = [aws_route_table.private_atlantis]
}
 
# Public subnet
resource "aws_route_table" "public_atlantis" {
  vpc_id = aws_vpc.atlantis.id
  tags   = var.tags
}
resource "aws_subnet" "public_atlantis" {
  count             = 3
  vpc_id            = aws_vpc.atlantis.id
  cidr_block        = "10.0.${count.index + 3}.0/24"
  availability_zone = data.aws_availability_zones.default.names[count.index]
  tags              = var.tags
  lifecycle {
    create_before_destroy = true
  }
}
 
resource "aws_route" "public" {
  route_table_id         = aws_route_table.public_atlantis.id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.atlantis.id
}
 
resource "aws_route_table_association" "public" {
  count          = 3
  subnet_id      = aws_subnet.public_atlantis[count.index].id
  route_table_id = aws_route_table.public_atlantis.id
  depends_on     = [aws_route_table.public_atlantis]
}
variables.tf
### General
variable "tags" {
 
  type = object({
    provision = string,
    domain    = string,
    used_by   = string,
    account   = string
  })
  description = "Tags for module which this one provisioned"
  default = {
    provision = "terraform",
    domain    = "cicd",
    used_by   = "atlantis",
    account   = "infrastructure"
  }
}
 
variable "region" {
  type        = string
  default     = "ap-southeast-1"
  description = "Region for provisioning module"
}
 
### Network
variable "vpc_cidr" {
  type        = string
  default     = "10.0.0.0/16"
  description = "The IPv4 CIDR block for the VPC"
}

As you can see, the code will create inside VPC to 6 subnet, half of them spend for Private and other spend for Public, you can image

  • Create VPC at range 10.0.0.0/16 will include 65536 network

  • The AWS ALB need create at least 2 subnet in different zone, therefore I create 3 subnet in 3 different zone base on data.aws_availability_zones.default with return 3 zone a b c

  • Attach zone and create 3 subnet for private and 3 subnet for public, It will

    • Public subnet: 10.0.3.0/24 10.0.4.0/24 and 10.0.5.0/24 in ap-southeast-1a to ap-southeast-1c
    • Private subnet: 10.0.0.0/24 10.0.1.0/24 and 10.0.2.0/24 in ap-southeast-1a to ap-southeast-1c

  • Create Nat Gateway and Internet Gateway, and two Route Table to create connection between subnet with these Gateway

  • Create the association between Nat Gateway with Private Network at range 0.0.0.0/0 and Internet Gateway with Public Network at range 0.0.0.0/0

Now you already provisioning network for your ALB and It means you can attach network with ALB and use that assign to ECS where can load traffic

Warning

If you misconfiguration, that all kind reason in AWS start from networking. You need to verify at all and adapt right concept of AWS. Hope so 0 error in your provisioning progress

Apply the workflow of Terraform to get your result, remember set the backend of aws or what ever you want to, check out about Backends Configuration

# Init
terraform init # Use -reconfigure if you change your backend
 
# Plan
terraform plan
 
# Apply
terraform apply

Now access in your AWS, view in VPC service you will see

And that do same as connect like I describe with NAT and Internet Gateway, with route table 0.0.0.0/0 for allow all traffic to and out VPC

Use Network for Atlantsis module

If you provisioning all of them, your other work will very simple because module will take care and create all of part, you need to concern how set right configuration for Atlantis and give network subnet for right location

atlantis.tf
locals {
  service_subnets      = [for s in aws_subnet.private_atlantis : s.id]
  alb_subnets          = [for s in aws_subnet.public_atlantis : s.id]
  # Put your gitlab-user with non @ who you created PAT Token
  atlantis_gitlab_user = "xeus.nguyen"
  root_domain          = "xeusnguyen.xyz"
}
 
data "aws_route53_zone" "infrastructure" {
  name         = "infrastructure.${local.root_domain}"
  private_zone = false
}
data "aws_acm_certificate" "infrastructure" {
  domain   = "*.infrastructure.${local.root_domain}"
  statuses = ["ISSUED"]
}
 
module "atlantis" {
  source  = "terraform-aws-modules/atlantis/aws"
  version = "4.4.0"
 
  name = "atlantis"
 
  # ECS Container Definition
  atlantis = {
    environment = [
      {
	    # GitLab username of API user
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#gitlab-user
        name  = "ATLANTIS_GITLAB_USER"
        value = local.atlantis_gitlab_user
      },
      {
	    # Provide the allowlist repostories to connected with Atlantis
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#repo-allowlist
        name  = "ATLANTIS_REPO_ALLOWLIST"
        value = "gitlab.com/allow-list/*"
      },
      {
	    # Username used for Basic Authentication on the Atlantis web service. Defaults to `atlantis`.
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#web-username
        name  = "ATLANTIS_WEB_USERNAME"
        value = "atlantis"
      },
      {
	    # Enable Basic Authentication on the Atlantis web service.
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#web-basic-auth
        name  = "ATLANTIS_WEB_BASIC_AUTH"
        value = "true"
      },
      {
	    # Automatically merge pull requests after all plans have been successfully applied. Defaults to `false`
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#automerge
        name  = "ATLANTIS_AUTOMERGE"
        value = "true"
      }
    ]
    secrets = [
      {
	    # GitLab token of API user.
	    # Documnetation: https://www.runatlantis.io/docs/server-configuration#gitlab-token
        name      = "ATLANTIS_GITLAB_TOKEN"
        valueFrom = "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_gitlab_token:value:AWSCURRENT:"
      },
      {
	    # Secret used to validate GitLab webhooks.
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#gitlab-webhook-secret
        name      = "ATLANTIS_GITLAB_WEBHOOK_SECRET"
        valueFrom = "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_gitlab_webhook_secret:value:AWSCURRENT:"
      },
      {
	    # Password used for Basic Authentication on the Atlantis web service. Defaults to `atlantis`.
	    # Documentation: https://www.runatlantis.io/docs/server-configuration#web-password
        name      = "ATLANTIS_WEB_PASSWORD"
        valueFrom = "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_web_password:value:AWSCURRENT:"
      }
    ]
  }
 
  # ECS Service
  service = {
	# ARN to give permission your ECS can access
    task_exec_secret_arns = [
      "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_gitlab_token",
      "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_gitlab_webhook_secret",
      "arn:aws:secretsmanager:ap-southeast-1:xxxxxxx:secret:atlantis_web_password"
    ]
    # Provide Atlantis permission necessary to create/destroy resources
    tasks_iam_role_policies = {
      AdministratorAccess = "arn:aws:iam::aws:policy/AdministratorAccess"
    }
  }
  service_subnets = local.service_subnets
  vpc_id          = aws_vpc.atlantis.id
 
  # ALB
  alb_subnets             = local.alb_subnets
  create_certificate      = false
  create_route53_records  = false
  certificate_arn         = data.aws_acm_certificate.infrastructure.arn
  certificate_domain_name = "atlantis.infrastructure.${local.root_domain}"
  route53_zone_id         = data.aws_route53_zone.infrastructure.zone_id
  tags                    = var.tags
 
  depends_on = [aws_subnet.private_atlantis, aws_subnet.public_atlantis]
}
 
resource "aws_route53_record" "atlantis" {
  zone_id = data.aws_route53_zone.infrastructure.zone_id
  name    = "atlantis.infrastructure.${local.root_domain}"
  type    = "CNAME"
  ttl     = 300
  records = [split("https://", module.atlantis.url)[1]]
}

As you can see, that module is really long, and you need to ensure provide enough parameter before applied, there are two thing you need concern inside this code

If you control everything is work, apply terraform workflow go live your Atlantis with AWS Fargate

Now access the URL which bind via CNAME of Route53 and get access to Atlantis Web

Add some specific configuration for Atlantis (Update)

To manipulate your Atlantis can retrieve any module from remote registry, such as GitLab, Terraform Cloud, … This platform releases for us the method through environment variable, including

  • —tfe-hostname: Hostname of your Terraform Enterprise installation to be used in conjunction. e.g: gitlab.com, but with default: app.terraform.io
  • —tfe-token: A token for Terraform Cloud/Terraform Enterprise integration. e.g: glpat-xxxxxx or secret-manager:xxxxx

Explore more about this configuration through article Atlantis - Terraform Cloud/Enterprise

Info

If you know you know, Terraform offer us some methods to configuration that one, but you need to hand on with manually. Read more at: CLI Configuration File (.terraformrc or terraform.rc)

For example:

~/.terraformrc
credentials "gitlab.com" {
  token = "glpat-xxxxxxxxx"
}

How Webhook work with Atlantis

Now we update webhook configuration in URL to your actually URL of Atlantis, try click test and you will see HTTP 200 and that one really good, now you can use Atlantis in your Gitlab

When you create PR, you can see your bot or user which you set up in Server Configuration of Atlantis will response plan like this

As you can see, Atlantis run plan in root directory, it means that find right path base on algorithm which I want

Externally, You can continue with Atlantis using comment with trigger webhook

  • If you want to specific plan path, use -d child/path to select exactly location what you want. Read more at atlantis plan
  • If your plan return expectation result, send comment atlantis apply to trigger apply, after finished with not problem Atlantis will auto close your PR. Read more at atlantis apply
  • If you want to destroy, you can use -destroy flag, with plan command. Read more at Using the -destroy Flag
  • You have same command like Terraform, like import to import module you want to currently plan. Read more at atlantis import
  • You can relate with another command atlantis state rm, atlantis unlock and atlantis approve_policies

With advantage feature of Atlantis, you can do more stuff to attack with customize deep inside this one

Conclusion

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Success

That all for today, hope you find well with Atlantis and figure out what you need to do for setup Atlantis for yourself. AWS is come up with new idea and concept that why I need to catch up and feel free share that for you, happiness to do that. DM me if you meet any problems in setup Atlantis, I will feel free to take a seat and response LOL 😄

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This week is not bad, learn something new and give my brain chill and recovery after Kubewekend , so if I not busy much, Kubewekend will return on the next weekend, one time again I really appreciate what your diligent to spend your time for reading my blog, therefore take care your health, stay safe, learn something new and I will see you on next week, bye bye 😄

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