Documentation as Code for Cloud - PlantUML

Basics

I've become a huge fan of PlantUML even before I came across the concept of "documentation as code" ¹ and it instantly won me over with its capabilities. I have used it in many different roles (software engineer, security engineer, security architect) extensively to draw diagrams (components, sequences) and mind maps.

Though initially, the general syntax might seem a bit challenging to understand, I believe that with some dedication, the learning curve becomes quite manageable. The reward of mastering PlantUML is well worth the effort, as it empowers you to create visually engaging and informative diagrams seamlessly.

One aspect where PlantUML might fall short is its default styling, which may not be as visually impressive as some other tools. However, this drawback can easily be overcome by incorporating icons and leveraging different themes to breathe life into your diagrams ² By doing so, you can elevate the aesthetic appeal and overall quality of your visual representations significantly by using standard icons (included withing the standard library) and 3rd-party ones .

Let's have a look how how a typical PlantUML document could look like:

<<styling options>> ❶

<<import of additional resources/modules>>  ❷
<<import of 3rd-party resources>>  ➌

<<resources>>  ❹

At the top of the document ❶ you define the basic layout of the resulting drawing (landscape mode, font size, font family, default direction in which resources should be created, etc.). Then you start adding different modules ❷ and ➌ which provide different entities and icons based on your needs. Finally you use your resources/entities, arrange them correspondingly and make relationships between them ❹.

This is what I'll use for the examples within this blog post ³:

' !define AWSPuml https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v16.0/dist
!define AWSPuml /home/victor/work/repos/aws-icons-for-plantuml/dist
!include AWSPuml/AWSCommon.puml
!include AWSPuml/AWSSimplified.puml
!include AWSPuml/ApplicationIntegration/APIGateway.puml
!include AWSPuml/ApplicationIntegration/SimpleNotificationService.puml
!include AWSPuml/ManagementGovernance/CloudWatch.puml
!include AWSPuml/Compute/EC2.puml
!include AWSPuml/Compute/EC2Instance.puml
!include AWSPuml/Compute/LambdaLambdaFunction.puml
!include AWSPuml/Groups/all.puml
!include AWSPuml/Containers/EKSCloud.puml
!include AWSPuml/Containers/ElasticKubernetesService.puml
!include AWSPuml/Containers/Containers.puml
!include AWSPuml/NetworkingContentDelivery/VPCNATGateway.puml
!include AWSPuml/NetworkingContentDelivery/VPCInternetGateway.puml
!include AWSPuml/NetworkingContentDelivery/VPCEndpoints.puml
!include AWSPuml/Storage/SimpleStorageService.puml
!include AWSPuml/SecurityIdentityCompliance/IAMIdentityCenter.puml

hide stereotype
skinparam linetype ortho

PlantUML is a powerful tool that goes beyond just creating basic diagrams; it also supports various types of grouped areas. These groupings play a crucial role in emphasizing the logical connections between different components or resources that belong to the same category, making it easier to understand complex systems.

When working with PlantUML, you have the flexibility to employ different types of groups to organize your diagrams effectively. Some of these groups include:

Groups

Let's have a look at the most common groups:

• Generic group

The most useful group (without any icons) is the generic group:

    GenericGroup(generic_group, "Generic Group") {
      package "Some Group" {
        HTTP - [First Component]
        [Another Component]
      }

      node "Other Groups" {
        FTP - [Second Component]
        [First Component] --> FTP
      }
    }

• Generic alt group

If you want to use another layout (without dotted lines) you could go for generic alt group:

    GenericAltGroup(generic_alt_group, "Generic Alt Group") {
      node node1
      node node2
      node node3
      node node4
      node node5
      node1 -- node2 : label1
      node1 .. node3 : label2
      node1 ~~ node4 : label3
      node1 == node5
    }

• AWS Cloud Group

The AWSCloudGroup along with AWSAccountGroup provides a more AWS-like grouping of resources.

Here is one example using VPCs and private subnets:

    AWSCloudGroup(aws_cloud, "AWS Cloud Group") {
      AWSAccountGroup(aws_acc_group, "AWS Account Group") {
        VPCGroup(vpc_group, "VPC Group") {
          PrivateSubnetGroup(priv_subnet1, "Private Subnet Group") {
            [component] as C1
          }
          PrivateSubnetGroup(priv_subnet2, "Private Subnet Group") {
            [component] as C2
          }
        }
      }
    }

AWS Architecture

On our journey of designing the AWS architecture for our innovative self-destroying email service, we should begin with a high-level overview to lay down the foundation. With PlantUML at our disposal, it's a wise approach to start by sketching the fundamental high-level concepts ⁴ before going to deep into details.

By starting with the organizational units and gradually adding layers of complexity, we can systematically build upon the architecture, ensuring a coherent and comprehensive representation of the entire system. This step-by-step approach allows us to understand each component's role and relationships before moving forward.

In this initial phase, we'll focus on capturing the essence of the architecture, identifying the main components and their relationships. As we move on, we can gradually introduce additional elements/components to achieve a holistic and detailed representation of the mail service.

Remember, a well-structured high-level design serves as a roadmap, guiding us through the design process and identifying potential challenges or areas that require further refinement. With PlantUML as our visual design tool, we can easily iterate and modify the architecture as needed, ensuring that our self-destroying email service is built on a solid and scalable foundation. So, let's start with the big picture and refine it step by step to create an AWS architecture that meets our requirements.

Account level

On the organizational level, we have three accounts: OU-Tech, OU-Security, and OU-DevOps. Each account has a prod environment.

AWSCloudGroup(cloud) {
  GenericGroup(ou_tech, "OU-Tech") {
    AWSAccountGroup(acc_tech_prod, "prod") {
    }
  }

  GenericGroup(ou_security, "OU-Security") {
    AWSAccountGroup(acc_security_prod, "prod") {
    }
  }

  GenericGroup(ou_devops, "OU-DevOps") {
    AWSAccountGroup(acc_devops_prod, "prod") {
    }
  }
}

VPCs and responsibilities

On the VPC level, we have a custom VPC with two private subnets. The VPC has a VPC endpoint to API Gateway. The VPC endpoint is used by the API Gateway to access the EKS cluster.

The DevOps organizational unit also has some responsibilities which are highlighted as "groups" inside the OU.

AWSCloudGroup(cloud) {
  GenericGroup(ou_tech, "OU-Tech") {
    AWSAccountGroup(acc_tech_prod, "prod") {
      VPCGroup(vpc_tech, "Custom VPC") {
        EKSCloud(tech_eks_cluster, "Tech EKS Cluster", "Cluster") {
        }
        VPCEndpoints(tech_vpc_endpoint, "VPC Endpoint", "VPC Endpoint")
      }
    }
  }

  GenericGroup(ou_security, "OU-Security") {
    AWSAccountGroup(acc_security_prod, "prod") {
    }
  }

  GenericGroup(ou_devops, "OU-DevOps") {
    AWSAccountGroup(acc_devops_prod, "prod") {
      GenericAltGroup(devops_cicd_group, "CI/CD") {
      }

      GenericAltGroup(devops_infraprov_group, "Infrastructure provisioning") {
      }

      GenericAltGroup(devops_releasemgmt_group, "Release Management") {
      }
    }
  }
}

Relations

AWSCloudGroup(cloud) {
  GenericGroup(ou_tech, "OU-Tech") {
    AWSAccountGroup(acc_tech_prod, "prod") {
      VPCGroup(vpc_tech, "Custom VPC") {
        EKSCloud(tech_eks_cluster, "Tech EKS Cluster", "Cluster") {
        }
        VPCEndpoints(tech_vpc_endpoint, "VPC Endpoint", "VPC Endpoint")
      }
      APIGateway(tech_api_gw, "API GW", "API GW")
    }

    ' Relationships
    tech_api_gw --> tech_vpc_endpoint
  }

  GenericGroup(ou_security, "OU-Security") {
    AWSAccountGroup(acc_security_prod, "prod") {
      CloudWatch(sec_cloudwatch, "Cloudwatch", "Cloudwatch")
      SimpleStorageService(sec_s3, "S3 Bucket", "S3 Bucket")
      IAMIdentityCenter(sec_iam_center, "IAM", "IAM")

      GenericAltGroup(sec_alerting_group, "Alerting") {
        SimpleNotificationService(sec_sns, "SNS", "SNS")
        LambdaLambdaFunction(sec_lambda, "Lambda", "Lambda")
      }

    }
    ' Relationships
    tech_api_gw --> sec_iam_center
    sec_cloudwatch --> sec_alerting_group
    tech_eks_cluster -- sec_s3
  }

  GenericGroup(ou_devops, "OU-DevOps") {
    AWSAccountGroup(acc_devops_prod, "prod") {
      GenericAltGroup(devops_cicd_group, "CI/CD") {
      }

      GenericAltGroup(devops_infraprov_group, "Infrastructure provisioning") {
      }

      GenericAltGroup(devops_releasemgmt_group, "Release Management") {
      }

      ' Relationships
      devops_infraprov_group -right- acc_tech_prod
      devops_cicd_group -right- tech_eks_cluster
    }
  }
}

What about the rest?

Our diagram is not complete yet. Every group region could have its own diagram (as if you would zoom in into a specific component). Let's have a look how we add Kubernetes related components such as nodes, pods and services ⁵.

AWSCloudGroup(cloud) {
  GenericGroup(ou_tech, "OU-Tech") {
    AWSAccountGroup(acc_tech_prod, "prod") {
      VPCGroup(vpc_tech, "Custom VPC") {
        EKSCloud(tech_eks_cluster, "EKS Cluster", "Cluster") {
          GenericGroup(grou_tech_eks_service, "Kubernetes Service") {
            Containers(tech_eks_pod1, "pod", "Pods")
            Containers(tech_eks_pod2, "pod", "Pods")
          }
        }
        VPCEndpoints(tech_vpc_endpoint, "VPC Endpoint", "VPC Endpoint")
      }
      APIGateway(tech_api_gw, "API GW", "API GW")
    }

    ' Relationships
    tech_api_gw --> tech_vpc_endpoint
  }

  GenericGroup(ou_security, "OU-Security") {
    AWSAccountGroup(acc_security_prod, "prod") {
      CloudWatch(sec_cloudwatch, "Cloudwatch", "Cloudwatch")
      SimpleStorageService(sec_s3, "S3 Bucket", "S3 Bucket")
      IAMIdentityCenter(sec_iam_center, "IAM", "IAM")

      GenericGroup(sec_alerting_group, "Alerting") {
        SimpleNotificationService(sec_sns, "SNS", "SNS")
        LambdaLambdaFunction(sec_lambda, "Lambda", "Lambda")
      }

    }
    ' Relationships
    tech_api_gw --> sec_iam_center
    sec_cloudwatch --> sec_alerting_group
    tech_eks_cluster -- sec_s3
  }

  GenericGroup(ou_devops, "OU-DevOps") {
    AWSAccountGroup(acc_devops_prod, "prod") {
      GenericAltGroup(devops_cicd_group, "CI/CD") {
      }

      GenericAltGroup(devops_infraprov_group, "Infrastructure provisioning") {
      }

      GenericAltGroup(devops_releasemgmt_group, "Release Management") {
      }

      ' Relationships
      devops_infraprov_group -right- acc_tech_prod
      devops_cicd_group -right- tech_eks_cluster
    }
  }
}

Sequence diagrams

When examining the previsouly sketched architecture, it is not immediately clear how the mail service can be used. To gain a better understanding of the fundamental workflows, it is necessary to adopt sequence diagrams. These diagrams should be created for each business use case ⁶.

Without fancy icons

Let's explore some sequence diagrams without icons and additional styling:

• Compose and send mails
  

      @startuml
      title Sending a Self-Destructing Email
  
      actor User
      participant Frontend
      participant AuthenticationService
      participant EmailCompositionService
      participant EncryptionService
      participant LifetimeManagementService
      participant NotificationService
  
      User -> Frontend: Compose email
      Frontend -> AuthenticationService: Authenticate user
      AuthenticationService --> Frontend: User authenticated
      Frontend -> EmailCompositionService: Compose email with content
      EmailCompositionService -> EncryptionService: Encrypt email content
      EncryptionService --> EmailCompositionService: Email content encrypted
      EmailCompositionService -> LifetimeManagementService: Set expiration time
      note right: Expire after N hours
      LifetimeManagementService --> EmailCompositionService: Expiration time set
      EmailCompositionService -> NotificationService: Notify recipient
      NotificationService --> EmailCompositionService: Recipient notified
      EmailCompositionService --> Frontend: Email composition complete
      Frontend --> User: Email sent
      @enduml
  

  
  
  👉 Sending an e-mail
  
  

  
  

  👉 Full PlantUML Code
  
  

• Receive and view mails
  

      @startuml
      actor Recipient
      participant NotificationMicroservice
      participant Frontend
      participant EncryptionMicroservice
      participant LifetimeManagementMicroservice
  
      Recipient -> NotificationMicroservice: Received Email Notification
      NotificationMicroservice -> Frontend: Get Email Data
      Frontend -> EncryptionMicroservice: Decrypt Email Content
      Frontend -> Frontend: Display Email
      Frontend -> LifetimeManagementMicroservice: Check Expiration Status
      LifetimeManagementMicroservice -> Frontend: Email Expired
      @enduml
  

  
  
  👉 Plantuml sequence diagram for receiving and viewing mails
  
  

  
  

  👉 Full PlantUML Code
  
  

• Compose and send mails (with logging)

  Now let's complicate things a little bit and also make sure we log requests and store necessary data to our storage system:
  

      @startuml
      actor User
      participant Frontend
      participant AuthMicroservice
      participant EncryptionMicroservice
      participant CompositionMicroservice
      participant LifetimeManagementMicroservice
      participant LoggingService
      participant DataStorage
  
      User -> Frontend: Compose Email
      Frontend -> AuthMicroservice: Authenticate User
      AuthMicroservice -> Frontend: User Authenticated
      Frontend -> CompositionMicroservice: Send Email Data
      CompositionMicroservice -> EncryptionMicroservice: Encrypt Email Content
      EncryptionMicroservice -> LifetimeManagementMicroservice: Set Expiration Time
      LifetimeManagementMicroservice -> Frontend: Expiration Time Set
      Frontend -> Frontend: Notify User (Email Sent)
      Frontend -> LoggingService: Log Email Sent Event
      Frontend -> DataStorage: Store Email Metadata
      CompositionMicroservice -> DataStorage: Store Encrypted Email Content
      @enduml
  

  
  
  👉 Plantuml sequence diagram for composing and sending mails (with logging)
  
  

  
  

  👉 Full PlantUML Code
  
  

With AWS Icons

Let's add some AWS related icons and some boxes (for emphasizing components that belong together):

• Send mails
  

      @startuml
      ' Epilogue
      skinparam BoxPadding 10
  
      ' !define AWSPuml https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v16.0/dist
      !define AWSPuml /home/victor/work/repos/aws-icons-for-plantuml/dist
      !include AWSPuml/AWSCommon.puml
      !include AWSPuml/Compute/all.puml
      !include AWSPuml/ApplicationIntegration/APIGateway.puml
      !include AWSPuml/General/Internetalt1.puml
      !include AWSPuml/Database/DynamoDB.puml
  
      ' Components
      actor User as User
      APIGatewayParticipant(api_gateway, "API Gateway", "")
  
      box "EKS" #LightBlue
        participant AuthenticationService
        participant EncryptionService
        participant EmailCompositionService
        participant NotificationService
        participant LifetimeManagementService
      end box
  
      ' Relationships
      User -> api_gateway: POST /create-mail
      == Authentication ==
      api_gateway -> AuthenticationService: Authenticate user
      AuthenticationService -> api_gateway: User authenticated
  
      == Mail creation ==
      api_gateway -> EmailCompositionService: POST /create-mail
      EncryptionService --> EmailCompositionService: Email content encrypted
      EmailCompositionService -> LifetimeManagementService: Set expiration time
      note right: Expire after N hours
      LifetimeManagementService --> EmailCompositionService: Expiration time set
  
      == Notification ==
      EmailCompositionService -> NotificationService: Notify recipient
      NotificationService --> EmailCompositionService: Recipient notified
      EmailCompositionService --> api_gateway: Email composition complete
      api_gateway --> User: Email sent
      @enduml
  

  
  
  👉 Sending mail workflow (with icons and boxes)
  
  

  
  

  👉 Full PlantUML Code
  
  

• Send mail (with logging and data storage)

  Now let's add logging and data storage to the sequence diagram
  

      @startuml
      ' Epilogue
      skinparam BoxPadding 10
  
      ' !define AWSPuml https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v16.0/dist
      !define AWSPuml /home/victor/work/repos/aws-icons-for-plantuml/dist
      !include AWSPuml/AWSCommon.puml
      !include AWSPuml/Compute/all.puml
      !include AWSPuml/Storage/all.puml
      !include AWSPuml/ManagementGovernance/CloudWatch.puml
      !include AWSPuml/ApplicationIntegration/APIGateway.puml
      !include AWSPuml/General/Internetalt1.puml
      !include AWSPuml/Database/DynamoDB.puml
  
      ' Components
      actor User as User
      APIGatewayParticipant(api_gateway, "API Gateway", "")
  
      box "EKS" #LightBlue
        participant AuthenticationService
        participant EncryptionService
        participant EmailCompositionService
        participant NotificationService
        participant LifetimeManagementService
      end box
  
      box "Storage" #LightGray
        SimpleStorageServiceParticipant(DataStorage, "S3", "")
      end box
  
      box "Logging" #LightCyan
        CloudWatchParticipant(LoggingService, "CloudWatch", "CloudWatch")
      end box
  
      ' Relationships
      User -> api_gateway: POST /create-mail
      == Authentication ==
      api_gateway -> AuthenticationService: Authenticate user
      AuthenticationService -> api_gateway: User authenticated
  
      == Mail creation ==
      api_gateway -> EmailCompositionService: POST /create-mail
      EncryptionService --> EmailCompositionService: Email content encrypted
      EmailCompositionService -> DataStorage: Save mail metadata and encrypted content
      EmailCompositionService -> LifetimeManagementService: Set expiration time
      note right: Expire after N hours
      LifetimeManagementService --> EmailCompositionService: Expiration time set
  
      == Notification ==
      EmailCompositionService -> NotificationService: Notify recipient
      NotificationService -> LoggingService: Log Email sent event
      NotificationService --> EmailCompositionService: Recipient notified
      EmailCompositionService --> api_gateway: Email composition complete
      api_gateway --> User: Email sent
      @enduml
  

  
  
  👉 Sending mail workflow (with icons and boxes)
  
  
  
  
  

  
  

  👉 Full PlantUML Code
  
  

Outlook

Here are some useful PlantUML related resources:

• plantuml.com
  • Especially sequences, mindmaps, components
  • And for software architecture: class diagrams
• real-world-plantuml.com
• The Hitchhiker's Guide to PlantUML documentation

In the next post, we'll cover the C4 model, a powerful framework for visualizing software and infrastructure architecture using a unified model and language. Stay tuned!

1. I also code for presentations. So the term presentation as code is also a thing. ↩

2. For really cool diagrams you might want to have a look at PlantUML Hitchhikers Guide. ↩

3. In this example I've cloned aws-icons-for-plantuml locally. That's why I've used /home/victor/work/repos/aws-icons-for-plantuml/dist as the location of the AWS icon distribution. But you can still use an external URL such as https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v16.0/dist. ↩

4. You may also check the first post for some diagrams using pen & paper. ↩

5. Also have a look at Hitchhikers Guide on Kubernetes. ↩

6. The examples below don't require the epilogue (styling and additional modules). ↩