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Custom Domains Support

Production applications typically require custom domains, so that they can be reached at my-app.my-agency.gov rather than my-app.app.cloud.gov. We’ve used several different approaches for this problem, and considered even more approaches. For historical context, this document outlines a range of approaches, along with pros and cons.

  • Manually create load balancers per domain (used before CDN domain broker)
    • Design
      • Customers file a support ticket
      • Operators create a load balancer for the domain
      • Operators upload certificates
    • Advantages
      • No custom code
    • Disadvantages
      • No automation
      • No self-service
  • CDN domain broker (currently in use)
    • Design
      • Terminate TLS on CloudFront, managed by service broker
      • Forward to cloud.gov origin over public network
    • Advantages
      • Caching, edge serving, lambda support
    • Disadvantages
      • Not FedRAMP approved as of early 2018
      • Users may not need or want caching; must expose and explain caching options
      • No websocket support
      • Specific to AWS
  • ALB domain broker (in development)
    • Design
      • Terminate TLS on ALB, managed by service broker
      • Forward to cloud.gov routers over private network
      • Pre-provision load balancers so that BOSH can manage associations between load balancers and routers
      • Associate multiple domains with each load balancer using SNI
    • Advantages
      • Supports websockets
      • Simple to configure and explain for users
    • Disadvantages
      • Not a CDN
      • Specific to AWS
  • Custom TLS termination proxy broker
    • Design
      • Terminate TLS on haproxy/nginx/traefik
      • Colocate with cloud.gov routers, or forward over private network
      • Store proxy state (endpoints, certificates, etc) in etcd/consul; use conf or consul-template to manage configuration files
    • Advantages
      • Can run on any IAAS
    • Disadvantages
      • Increased operational overhead of running additional services (proxy servers, key-value store)
      • Not a CDN
  • TLS termination proxy without broker
    • Design
      • Watch for customer domains via CF API
      • Automatically provision certificates for customer domains with CNAME/ALIAS records
    • Advantages
      • No broker required; just cf create-domain and configure DNS
    • Disadvantages
      • No obvious interaction points for DNS challenge; could email DNS challenge token to customers
      • No customer feedback about provisioning stattus
  • Do nothing
    • Design
      • Document options for custom domains that live outside the cloud.gov boundary, like Cloudflare or Akamai
    • Advantages
      • No burden on operators
    • Disadvantages
      • Customers may not be able to procure external services
      • Customers may not have knowledge to manage external services

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