AWS Route53 (Routing)

Simple Routing Policy (SRP)

• Single resource
• No healthcheck

Weighted Routing Policy (WRR)

• Create multiple Resource Record Sets (group)
  • Identical name, type
  • Set identifier and weight
• optionally healthcheck
• 40% to Server A
• 60% to Server B
• Supported Record Types
  • A, AAAA, CNAME, TXT
• Use case
  
  • A/B testing

Latency Routing Policy (LRP)

• AWS performs ongoing latency checks
• Resource Records Sets: EC2 instance (IP address), ELB
• Optionally: healthcheck
• Create Latency Record Set in each region
  • e.g. "us-west-1" and "eu-west-1"
• Supported Record Types
  • A,AAAA,CNAME,TXT
• Use case
  • Increase performance

Geolocation Routing Policy

• Based on location of the browser
• Optionally: healthcheck
• Use cases
  • Localized version
  • Restrict to countries with distribution rights
  • Compliance
• Scope
  • Continent
  • Country
  • State (US)
• Non-identified location
  • Default
  • No answer
• Uses EDNS to improve accuracy
• Bias
  • Allows to configure the "area" covered by particular service 
  • Traffic Flow only

Failover Routing Policy

• Active-Passive
• Use case
  
  • High Availability
  • Must tolerate downtime during switchover

Multivalue Answer Routing Policy

• Returns multiple values
• Records can be healthchecked individually

Healthcheck

• What to monitor
  • Endpoint - works like Pingdom
  • Status of other healthchecks (i.e. calculated healthcheck)
  • CloudWatch Alarm (for non-public resources)
• Notifications
  • CloudWatch Alarm
  • SNS
• Associated with Resource Record Set
• Evaluate Target Healthcheck (ALIAS records only)
  • ALIAS, weighted ALIAS, latency ALIAS, geolocation ALIAS, failover ALIAS
  • Allows routing to back-out from the branch
• Protocols: HTTP, HTTPS, TCP
  • Does not follow HTTP redirects
  • No SSL validation
  • SNI supported
• Interval: 30s (fast interval = 10s)
• Type
  • HTTP
  • HTTPS
  • HTTP_STR_MATCH 
  • HTTPS_STR_MATCH
  • TCP
• Published to CW

DNS routing decision tree example

• Latency alias resource record set (example.com)
  • 1 in eu-west 
  • 1 in us-east
  • DNS query for example.com resolves to eu-west (AWS latency based)
• Weighted resource record set
  • In each region there are 2 instances
  • Each record set associated with healthcheck
• Evaluate Target Healthcheck
  • Allows to back-off from the initial latency decision if eu-west is unhealthy

Traffic Flow

• Simplifies creating complex rules
• Visual editor available
  • Create set of rules to decide how requests are routed to the application
  • They will be translated to a tree of records
• Policy Record
  • Associate policy with DNS name
  • Billed for each record