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DNS

  • Domain Name System which translates the human friendly hostnames into the machine IP addresses.
  • www.google.com =>172.217.18.36
  • Any zone costs 50 cents/month
  • Public vs Private hosted zones

Records TTL

  • TTL - Time to live
  • High TTL - e.g. 24 hr
    • less traffic on Route 53
    • Possibly outdated records
  • Low TTL - e.g. 60s
    • More traffic on Route 53 ($$)
    • Records are outdated for less time
    • Easy to change records
  • Except for Alias records, TTL is mandatory for each DNS record

CNAME vs Alias

  • AWS resources (Load Balancer, CLoudFront..) expose an AWS hostname:
    • lb l-1234.us-east-2.elb.amazonaws.com and you want myapp.mydomain.com
  • CNAME:
    • Points a hostname to any other hostname (app.domain.com => blabla.anything.com)
    • You cannot create a CNAME for the Apex record (root domain)
  • Alias:
    • Points a hostname to an AWS Resource (app.mydomain.com => blabla.amazonaws.com)
    • WORKS for ROOT DOMAIN and NON ROOT DOMAIN (aka, mydomain.com)
    • Free of charge
    • Native health check
    • Only supported for A and AAAA record types
    • Cannot set alias for an EC2 instance name

Routing Policies

  • Simple

    • Typically, the simple type of routing policy will resolve to a single resource
    • If the record resolves to multiple values, the client will choose a random one
    • When using the Alias record type, the record can only resolve to one resource

  • Weighted

    • Control the % of the requests that go to each specific resource.
    • Assign each record a relative weight
      • $ \text traffic {(%)} = {\displaystyle \text {weight for a specific record } \over \displaystyle \text {sum of all the weights for all records }} $
      • The sum of the weights of all records does not need to equal 100
    • DNS records must have the same name and type
    • Can be associated with Health Checks
    • Use cases: load balancing between regions, testing new application versions

  • Latency

    • Redirect to the resource that has the least latency close to us
    • Super helpful when latency for users is a priority
    • Latency is based on traffic between users and AWS Regions
    • Germany users may be directed to the US (if that’s the lowest latency)
    • Can be associated with Health Checks (has a failover capability)

  • Failover

  • Geolocation

    • Different from latency based
    • This routing is based on user location
    • Should create a “Default” record (in case there’s no match on location)
    • Use cases: website localization, restrict content distribution, load balancing
    • Can be associated with Health Checks

  • Geoproximity

    • Route traffic to your resources based on the location of users and resources
    • Ability to shift more traffic to resources based on the defined bias
    • To change the size of the geographic region, specify bias values:
      • To expand (1 to 99)- more traffic to the resource
      • To shrink (-1 to 99)- less traffic to the resource
    • Resources can be:
      • AWS resources (specify AWS region)
      • Non-AWS resources (specify Latitude and Longitude)
    • You must use Route 53 Traffic Flow to use this feature

  • Health Checks

    • HTTP Health Checks are only for public resources. You must create a CloudWatch Metric and associate a CloudWatch Alarm, then create a Health Check that checks the alarm
    • 15 global health checkers
    • Health checks methods:
      • Monitor an endpoint
        • Healthy/unhealthy threshold - 3 (default)
        • Interval 30 seconds
        • Supports HTTP, HTTPS, and TCP
        • if > 18% of health checkers report the endpoint is healthy, Route53 considers it healthy.
        • You can choose which locations you want Route53 to use
        • You must configure the firewall to allow traffic from the health checkers
      • Calculated Health Checks
        • Combine the results of multiple health checks into a single health check

Configuring Amazon Route 53 to route traffic to an S3 Bucket

  • An S3 bucket that is configured to host a static website
    • You can route traffic for a domain and its subdomains, such as example.com and www.example.com to a single bucket.
    • Choose the bucket that has the same name that you specified for Record name
    • The name of the bucket is the same as the name of the record that you are creating
    • The bucket is configured as a website endpoint