This webinar will be discussing how to use DNS Failover to a range of high-availability architectures, from a simple backup website to advanced multi-region architectures.

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High Availability with Route 53 DNS Failover
Sean Meckley, Product Manager, Amazon Route 53
Paul Kearney, Chief Software Architect, InfoSpace

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Agenda
About Route 53
What is DNS Failover?
Architectures enabled
Types of endpoints and how to get failover for each
How do I see health status?
Customer example: multi-region failover scenario
Q&A

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What is Route 53?

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What is Route 53?
AWS’s authoritative Domain Name
(DNS) service
Highly available and scalable
Offers tools that provide flexible,
high-performance, and highly
available architectures on AWS

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How it Works
5
Users DNS Resolver Route 53
Where is
www.example.com?
I don’t know – I’ll
ask the authority
192.0.2.1 192.0.2.1
53

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What is DNS Failover?

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What is DNS Failover?
Failover
Only return answers for resources
that are healthy and reachable
from the outside world, so that
your end users are routed away
from a failed or unhealthy part of
your application
Health checks
Automated requests sent over
the Internet to your application
to verify that your application is
reachable, available, and
functional
+

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• Improve availability of your applications running on AWS
• So that you can configure backup and failover scenarios for
your own applications
• Enable highly available multi-region architectures on AWS
• Providing a means to fail over across AWS regions
Why DNS Failover?

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Endpoint: an Internet location, defined as an IP address, URL, or ELB name,
that is checked periodically to determine whether a healthy response is
returned.
• This represents an ELB, and EC2 instance, or an arbitrary IP address
Health Check: This is what your create in the Route 53 console or API.
• Has a status of either healthy or unhealthy, depending on the results of
our probing the endpoint
• You can associate one or more DNS records with the health check
DNS Failover: A Glossary

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• Route 53 conducts health checks from within each AWS region
• To perform a health check, Route 53 makes a request to the your specified IP
address / URL. If we get a successful response, the health check passes. If
not, the health check fails.
• If a health check fails, all DNS records that are dependent on the health check
will be made inactive; DNS records that have been configured as backups will
become active
• Total time from endpoint failure to DNS failover is about 3 minutes
How Does it Work?

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Architectures Enabled by DNS Failover

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Two Basic Use Cases for DNS Failover
• Active / Active
• Latency Based Routing (LBR)
or Weighted Round Robin
(WRR)
• Stop routing to a region if it is
unavailable, for example:
• Large-scale networking issue
or AWS region outage
• Your application is down in a
particular region
• Simple Failover (Active / Standby)
• Primary site + backup site
• Lets you run both a primary and
backup site and automatically
failover to the backup site in the
event that the primary site goes
down

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Primary
(Active)
Amazon
Route 53
Data
Volume
Database
Server
EC2 Web
App Server
AWS Region
Health Check
= Healthy
Secondary
(inactive)
Simple Failover Use Case

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Primary
(Inactive)
Amazon
Route 53
Data
Volume
Database
Server
EC2 Web
App Server
AWS Region
Health Check
= Unhealthy
Secondary
(Active)
Simple Failover Use Case

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LBR (Active) Amazon
Route 53
AWS Region 1
Elastic Load
Balancer
Data
Volume
Database
Server
Web App
Server
AWS Region
Health Check
= Healthy
AWS Region 2
Elastic Load
Balancer
Data
Volume
Database
Server
Web App
Server
AWS Region
Health Check
= Healthy
LBR (Active)
Multi-Region Failover

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LBR (Active) Amazon
Route 53
AWS Region 1
Elastic Load
Balancer
Data
Volume
Database
Server
Web App
Server
AWS Region
Health Check
= Healthy
AWS Region 2
Elastic Load
Balancer
Data
Volume
Database
Server
Web App
Server
AWS Region
Health Check
= Unhealthy
Route 53 Stops Routing to
This Region
LBR (Inactive)
Multi-Region Failover

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Types of Endpoints and How to Get Failover for
Each

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Configuring DNS Failover for Elastic Load
Balancing Endpoints
DNS Failover for ELB

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Go to Hosted Zones >> Record Sets
DNS Failover for ELB

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DNS Failover for ELB

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• For records pointing to an EC2 instance:
• Create a Health Check in the Route 53 console or using the
API
• Associate one or more Route 53 resource record set (RRset)
with the health check
EC2 Instances as Endpoints

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• For records pointing to a non-AWS resource:
• The endpoint must have a fixed IP address
• Create a Health Check in the Route 53 console or using the
API
• Associate one or more Route 53 resource record set (RRset)
with the health check
Non-AWS Resources as Endpoints

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Configuring DNS Failover for All Other
Endpoints (EC2 and Arbitrary IPs)
DNS Failover for EC2 and Other Endpoints

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Step 1: Create a Health Check
DNS Failover for EC2 and Other Endpoints

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DNS Failover for EC2 and Other Endpoints

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DNS Failover for EC2 and Other Endpoints

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DNS Failover for EC2 and Other Endpoints

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DNS Failover for EC2 and Other Endpoints

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Step 2: Associate the Health Check with a
Resource Record Set
DNS Failover for EC2 and Other Endpoints

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Go to Hosted Zones >> Record Sets
DNS Failover for EC2 and Other Endpoints

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DNS Failover for EC2 and Other Endpoints

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How Do I See Health Status?

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Like all metrics stored in CloudWatch, you can view them from the AWS
Management Console, set alarms, and fire notifications.
Navigate to the Route 53 console and click “Health Checks” in the left hand
nav to view your health checks. Click “View Graph”.
Monitoring Health Check Status

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This takes you to the CloudWatch console. Note that for newly created health
checks, it takes about five minutes for metrics to start appearing in
CloudWatch.
Monitoring Health Check Status

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From here, you can
create an alarm just
like for any other
CloudWatch metric,
and you can use the
alarm to trigger SNS
notifications (for
example, to send an
email to yourself) if
your endpoint goes
down.
Monitoring Health Check Status

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Customer Example: Multi-Region Failover
Scenario

37. AWS & InfoSpace
Route 53 DNS Failover

38. InfoSpace Overview
Since 1996, our mission has been to make it fast and easy for users to
find what they need online.
Paul Kearney, Chief Software Architect
http://tech.infospace.com

39. InfoSpace Search
Search APISearch Sites

40. Types of Users
• 6.5 billion clicks/month
• Broad geographical
distribution
• 150+ partners worldwide
• Located primarily in US, EU
• 2 billion queries/month
Search API Partners Click Users
• 400 million queries per
month
• Broad geographical
distribution
Search Site Users

41. Global Distribution of Traffic
AZ
AZ
AZ AZ
AZ
AZAZ
AZ
AZ

42. Setup LBR – xml request

43. Setup LBR – dnscurl

44. Test 1 – Simple script

45. Test 2 – Fire and Forget
Production System under test
Async

46. Test 2 – Fire and Forget
LBR
LBR

47. Results
• Regional failover in 150 seconds consistently
• Decreased latency – 25% less latent worldwide
• Replaced expensive network gear from datacenter

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Q & A

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Thank You!