AWS Webcast - High Availability with Route 53 DNS Failover

transcript

High Availability with Route 53 DNS Failover

Sean Meckley, Product Manager, Amazon Route 53

Paul Kearney, Chief Software Architect, InfoSpace

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

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

How it Works

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

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

• 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?

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

• 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?

Architectures Enabled by DNS Failover

Two Basic Use Cases for DNS Failover

• Active / Active

• Latency Based Routing (LBR)

or Weighted Round Robin

• 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

Primary

(Active) Amazon Route 53

Data Volume

Database

Server

EC2 Web

App Server

AWS Region

Health Check

= Healthy

Secondary

(inactive)

Simple Failover Use Case

Primary

(Inactive) Amazon Route 53

Data Volume

Database

Server

EC2 Web

App Server

AWS Region

Health Check

= Unhealthy

Secondary

(Active)

Simple Failover Use Case

LBR (Active) Amazon

Route 53

AWS Region 1

Elastic Load

Balancer

Volume

Database

Server

Web App

Server

AWS Region

Health Check

= Healthy

AWS Region 2

Elastic Load

Balancer

Volume

Database

Server

Web App

Server

AWS Region

Health Check

= Healthy

LBR (Active)

Multi-Region Failover

LBR (Active) Amazon

Route 53

AWS Region 1

Elastic Load

Balancer

Volume

Database

Server

Web App

Server

AWS Region

Health Check

= Healthy

AWS Region 2

Elastic Load

Balancer

Volume

Database

Server

Web App

Server

AWS Region

Health Check

= Unhealthy

Route 53 Stops Routing to

This Region

LBR (Inactive)

Multi-Region Failover

Types of Endpoints and How to Get Failover for

Configuring DNS Failover for Elastic Load

Balancing Endpoints

DNS Failover for ELB

Go to Hosted Zones >> Record Sets

• For records pointing to an EC2 instance:

• Create a Health Check in the Route 53 console or using the

• Associate one or more Route 53 resource record set (RRset)

with the health check

EC2 Instances as Endpoints

• 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

• Associate one or more Route 53 resource record set (RRset)

with the health check

Non-AWS Resources as Endpoints

Configuring DNS Failover for All Other

Endpoints (EC2 and Arbitrary IPs)

DNS Failover for EC2 and Other Endpoints

Step 1: Create a Health Check

Step 2: Associate the Health Check with a

Resource Record Set

Go to Hosted Zones >> Record Sets

How Do I See Health Status?

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

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.

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

Customer Example: Multi-Region Failover

Scenario

AWS & InfoSpace Route 53 DNS Failover

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

InfoSpace Search

Search API Search Sites

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

• Broad geographical

distribution

Search Site Users

Global Distribution of Traffic

AZ AZ AZ

Setup LBR – xml request

Setup LBR – dnscurl

Test 1 – Simple script

Test 2 – Fire and Forget

Production System under test

Test 2 – Fire and Forget

Results

• Regional failover in 150 seconds consistently

• Decreased latency – 25% less latent worldwide

• Replaced expensive network gear from datacenter

Thank You!

AWS Webcast - High Availability with Route 53 DNS Failover

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