AWS re:Invent 2016: Amazon CloudFront Flash Talks: Best Practices on Configuring, Securing and Monitoring your Distribution (CTD301)

© 2016, Amazon Web Services, Inc. or its Affiliates. All rights reserved.

Best Practices for Configuring, Securing, and

Monitoring Your Amazon CloudFront Distribution

Alec Peterson

General Manager, Amazon CloudFront

Anton Radlein

Software Development Manager, Amazon CloudFront

Cherie Wong

Sr. Software Development Manager, Amazon CloudFront

Efrain Fuentes

Enterprise Solutions Architect

CTD301

What to Expect from the Session

• How Amazon CloudFront delivers content

• Configuring your cache on CloudFront

• Measure application performance with real user

monitoring (RUM)

• Stop malicious viewers with CloudFront and AWS WAF

How CloudFront delivers

content

Definitions

• Viewer

• An end-user requesting content from CloudFront

• On a mobile device, desktop or other internet-connected

device

• CloudFront POP

• Point Of Presence, also referred to as an Edge Location

• Located in datacenters in major metropolitan areas, directly

connected to multiple ISPs

• Several racks of servers and network equipment, terminating

viewer connections

CloudFront delivering content

• Multiple identical (more or less) locations

• Location selection is critical

• Viewer perspective

• Latency

• Throughput

• CloudFront perspective

• Availability

• Capacity

• Location

What does ‘routing’ actually mean?

• Packet routing

• Purely destination-

based

• Limited ability to route

around congestion

What does ‘routing’ actually mean?

• Request routing

• Latency

• Throughput

• Capacity

• Geography

• Done at the DNS layer (or higher)

How does CloudFront perform routing?

CloudFront

edge

location

1.1.1.1

ISP NS

cloudfront.net

authoritative NS

viewer

(recursive lookup) distribution-id.cloudfront.net

(IP address of optimal CloudFront Edge location) 1.1.1.1

Primarily at the DNS layer• Recursive resolver IP routing

What’s wrong with this picture?

What happened?

• A divergent resolver

• Resolvers that serve a wide set of users across many

networks/geographies

• VPN users

• Distributed corporate networks

• What can be done?

• Use a local resolver

• Use a resolver that supports EDNS0 ECS

What is EDNS0 client-subnet (ECS)?

• IETF open internet-draft

• Informational RFC 7871

• DNS query includes information about the network that

originated the query:

• First three octets of a IPv4 address commonly used

(1.2.3.0/24)

• No client-side resolver modifications necessary

• Some common open resolvers (such as Google’s 8.8.8.8

anycast resolver) support it

EDNS0 ECS-enabled DNS resolution

Key takeaways

• Where you are routed depends on many factors

• Network

• Geographic Location

• Individual POP status

• DNS is an imperfect request routing mechanism

• But it is also ubiquitous

• If your customers use ECS-enabled resolvers, their

experience will improve

Configuring your cache on

CloudFront

Why cache?

Two Laws:

1. Better performance for your viewers.

2. Less load on your origin.

What to expect

• What we do with a viewer request?

• How do we cache?

• Generating cache keys

• Managing your cache

• Setting Cache-Control headers

• Configuring your distribution and cache behaviors

• Additional Best Practices

• Versioning your assets

• Forwarding only required values

• Monitor your logs

Origin

IAD Edge Cache

IAD12 ATL50 JFK1 JAX1

NRT Edge Cache

NRT12 NRT53 NRT52 NRT20

Caching tiers

What happens with each request?

Is it in

cache?

Is it

expired?

Revalidate

with Origin

Origin

responds

with 304 (Not

Modified)

Origin

responds

with 200

(OK) and

latest version

of object

Forward

request to

origin

Y Y

NN

Viewer

Request

Hit / Refresh Hit

Miss

Cache

it

How do we generate a cache key?

Use the host header to create an internal canonical URL.

E.g., d123.cloudfront.net, example.com

Then…

- Remove query strings

- Remove the protocol

- Add accept-encoding (i.e., gzip, identity)

Managing your cache from your origin

Expires headers from origin

Expires reflects when the cache must go back to the origin

server to see if the object has changed.

It is a fixed point in time and accuracy relies on clock

synchronization.

< Expires: Fri, 1 Dec 2017 12:34:50 GMT

Cache-Control headers from origin

These directives give you fine-grained control over what is cached and

for how long (in seconds):

< Cache-Control: max-age=300< Cache-Control: max-age=30, s-maxage=3600

Example: max-age=0, s-maxage=86400 for display ads

Browser

Shared Edge Cache

Cache-Control headers (examples)

Static Assets Login Landing

Pages

Live Streaming

Manifests

Media Fragments

*.css, *.js, images,

software

downloads

index.html /*.m3u8 /*.ts

Cache-Control:

public; max-age=31536000

Cache-Control: no-cache=Set-

Cookie; max-age=30

Cache-Control:

public; max-age=2

Cache-Control:

public; max-age=31536000

Dynamic content? Cache it.

Use Cache-Control directives to minimize load on your origin:

- no-cache: cache & ask origin

- max-age=0: cache & ask origin

Other options:

- no-store: never cached at the edge nor by the browser

- private: never cached at the edge, but might be cached

by the browser

Managing your cache from CloudFront

Cache behaviors

on CloudFront

Specify caching configurations

based on URL path matching

(i.e., for different content).

Whatever you forward affects

your cache key. Use Trusted

Advisor checks!

Be wary of:

• Forwarded headers

• Query string forwarding

• Cookie forwarding

Set Min, Max, and Default TTLs for CloudFront

Min TTL Max TTLmax-age /

Expires

Browser Edge Cache

max-age /

s-maxage /

Expires

Max TTLmax-age /

Expiresmax-age /

s-maxage /

Expires

Min TTL

Max TTLmax-age /

s-maxage /

Expires

Min TTLmax-age /

Expires

A couple tips…

Errors? Cache them too!

Cache and return a custom error

page and response code for each

HTTP error code.

Give your origin just the right

amount of time to recover.

Enable faster iteration of new styles without issuing invalidations.

Protect against browsers that don’t honor your Cache-Control headers.

<linkhref="//assets.example.com/assets/v1/css/jumbotron-narrow.css“rel="stylesheet">

<linkhref="//assets.example.com/assets/v2/css/jumbotron-narrow.css“rel="stylesheet">

<linkhref="//assets.example.com/assets/css/jumbotron-

narrow.css?<md5sum>“rel="stylesheet">

Version your assets

Minimize forwarded values

All forwarded headers are

used as part of the cache

key, which means it

dramatically reduces your

cacheability.

When in doubt, check the logs!

#Version: 1.0 #Fields: date time x-edge-location sc-bytes c-ip cs-method cs(Host) cs-uri-stem sc-status cs(Referer) cs(User-Agent) cs-uri-query cs(Cookie) x-edge-result-type x-edge-request-id x-host-header cs-protocol cs-bytes time-taken x-forwarded-for ssl-protocol ssl-cipher x-edge-response-result-type cs-protocol-version 2014-05-23 01:13:11 FRA2 182 192.0.2.10 GET d111111abcdef8.cloudfront.net /view/my/file.html 200 www.displaymyfiles.com Mozilla/4.0%20(compatible;%20MSIE%205.0b1;%20Mac_PowerPC) - zip=98101 RefreshHit MRVMF7KydIvxMWfJIglgwHQwZsbG2IhRJ07sn9AkKUFSHS9EXAMPLE== d111111abcdef8.cloudfront.net http - 0.001 - - - RefreshHit HTTP/1.1 2014-05-23 01:13:12 LAX1 2390282 192.0.2.202 GET d111111abcdef8.cloudfront.net /soundtrack/happy.mp3 304 www.unknownsingers.com Mozilla/4.0%20(compatible;%20MSIE%207.0;%20Windows%20NT%205.1) a=b&c=d zip=50158 Hit xGN7KWpVEmB9Dp7ctcVFQC4E-nrcOcEKS3QyAez--06dV7TEXAMPLE== d111111abcdef8.cloudfront.net http - 0.002 - - - Hit HTTP/1.1

Log CloudFront request IDs

Nginx:

log_format main '$remote_addr - $remote_user [$time_local] "$request" ‘ '$status $body_bytes_sent "$http_referer" ‘ '"$http_user_agent" http_x_forwarded_for" "$http_x_amz_cf_id"';

Apache:

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" \"%{X-Amz-Cf-Id}i\"" combined

Key takeaways

• Set Cache-Control headers appropriately for your

content

• Cache dynamic content

• Create multiple cache behaviors and adapt

configurations for your content type, including errors

• Forward only required values

• Version your assets

• Log your request IDs!

Measure application

performance with RUM

Measure application performance with RUM

Synthetic monitoring vs. real user monitoring (RUM):

• Synthetic monitoring overview

• RUM overview

• When to use one over the other (baselining vs. gaining

situational insight)

What is synthetic monitoring?

Pros:

• Consistent signal of service health

• Easy to setup (kind of)

• Baseline performance

synthetic monitoring

configuration

synthetic

monitoring

portal

web application

simulated users

What is synthetic monitoring?

Pros:

• Consistent signal of service health

• Easy to setup (kind of)

• Baseline performance


configuration

web application

simulated users

Where synthetic measurements go wrong

Cons:

• Network path to your application might not be representative

• Special cases and snowflakes


configuration

web application

simulated usersreal

user

Where synthetic measurements go wrong

Cons:

• Network path to your application might not be representative

• Special cases and snowflakes


configuration

web application

simulated usersreal

user

How do you feel about RUM?

web application

real users

script injected in

web page HTTP

response

RUM

provider

portal

• Script injected in web page

• Script beacons data back from the user’s browser session to the

RUM provider

• RUM provider portal aggregates the data for analysis

What can RUM tell you?

• What should my next optimization be?

• What is the cause of a loss of availability?

*Reference: https://developers.google.com

Network optimizations: connections

Connection definitions:

• Queueing – Time spent waiting to begin processing

• Stalled/Blocking – Total time spent in queue or proxying

• DNS lookup – Time taken to receive DNS records (like A or

AAAA)

• Initial connection – Inclusive of TCP handshake and negotiating

SSL

Network optimizations: requests

Request definitions:

• Request sent – HTTP request sent time

• TTFB - Time To first byte

• Content download – Time to last byte

Network optimizations: head of line blocking

Serialized requests could be your bottleneck due to head of line blocking in

HTTP 1.1 if you’re serving from the same origin!

Network optimizations: Key takeaways

Insights from this example:

• Evaluate your user-base

• Know your data

• Look at the right data

Optimizations:

• Use CloudFront!

• Origin as close to your end-users as possible (multi-region)

• HTTP/2

Best practices for configuring RUM on CloudFront

• Availability: Test your critical resources

• Index pages

• Video manifests

• Critical resources required for page load

• Performance: Capture Total Load time

• First-Byte latency is not always important. Know your content

and optimize on the appropriate dimension!

Stop malicious viewers with

CloudFront and AWS WAF

Securing your CloudFront distribution

• Leverage AWS WAF with preconfigured protections

• Configure CloudFront to serve private content

• Automate security response by using services like AWS

Lambda

• Leverage AWS Certificate Manager for SSL

AWS WAF

AWS WAF preconfigured protections


Access Handler


Log Parser


IP List Parser


http://docs.aws.amazon.com/solutions/latest/aws-waf-security-automations/

Private content – restrict origin access

Amazon S3

Origin Access Identify (OAI)• Prevents direct access to your Amazon

S3 bucket

• Ensures performance benefits to all

customers

Custom origin

Block by IP address• Whitelist only the Amazon CloudFront

IP range

• Protects origin from overload

• Ensures performance benefits to all

customers

Signed URLs

• Add signature to the Querystring in

URL

• Your URL changes

• Use to restrict access to individual

files

Signed Cookies

• Add signature to a cookie

• Your URL does not change

• Use to restrict access to multiple

files

Private content – signed URLs and cookies

Automate security response

• Subscribe to Amazon SNS notifications for changes to

IP ranges

• Automatically update security groups

AWS Lambda

Amazon CloudFront

Amazon SNS

Security group

Web app

server

Web app

serverAWS IP ranges

Update IP rangeSNS message

https://github.com/awslabs/aws-cloudfront-samples

Leverage AWS Certificate Manager for SSL

Key takeaways

• Leverage AWS WAF

• Secure your origin and content

• Automate security response

Thank you!

Remember to complete

your evaluations!

Technology

AWS re:Invent 2016: Amazon CloudFront Flash Talks: Best Practices on Configuring, Securing and Monitoring your Distribution (CTD301)