HTTP Acceleration with Varnish

Mobile-first 10k Hotel Partners 17 Countries ~9M Downloads

HotelTonight

I WANNA GO FAST

Overview

Reverse Proxies

HTTP Headers

Cache Invalidation

Varnish Configuration Language

Reverse proxy

In computer networks, a reverse proxy is a type of proxy server that retrieves resources on behalf of a client from one or more servers.

Request / Response Cycle

Reverse Proxy

Origin ServerClient

www.hward.com

(CNAME)

hward.herokuapp.com

(or IP Address)

Web application accelerator.

Web application accelerator.

Reverse proxy w/ caching

Cache Miss

Varnish Origin ServerClient

Cache

Cache Hit

Varnish Origin ServerClient

Cache

Initial use of VarnishStarted with a small portion of our traffic.

33% Hits, 1% Misses, 66% Passes

The best traffic is traffic that never hits our servers.

Continue to migrate endpoints to Varnish

Removed 10 EC2 XLarge Instances!

Varnish as a service.

• Dashboards and Stats

• RESTful API

• Killer support team (thanks Peter and Austin)

• Similar pricing to Cloudfront

Fastly Point of Presence (PoP)

Australia PoPs

N. America PoPs

Europe PoPs

Origin Server

N. America

Australia

Europe

Simulated traffic w/ Loader.io

73k req sec 1ms avg. response

HTTP Headers

HTTP header fields are components of the message header of requests and responses in the Hypertext Transfer Protocol.

Rails Default Behavior

Varnish Origin ServerClient

Cache

$ curl -v https://launchpad.37signals.com/basecamp -o /dev/null < HTTP/1.1 200 OK < Cache-Control: max-age=0, private, must-revalidate < Set-Cookie: _launchpad_session=[DIGEST]; path=/; HttpOnly; secure

Opt-in to Edge Cache

Edge-Cache Headers

Cache-Control Header:

public, max-age or s-maxage > 0, and remove any cookies from the response.

$ curl -v http://www.example.com -o /dev/null < HTTP/1.1 200 OK < Cache-Control: max-age=30, public

Only cache publicly accessible pages.

max-age vs.

s-maxage

max-age

s-maxageused only by proxy for content expiration

used on both client and proxy for content expiration

Cache-Control Headers for Static Assets

$ curl -v http://www.hward.com/assets/blog-f764a70dc0ca4e7bf340d1.css < HTTP/1.1 200 OK < Cache-Control: public, max-age=31557600 < Content-Type: text/css < Status: 200 OK < Via: 1.1 varnish

Cache-Control Headers for Dynamic Content

$ curl -v http://www.hward.com < HTTP/1.1 200 OK < Cache-Control: public, no-cache, s-maxage=31557600 < Content-Type: text/css < Status: 200 OK < Via: 1.1 varnish

Rails Controllers

Verify cache is warming up

$ curl -v http://www.hward.com -o /dev/null < HTTP/1.1 200 OK < X-Served-By: cache-sv61-SJC3 < X-Cache: MISS < X-Cache-Hits: 0 !$ curl -v http://www.hward.com -o /dev/null < HTTP/1.1 200 OK < X-Served-By: cache-sv61-SJC3 < X-Cache: HIT < X-Cache-Hits: 1

Cache Invalidation

• Time based expiration

• Resource based expiration

• Surrogate-Keys

Cache TTL Hit Ratio Origin Requests / Minute

5 sec 98.00% 20

30 sec 99.80% 2

1 min 99.90% 1

5 min 99.997% <1

1000 Requests / Minute

Cache TTL Hit Ratio Origin Requests / Minute

5 sec 99.96% 20

30 sec 99.996% 2

1 min 99.998% 1

5 min 99.999% <1

1000 Requests / Minute50,000

PURGE Requests

Invalidate cache with PURGE request to URL.

$ curl -v -X PURGE http://www.hward.com > PURGE / HTTP/1.1 < HTTP/1.1 200 OK < Status: 200 OK < Via: 1.1 varnish {"status": "ok", "id": "68-1392243590-232248"}

Note: In Production make sure to whitelist IP’s that can Purge.

Surrogate-Keys (Fastly Specific)

posts/1

comments/1

comments/2

http://www.fastly.com/blog/surrogate-keys-part-1

Many-to-Many Relationship Between Keys and Pages

posts/1

Purging a Surrogate-Key

posts/1

Varnish Configuration Language (VCL)

Imagery Service

640x260640x900

412x 412

Dynamically resized images for all devices.

Initially used Magickly Gem

example.com/image.jpg?resize=500x500#

Varnish S3 BucketClientMagickly

Gem

Transition to ImgIX

example.com/image.jpg?w=500&h=500&crop=fit

Varnish S3 BucketClient

Re-write URL for backwards compatibility with VCL

Additional Topics

• Vary Headers

• Logging

• Shielding

• Grace-period for stale cache

Harlow Ward @futuresanta harlow@hoteltonight.com

$25 Promo Code: HARLOW

Questions?