Apache Traffic ServerHTTP Proxy Server on the Edge

Leif HedstromEngineer

leif@yahoo-inc.comzwoop@apache.org

Agenda

History and background of Traffic Server

Brief introduction to HTTP intermediaries

Concurrency problems (and solutions)

Choosing an intermediary

Building a CDN

TCP connection management

Server Load Balancer (if time permits)

Origins of the software

Open Source benefits

Forward Proxy

Reverse Proxy

Intercepting Proxy

The concurrency problem

Solution 1: Multithreading

Problems with multi-threading

Solution 2: Event Processing

Problems with event processors

Traffic Server threads model

Plenty of FOSS Proxy Servers

Choosing an intermediary

SMP Scalability and performance

Traffic Server performance

350,000 requests / sec in production CDN- 30 Gbps / second

Max capacity is at least 10x normal usage, to deal with massive spikes.

85,000 requests / sec with small content out of cache, for a single (lab)box

3.6Gbps out of a single box, with larger content (4x GigE NIC bonded)

(all numbers from Y! CDN and lab testing).

HTTP/1.1 Features

Ease of use, extensible

Traffic Server making Ops easy

Traffic Server will restart automatically if it crashes

Traffic Server will kill itself if it isn’t responding

Traffic Server can reload most configurations without server restarts

Adding plugins is a matter of dropping in the shared object, and restarting

Stats and configurations are accessible via command line utilities

Example evaluation sheet

ATS HAproxy nginx Squid Varnish mod_proxy

Worker Threads Y N N N Y Y

Multi-Process N Y Y N Y Y

Event-driven Y Y Y Y N N?

Plugin APIs Y N Y part Y Y

Forward Proxy Y N N Y N Y

Reverse Proxy Y Y Y Y Y Y

Transp. Proxy N Y Y Y N N

Load Balancer part Y! Y Y Y Y

Cache Y N Y Y Y Y

ESI soon N N Y Y N

ICP Y N N Y N N

Keep-Alive Y N Y Y Y Y

SSL Y N Y Y N Y

Pipeline Y N Y Y N Y

Operations is important!

Yahoo! Traffic Server Use Cases

Content Delivery Network

CDN on the Edge

Traffic Server CDN configuration

CONFIG proxy.config.http.server_port INT 80CONFIG proxy.config.cache.ram_cache.size INT 512MBCONFIG proxy.config.url_remap.remap_required INT 1

map http://cdn.example.com/js http://js.example.comreverse_map http://js.example.com http://cdn.example.com/js

map http://cdn.example.com/css http://css.example.comreverse_map http://css.example.com http://cdn.exampe.com/css

map http://cdn.example.com/img http://img.example.comreverse_map http://img.example.com http://cdn.example.com/img

/dev/sd2

Common enemies of performance

TCP 3-way Handshake

Congestion avoidance

TCP Connection Management

Why Server Load Balancers?

Server Load Balancer

Executive Summary Understand your requirements

Evaluate available solutions

Building a CDN is easy

Apache Traffic Server is

- Fast and SMP scalable

- HTTP/1.1 compliant

- Battle hardened

- Easy to configure and operate

- Actively developed

- Free as in beer

trafficserver.apache.org