Apache Traffic Server HTTP Proxy Server on the

Apache Traffic Server HTTP Proxy Server on the Edge Leif Hedstrom Engineer leif@yahoo-inc. com zwoop@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 10 x normal usage, to deal with massive spikes. § 85, 000 requests / sec with small content out of cache, for a single (lab)box § 3. 6 Gbps out of a single box, with larger content (4 x Gig. E 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 Event-driven Y Y N N? Plugin APIs Y N Y part Y Y Forward Proxy Y N N Y Reverse Proxy Y Y Y Transp. Proxy N Y Y Y N N Load Balancer part Y! Y Y Y N Y Y ESI soon N N Y Y N ICP Y N N Keep-Alive Y N Y Y SSL Y N Y Pipeline Y N Y Cache

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 80 CONFIG proxy. config. cache. ram_cache. size INT 512 MB CONFIG proxy. config. url_remap_required INT 1 map http: //cdn. example. com/js reverse_map http: //js. example. com http: //cdn. example. com/js map http: //cdn. example. com/css http: //css. example. com reverse_map http: //css. example. com http: //cdn. exampe. com/css map http: //cdn. example. com/img http: //img. example. com reverse_map http: //img. example. com http: //cdn. example. com/img /dev/sd 2

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