Apache Traffic Server

Leif Hedstrom

Principal Architect, Akamai Technologies

lhedstro@akamai.com

zwoop@apache.org

@zwoop

History and introduction

Choosing a proxy

Setup

Origins of the software

Why HTTP proxy / cache?Better performance

Save money (or other scarce resources)

Make operations less of a pain in the …

Easier web development

Better user experience

Lets look at the three common HTTP proxy configurations

Forward Proxy

Reverse Proxy

Intercepting Proxy

Plenty of FOSS Proxy Servers

Choosing an intermediary

SMP Scalability and performance

Four Horseman of Bad Performance

Data copiesContext SwitchesMemory allocationLock contention

Avoid these!

http://pl.atyp.us/content/tech/servers.html

Traffic Server threads model

Event Processing

Disk cache: “Cyclone”

http://www.flickr.com/photos/gsfc/4461843139/

Some interesting featuresRAM: Optional compression

Various compression levels supportedVery fast (virtually no overhead using the faster

algo)

RAM: Several cache eviction algorithmsCLFUS algorithm avoids the classic problem on an

LRU during “scans”And it’s not encumbered by any patents

Disk: Supports various block sizes (e.g. SSD)

Disk: Can be tuned for various object sizes

Disk: No file system overhead (RAW disks)

Clustering

http://www.flickr.com/photos/vax-o-matic/2465358707/

Traffic Server performance

400,000 requests / sec in a production CDN50 Gbps / second (95-percentile)

Many more request handled for HTML

100,000 requests / sec with small content out of RAM cache, on a single (lab) quad-core

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

19Gbps on “localhost” using 2 CPUs (for large objects, 1MB in the test)

HTTP/1.1 Features

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 Y* 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 Y Y N 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

Ease of use, extensible

http://www.flickr.com/photos/stuartpilbrow/3345896050/

Traffic Server making Ops easyTraffic 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

Speaking of plugins, we have a very flexible plugin APIs for C/C++ developers (hopefully some scripted languages soon)

Stats and configurations are accessible via command line utilities

Configurations

plugin.config

records.config

volume.config

hosting.config

cache.config

update.config

ip_allow.config

storage.config

logs_xml.config

parent.config

remap.config

icp.config

records.config storage.config

remap.config

Critical in records.config

CONFIG proxy.config.exec_thread.autoconfig INT 1CONFIG proxy.config.exec_thread.autoconfig.scale FLOAT 2.0CONFIG proxy.config.exec_thread.limit INT 2

CONFIG proxy.config.http.server_port INT 8080

CONFIG proxy.config.http.cache.http INT 1CONFIG proxy.config.cache.ram_cache.size INT 512M

CONFIG proxy.config.reverse_proxy.enabled INT 1CONFIG proxy.config.url_remap.remap_required INT 1CONFIG proxy.config.url_remap.pristine_host_hdr INT 0

CONFIG proxy.config.ssl.enabled INT 0CONFIG proxy.config.ssl.server.cert.filename STRING server.pem

CONFIG proxy.config.url_remap.remap_required INT 1

CONFIG proxy.config.reverse_proxy.enabled INT 1

CONFIG proxy.config.url_remap.remap_required INT 0

CONFIG proxy.config.reverse_proxy.enabled INT 0

Content on the Edge

Traffic Server configurationCONFIG proxy.config.http.server_port INT 80CONFIG proxy.config.cache.ram_cache.size INT 4096MCONFIG 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

Enemies of Web performance

TCP 3-way Handshake

Congestion avoidance

TCP Connection Management

ATS Connection mgmt configurationCONFIG proxy.config.http.server_port INT 80CONFIG proxy.config.cache.ram_cache.size INT 0CONFIG proxy.config.url_remap.remap_required INT 1

CONFIG proxy.config.http.send_http11_requests INT 1CONFIG proxy.config.http.share_server_sessions INT 1CONFIG proxy.config.http.server_max_connections INT 2000

CONFIG proxy.config.http.keep_alive_no_activity_timeout_out INT 60CONFIG proxy.config.http.transaction_no_activity_timeout_out INT 60

map http://www.example.com/ http://real-www.example.com

Executive SummaryUnderstand your requirements

Evaluate available software, services and solutions

Apache Traffic Server is

Fast and SMP scalable

Battle hardened

HTTP/1.1 compliant

Easy to configure and manage

Extensible

Actively developed

And of course, it’s free!

Content Delivery: Correctness first

The concurrency problem

Solution 1: Multithreading

Problems with multi-threading