HTTP accelerator
Cachos 2.0
Luis Henrique Okama
Tollef Fog Heen
Mario Carvalho

What is the problem?
GET / HTTP/1.1
Hang on, I need to look up a few hundred things in my
database and then do a lot of editing controlled by a
scripting language
HEAD / HTTP/1.1
Hang on, I need to look up a few hundred things in my
database and then do a lot of editing controlled by a
scripting language, and then I will throw the result
away.

Why are CMS-es slow?
Complex content generation process
Single database prevents clustering
Expensive software ditto
This means: we need server side caching

Why are the existing solutions not good enough?
Squid, ancient design, forward proxy
Apache, not what it's built for, not what it's good at
Akamai (and similar), expensive, vendor lock-in

What is Varnish?
Dedicated HTTP accelerator
Focus on server-side speedups
Policy control
High performance
Varnish Configuration Language
Shared memory log

High performance
11 syscalls + 7 locks for a cache hit
Work with the OS, not against it.
Multi-CPU, multi-core
64 bit
Use advanced OS features:
Accept filters
madvise(MADV_RANDOM)
kqueue, epoll
Don't copy data if you don't have to
Use workspaces, not malloc/free
Compiled configuration

Policy control
Override TTLs
Add, remove or change headers
Strip cookies
Rewrite URLs
Invalidate objects in the cache

Varnish Configuration Language
Simple domain specific language
Compiled via C language to binary
Transparently!
Dynamically loaded
Multiple configs loaded concurrently
Instant switch from one VCL to another.
Can be done from VCL

VCL Example
acl some_acl { "10.0.0.0/8" }
if (client.ip ~ some_acl) {
pass;
}
if (req.http.host ~ "foo.com$") {
set req.http.host =
regsub(req.http.host,
"foo.com", "bar.org");
}
if (obj.valid) {
set obj.ttl = 10m;
deliver;
}

Shared memory logfile
Fast
Custom log tailers
varnishtop
varnishlog
varnishhist
varnishncsa
varnishstat

Globo.com cache infrastructure

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Comparative
scalability
setup time
cost
open source
throughput
physical space

Some data

Conclusion
software customization
work set

Real life performance

Questions

Contacts
Luis H. Okama
okama@corp.globo.com (www.globo.com)
Mario Carvalho
mariocar@corp.globo.com (www.globo.com)
Tollef Fog Heen
tfheen@redpill-linpro.com (www.varnish-cache.com)
@ Stand Globo.com