"Speed has never killed anyone" - Varnish, a HTTP accelerator

Varnish, a HTTP accelerator

SPEED HAS NEVER KILLED
ANYONE

Zentrum für Informations- und Medienverarbeitung
Dipl.-Ök. Christian Nölle

CHRISTIAN NÖLLE


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Degree
Self-employed
Scientific assistant
University
Living

VARNISH =
(HTTP|WEB)
(PROXY|ACCELERATOR)


No worries! Our setup is fast!
We‘ve got speed!


How much can it handle?


10 Req/s?

50 Req/s?

500 Req/s?
687 Re…
100 Req/s?

Source: Peter Suneson, http://www.sxc.hu/profile/CMSeter


SUDDENLY BECOMING
STATIONARY, THAT'S WHAT GETS
YOU.
Jeremy Clarkson


?
No


Yes

FAIRLY MODERN PIECE OF SOFTWARE
Varnish works on 32-bit, but was designed for

64bit. It's all about

virtual memory: Things like stack size suddenly matter on
32bit. If you must use Varnish on 32-bit, you're somewhat on your own.
However, try to fit it within 2GB. I wouldn't recommend a cache larger than
1GB, and no more than a few hundred threads... (Why are you on 32bit
again?) In order for you to install Varnish you

must have the

Linux - FreeBSD – Solaris and
root access Varnish can be installed on other UNIX systems as
following:

well, but it is not tested particularly well on these platforms. Varnish is, from
time to time, said to work on: 32 bit versions of the before-mentioned
systems. OS X NetBSD OpenBSD

GET IT UP AND RUNNING
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Put your cache in memory
Put
Your
Cache
In
Memory
If not applicable: Buy more memory!
If not applicable: Put it on disk, for God„s sake!
Let it listen to port 80
Change DNS of Domain to varnish server


FIRE IT UP!
varnishd -f /etc/varnish/my.vcl -s malloc,1G
-T 127.0.0.1:2000 -a 0.0.0.0:80
-f /etc/varnish/my.vcl
Where is my configuration file?
-s malloc,1G
What kind of cache storage and how big is it?
-T 127.0.0.1:6082
Text-administration interface. Listening on?
-a 0.0.0.0:80
Listen on port 80 for all HTTP requests

ANY CONFIG?
Sure! Minimum config needed at installation time:
 Define your backend server!
Use it with -f /etc/varnish/myown.vcl at startup time
Write it with Varnish Configuration Language = VCL


VCL
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Defines caching rules
Gets parsed, compiled and linked against varnish
Default VCL is always included after your rules!
Keep it simple! Focus on caching policy subroutines!


SUBROUTINES
vcl_recv
vcl_pipe
vcl_hash

vcl_pass
vcl_miss

vcl_hit

vcl_deliver


vcl_fetch

HIT
vcl_recv
vcl_pipe
vcl_hash

vcl_pass
vcl_miss

vcl_hit

vcl_deliver


vcl_fetch

MISS
vcl_recv
vcl_pipe
vcl_hash

vcl_pass
vcl_miss

vcl_hit

vcl_deliver


vcl_fetch

PASS
vcl_recv
vcl_pipe
vcl_hash

vcl_pass
vcl_miss

vcl_hit

vcl_deliver


vcl_fetch

PIPE
vcl_recv
vcl_pipe
vcl_hash

vcl_pass
vcl_miss

vcl_hit

vcl_deliver


vcl_fetch

ALL UP AND RUNNING, BUT…

Easy! Cache is too small!
Source: Bob Smith, http://sxc.hu/browse.phtml?f=profile&l=brainloc

Varnish will, in the default configuration, not cache a object coming from
the backend with a Set-Cookie header present. Also, if the client sends
a Cookie header, Varnish will bypass the cache and go directly to the
backend.

BEWARE OF COOKIES!


TYPO3 always sends a cookie: fe_typo_user
Even if not needed
Or only needed for certain parts of the site; e.g. login

TYPO3 AND COOKIES


Know your content!
Know your installation of TYPO3!
Know your bad hacks!

BY THE WAY: YOU GOT ANY
CLUE OF THE WEBSITE, YOU’D
LIKE TO CACHE?

WHAT TO DO WITH COOKIES?
First of all: Depends on your setting! Investigate!
Numerous possibilities, some of them:
 Use an extension (moc_varnish, cachinfo, varnish, vcc…)
 Unset cookies in VCL, allow only where needed!
 You don‟t need the fe_typo3_user cookie at all?
– $TYPO3_CONF_VARS['FE']['dontSetCookie'] = 1


Let‟s see the real stuff!

DIG DEEPER!


backend default {
.host = "12.34.56.78";
.port = "80";
.probe = {
.url = "/probe.txt";
.timeout = 1s;
.interval = 3s;
.window = 10;
.threshold = 5;
}
}
PROBE YOUR BACKEND SERVERS ON HEALTH!
Some real world VCL examples

director test round-robin {
{ .backend = server1; }
{ .backend = server2; }
{ .backend = {
.host = "12.34.56.78";
.port = "82";
}
}
}

DEFINE DIRECTORS

sub vcl_recv {
if (req.backend.healthy) {
set req.grace = 30s;
} else {
set req.grace = 1h;
}
}

GRACE MODE: DELIVER AN OLD OBJECT

sub vcl_fetch {
if (beresp.http.cache-control ~ "(no-cache|private)" ||
beresp.http.pragma ~ "no-cache") {
set beresp.ttl = 0s;
# Make sure that We remove alle cache headers, so the Browser does
# not cache it for us!
remove beresp.http.Cache-Control;
remove beresp.http.Expires;
remove beresp.http.Last-Modified;
remove beresp.http.ETag;
remove beresp.http.Pragma;
return (deliver);
}
}

RESPECT “NO CACHE” SETTING FROM BACKEND

WHAT ELSE DO WE DO?
 Device detection
 Lifetime manipulation – if requested more often, lifetime in
cache gets prolonged
 Let internal network purge an object with STRG + F5 from
browser
– But only when backends are healthy!

 Cache all images, css, js a.s.f. for at least one week
 Saint mode to deal with strange content from backend
 Mix up different sources in “one” website


START IT RIGHT:
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Find out about your website
Go for varnish package, not source!
Keep your VCL simple
Monitor your varnish
– Use the tools provided (varnishstat, varnishlog varnishhist)
– Keep an eye on syslog/messages
– Munin / Cacti

 Tune only when there is a problem. Do not overfix!


WHEN YOU HAVE DONE IT RIGHT:


And remember:

SPEED HAS NEVER KILLED
ANYONE


Mail: noelle@uni-wuppertal.de

TWITTER: @STBC


"Speed has never killed anyone" - Varnish, a HTTP accelerator

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