Varnish for web developers
| Author | Kacper Wysocki |
| Contact | |
| Date | November 24, 2010 |
I already have $CACHE. Why Varnish?
sweet architecture
really REALLY high loads
flexible control and transparency
can make things more secure too
There are no silver bullets
Usually we use varnish to:
scale a website
fix header stuff
hack around application issues
Logistics
setup varnish
apt-get install varnish yum install varnish
NEED Varnish 2.x
WANT Varnish 2.1
watch out for the 32 bits
features covered
what to cache
how to cache
purging pages
edge side includes
side note: backend definition
do this now:
backend mine {
.host = "my backend";
.port = "80";
}
what to cache
EVERYTHING!
Cache-control: public, max-age=180
Cache-control: public, smax-age=300, max-age=180
must-revalidate ; no-cache
what to cache cont'd
Last-Modified + Expires
Age:
Pragma: no-cache
Etags hash
how to cache
avoid cookies
delete cookies
send reasonable header => automagic!
browser cache too!
What about...
identify static content
/css, /js, /images, /static etc
what dynamic pages can be cached?
NEVER cache another man's content
avoid redirects :-P
Purging pages
there are two hard problems in CS
lazy, so-called "bans"
purge on url, header, other conditions
deletes from cache
Purging pages cont'd
telnet, purge_url
HTTP PURGE + acl
GET /foo/bar?purge=true
cache-channels
fix your app to expire cache automagically!
purges: excersizeamples
purge req.url ~ "/foo"
purge req.http.user-agent ~ "Firefox" &&
obj.http.content-type ~ "text"
purge("req.url == " req.url);
Edge Side Includes
Benefits:
paste together sites
cache what can be cached
dynamic fragments of pages
same content (frame, img src,..) in many places
ESI cont'd
Limitations:
must be defined backend!
small subset of real ESI
no gzip, deflate, ssl (but fixable with nginx)
session workspace
Enable ESI
sub vcl_fetch {
if(obj.http.content-type ~ "text/html"){
esi;
}
}
Practical ESI
<html> <body> Foobar <esi:include src="http://kwy.u.bitbit.net/"> <esi:include src="/cgi-bin/date.cgi"> </body>
More ESI
<esi:include src="/must/be/reachable/thru/backends/"> <esi:remove>not shown if ESI on</esi:remove> <!--esi not shown if ESI is off -->
Questions?
kacper.blog.linpro.no
kwy.u.bitbit.net
6BD0 3F9C 5F77 AD24 F60A 86EC FD82 7E34 674A 506F
References: http://www.varnish-cache.org/trac/wiki