Running with Scissors - RTÉ's path to caching in Varnish I share how Varnish became RTÉ's preferred method for caching. I also walk attendees through how things are getting easier and more complex at the same time with Varnish, and why it is important to know what your systems are doing.

1. Running with Scissors
RTE.ie’s path to caching in Varnish
Varnish Summit London 10th April 2014
John Moylan - http://8t8.eu

2. RTÉ Digital

3. PLATFORMS

4. Started working with RTÉ.ie in 1999
The internet was a very different place

5. In the beginning there was squid

6. Squid V. Varnish
Lessons learned

7. Then there was Varnish
Ram doesn’t
come in 64MB
sticks anymore.

8. Then there was Varnish
Bandwidth isn’t
counted in Mb/s
anymore
● 2001 10Mb’s
● 2014 40Gb/s
excluding CDN
409,600% Increase

9. The great thing about mod_rewrite is it gives you all
the configurability and flexibility of Sendmail. The
downside to mod_rewrite is that it gives you all the
configurability and flexibility of Sendmail.''
-- Brian Behlendorf
Apache Group
With Great Power Comes Responsibility

10. The great thing about VCL is it gives you all the
configurability and flexibility of Sendmail. The
downside to VCL is that it gives you all the
configurability and flexibility of Sendmail.''
-- John Moylan
RTÉ Digital
With Great Power Comes Responsibility

11. Scope
#don't cache ajax requests
if (req.http.X-Requested-With ==
"XMLHttpRequest") {
return (pass);
}
Whoops! Scope

12. Scope
# don't cache authenticated sessions
if (req.http.Cookie && req.http.Cookie ~
"(wordpress_|PHPSESSID)") {
return(pass);
}
Whoops Scope

13. Lessons learned
1. Scope special conditions properly
2. GET’s and HEADS no longer work
for checking cache issues
Third party web app developers:
Please don’t break the web
GET’s should not have side effects
(and while I’m on my soapbox, please
use proper status codes)

14. Old School Monitoring
RRDTool
RPS,
Bandwidth,
pagefaults,
Hit Ratio,
FD’s, CPU, Memory
Grep’ing, cut’ing, sort’ing origin server logs
Plus GET’s are normally GET’s. Cache is
dumb

15. Varnish Monitoring
VCS
VAC
Varnishlog
Varnishstat
Newrelic
PyVarnish

16. Varnish Monitoring
PyVarnish
https://github.com/redsnapper8t8/pyvarnish

17. Thanks for listening
Questions?