Varnish is a reverse proxy that can cache pages to improve Drupal performance. It works with Edge Side Includes (ESI) to cache parts of personalized pages. With ESI, the first page requires two requests but subsequent pages only need one request each. Benchmarking tools can measure performance. Configuring Varnish and ESI requires modifying Drupal, installing modules, and editing Varnish configuration files. Speed gains depend on caching strategy and workload.

1. VarnishBOF!

2. What's this talk about?A basic intro to Varnish and reverse proxiesSome cool ESI stuffHow to setup, implement + configure Varnish/ESI in DrupalTeh Awesomeness of speed

3. Why Varnish?

4. Drupal performs…just…

5. How much faster?Drupal20 reqs/sec?Varnish200 reqs/sec?

6. When personalisation goes wrong

7. Dries logs in

8. Drupal creates a personalised pageLogged in as dries

9. The page gets cachedVarnish

10. When webchick hits the site

11. The page is fetched from the cacheVarnish

12. The personalisation is incorrectLogged in as dries

13. WTF?WTF?

14. No-cache headers can prevent thisVarnish

15. But now it's slow :-(

16. EdgeSideIncludes

17. ESI: Tales from the pastThe idea originated in SSISSI, but moved to the edgeESI is a W3C standardESI is a bunch of xml tags/attributes.Supported by:Varnish (partial support – no ESI variables)AkamaiSome Nginx support???

18. Dries is visiting the site

19. The page is requestedVarnishhttp://example.com/node/1

20. The page includes an ESI tag<esisrc= "http://example.com/esi/user/0" />

21. The proxy sends a second requesthttp://example.com/esi/user/0Varnishhttp://example.com/node/1

22. The ESI URL sends a HTML snip<div id="userinfo"> <a title="View &amp; edit your user profile">Logged in as dries</a> <a href="/logout">Logout</a></div>

23. The ESI code is merged with the page

24. Proxy forwards the page onhttp://example.com/esi/user/0Varnishhttp://example.com/node/1

25. This doesn’t sound quicker

26. The Importance of TestsIt's important to measure the results(I'll come to measuring tools later!)The ESI snippets can be cached too

27. Cached ESIs

28. 1st Page = 2 Requestshttp://example.com/esi/user/0Varnishhttp://example.com/node/1

29. 2nd Page = 1 requestVarnishhttp://example.com/node/2

30. 1 request for each new page10 pages = 11 requestsEach page is cachedThe ESI tag is cached

31. The next visitor gets the page for freeVarnishPage fetched from cachehttp://example.com/node/1

32. 1st page = 1 request (for the ESI)http://example.com/esi/user/0VarnishPage fetched from cachehttp://example.com/node/1

33. Following pages all served from cacheVarnish

34. 1 request for each new page10 pages = 11 requestsThe ESI tag is cachedEach page is cachedSubsequent requests have 1 request for the ESI tag20 pages = 12 requests (10 pages + 2 ESI tags)

35. Fast enough yet?Warm the cache

36. A modern infrastructureVarnishHA ProxyTehIntertubesService webheadadmin/cron/emails/??

37. Spidering the siteVarnishHA ProxyTehIntertubesLink-checker /spider app.Service webheadadmin/cron/emails/??

38. Dries is back for more

39. Each user generates 1 requesthttp://example.com/esi/user/0VarnishPage fetched from cachehttp://example.com/node/1

40. 5 users, 40 pages5 backend requests!

41. Theory Over

42. Basics Varnish+Drupal

43. Installing Varnishsudo apt-get install varnishsudo yum install varnishEdit /etc/default/varnishEdit /etc/varnish/default.vclUsual config:Varnish listens on port 80Apache listens on port 8080 (or any available port)SSL is more complex – sometimes Pound is used for SSL decryption

44. VCLs are awesome!Varnish configuration is controlled by VCL: Varnish Configuration Language.Documented athttp://www.varnish-cache.org/trac/wiki/VCLDrupal VCL examples can be found in:Mercury (Amazon AMI)ESI moduleYou can write C code in VCLs. Oh my.

45. Keeping the cache currentVarnish admin portVarnish

46. Varnish Management PortThe Varnish admin port uses a plain-text protocol to command VarnishTest by:telnet localhost 6093List commands by typing helpPurge cached pages: url.purge <regexp>E.g. url.purge .*The Varnish module provides an API.

47. Use with caution!The default behaviour of the Varnish module is toclear the entire cachewhen you edit a node.

48. Enter…the Expires moduleCame from the Boost moduleClears specific cache pages – not the entire cacheSupports path-alias URLs as well as node/1 paths.Provides hook_expire_cache_alterto add URLs (e.g. nodes displayed in a page-view)Supports other cache modules, not just Varnish.

49. I can haz ESI?The ESI module provides block integration

50. Configuring ESIDownload the moduleConfigure the blocks to serve via ESI, and their TTLModify the Varnish VCL (the ESI module comes with example VCLs to useComing soon:D7Panels integration

51. BenchmarkingSome tools:J-meterab (apache-benchmark)SeigeApproaches:Hammer your URL(s)ab –n 100 –c5 http://example.com/Replay your log files

52. Pitfalls awaitVCLs are complexPer-user cache rules are even scarier!Varnish may be slowerRisk exposing private data

53. AlternativesBoost moduleNo need to install a new service on the serverStatic file cacheAdvanced cache moduleAuthcache moduleOther proxies:SquidNginxAkamai?

54. Summary

55. How hard?

56. VarnishVarnish moduleExpire moduleESI moduleTeh Awesomeness

57. Thanks!Marcus Deglose: marcus@deglos.comt: @manarthirc: manarth

58. Picture creditsThanks to these CC-licencedflickr usersMac Book Pro - http://www.flickr.com/photos/wicho/F1 car - http://www.flickr.com/photos/w3i_yu/Banger car - http://www.flickr.com/photos/photoplodDries - http://www.flickr.com/photos/borisDries+laptop - http://www.flickr.com/photos/azugaldiaWebchick - http://www.flickr.com/photos/mortendkWebchick - http://www.flickr.com/photos/pureginFire - http://www.flickr.com/photos/benwattsHourglass - http://www.flickr.com/photos/opendemocracyStopwatch - http://www.flickr.com/photos/purplemattfish