When high performance on a web application is a hard requirement Varnish can be of rescue. But does it’s name, the high-performance HTTP accelerator, really bring what you expect? What are the caveats, pitfalls and problems you introduce when developing your application when the released version is only able to run when there is a Varnish in front? This session will give you some answers, tips and tricks to aid in application design, development with PHP and solutions when there is no Varnish in front of your application.

1. Varnish, the high performance valhalla? JEROEN VAN DIJK 29 JANUARY 2011

2. ABOUT ME Jeroen van Dijk CTO @ Enrise Email: jeroen@enrise.com @neorey on twitter Infected by open source…

3. WHAT IS VARNISH? (1) HTTP Accelerator Caching reverse proxy Load balancer Fail over system NOT a webserver!

4. WHAT IS VARNISH? (2) Originally built for a Norwegian newspaper > 545K new hostnames in December 2010 Netcraft monthly survey Known users Wikileaks Facebook Twitter Massive growth in usage

5. WHAT IS VARNISH? (3) Designed for 64 bit architecture Highly scalable Varnish in front of other Varnish(es) Perfect browser cache solution Prevent hard refresh calls Scaling limits currently unknown

6. IMPLEMENT VARNISH (1) Simplest no proxy configuration

7. IMPLEMENT VARNISH (2) Simplest proxy configuration

8. INTERNALS (1) Possible request paths

9. INTERNALS (2) Optimal request path

10. INTERNALS (3) Caching request path

11. INTERNALS (4) Prevent caching

12. INTERNALS (5) Bypassing Varnish

13. INTERNALS (6) Errors or issueing restarts

14. VARNISH CONFIGURATION LANGUAGE(1) 9 subroutines (vcl_recv, vcl_hash, etc…) Backend(s) Access Control Lists Directors (random, round-robin) Custom subroutines Inline C Compiled to C when run

15. VARNISH CONFIGURATION LANGUAGE(2) if (req.request == "GET" && req.url ~ "(gif|jpg|jpeg|bmp|png|ico)$") { unset req.http.cookie; set req.grace = 1m; return(lookup); } Cache images in vcl_recv

16. VARNISH CONFIGURATION LANGUAGE(3) if (req.http.cookie) { set req.http.Cookie = regsuball(req.http.Cookie, "__utm.=[^;]+(; )?", ""); if (req.http.cookie ~ "^ *$") { remove req.http.cookie; } } Remove Google Analytics in vcl_recv

17. VARNISH CONFIGURATION LANGUAGE(4) backend default { .host="192.168.1.10"; .port="8080"; } backend second { .host="192.168.1.20"; .port="8080"; } Multiple backend configuration

18. VARNISH CONFIGURATION LANGUAGE(5) director balance random { { .backend = default; .weight = 1; } { .backend = second; .weight = 2; } } sub vcl_recv { set.req.backend = balance; return(pass); } Load balanced 33/66 % config

19. VARNISH CONFIGURATION LANGUAGE(6) if (obj.hits > 0) { #if hit add hit count set resp.http.X-Cache = "HIT-" obj.hits; } else { set resp.http.X-Cache = "MISS”; } Adding headers on response

20. VARNISHING WORDPRESS (1) Siege on WordPress homepage No Varnish Default Varnish installation Custom VCL configuration

21. VARNISHING WORDPRESS (2) No Varnish

22. VARNISHING WORDPRESS (3) Default Varnish

23. VARNISHING WORDPRESS (4) # Drop any cookies sent to WordPress. sub vcl_recv { unset req.http.cookie; } # Drop any cookies WordPress tries to send back sub vcl_fetch { unset beresp.http.set-cookie; } Kill those cookies!

24. VARNISHING WORDPRESS (5) Custom Varnish

25. TOOLS Varnishstat Varnishsizes Varnishlog Varnishtop Varnishadm Varnishhist You can’t go without!

26. VARNISHSTAT Live statistics of a running varnish Interesting keys Client_req Cache_hit Cache_miss S_req S_bodybytes Uptime

27. VARNISHSTAT Also available as XML output

28. VARNISHSIZES Pipe = hit, Hash = miss

29. VARNISHLOG Request of gif image by client

30. VARNISHLOG Log misses varnishlog –i TxURL Log hits varnishlog –o VCL_Call hit | grep RxURL This is a live log, not reading from file

31. EDGE SIDE INCLUDES (1) Markup language Co-authored by Akamai, IBM, Oracle & more Extensive features Varnish implements only one! <esi:include src=“uri” /> Very powerful for content assembly

32. EDGE SIDE INCLUDES (2) if … else <esi:choose><esi:when> … <esi:otherwise> Variables <esi:assign> and <esi:vars> Examples? http://esi-examples.akamai.com/

33. EDGE SIDE INCLUDES (3) if (req.url ~ "^/url/to/esi/snippets") { unset beresp.http.set-cookie; } ## enable esi on header from backend if (beresp.http.enable-esi == "1") { esi; unset beresp.http.enable-esi; } VCL config for ESI

34. EDGE SIDE INCLUDES (4) Where are the ESI’s?

35. EDGE SIDE INCLUDES (5) Possible request paths

36. CASE AUTOTRACK.NL (1) Second hand car site running Varnish

37. CASE AUTOTRACK.NL (2) > 40 million pageviews a month >500k search requests between 8-10pm Powered by Varnish Zend Server Solr Oracle Built with 5 developers using Zend Framework 2 developers working on frontend logic

38. CASE AUTOTRACK.NL (3) Problem for a frontend developer

39. CASE AUTOTRACK.NL (4) Developing without Varnish ESI tags are not parsed Incorrect user interface Varnish is POSIX only

40. CASE AUTOTRACK.NL (5) Custom ZF view helper, called by $this->esi(‘uri’) protected static $_headerSent = false; public function esi($uri) { if(false === self::$_headerSent) { $front = Zend_Controller_Front::getInstance(); $response = $front->getResponse(); $response->setHeader('enable-esi', 1); self::$_headerSent = true; } return ‘<esi:include src="' . $uri . '"/>’; }

41. CASE AUTOTRACK.NL (6) Custom ZF controller plugin to the rescue Replace body content on dispatchLoopShutdown Cache the snippets like Varnish would do Respect Cache-Control TTL Functional testing of site during development

42. CASE AUTOTRACK.NL (7) ZF controller plugin hooks

43. CASE AUTOTRACK.NL (8) $hash = hash(‘md5’, $data); $regex = ‘~<esi:include src="(.+?)"[ ]*/>~s’; if (preg_match_all($regex, $data, $esiTags, PREG_SET_ORDER) > 0) { foreach($esiTags as $esiTag) { $content = $this->_replaceEsi($esiTag[1]); $data = str_replace($esiTag[0], $content, $data); } } if ($hash != hash(‘md5’, $data)) { return … recurse this method…; // more ESI’s to replace } return $data; Called on dispatchLoopShutdown

44. CASE AUTOTRACK.NL (9) … $fp = fopen($uri, 'r', false, $this->_getHttpContext()); if (false !== $fp) { $data = stream_get_contents($fp); $meta = stream_get_meta_data($fp); foreach ($meta['wrapper_data'] as $header) { if (preg_match('~Cache-Control: max-age=(+)~', $header, $match)){ if (false !== $data) { $cache->save($data, $key, array(), intval($match[1])); break; } … Replace ESI, if not found in cache

45. CASE AUTOTRACK.NL (10) Success!

46. CAVEATS Not very suitable for 32bit Beware of cookie monsters Minimize cookie usage in ESI No compression support when using ESI No SSL support

47. QUESTIONS? Rate my talk http://joind.in/2415 Reach me @neorey jeroen@enrise.com Enrise PHP TestFest – 21st of February

48. THANKS!

49. RESOURCES (1) http://news.netcraft.com/archives/2010/12/01/december-2010-web-server-survey.html http://onaxer.com/blog/2010/11/09/varnish-configuration-language-vcl/ http://blogs.osuosl.org/gchaix/2009/10/12/pressflow-varnish-and-caching/ http://kaanon.com/blog/work/making-wordpress-shine-varnish-caching-system-part-1 http://www.varnish-cache.org/trac/wiki/

50. RESOURCES (2) http://www.akamai.com/html/support/esi.html http://kristianlyng.wordpress.com/2010/01/26/varnish-best-practices/