Cache Rules Everything Around Me
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My presentation about WordPress and caching from WordCamp Baltimore 2013. See it with funny animated GIFs at http://kingkool68.com/wp-cream/ Fork my slides on GitHub https://github.com/kingkool68/WP-Cache-Rules-Everything-Around-Me
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Cache Rules Everything Around Me
- 5. HI, I'M RUSSELL HEIMLICH (Heimlich, like the maneuver) Head Cache Invalidator at the Pew Research Center
- 8. 2006 - 2009 I worked at USNews & World Report
- 11. ON LAUNCH DAY WE ALWAYS SEE A HUGE TRAFFIC SPIKE But one year we got lucky…
- 12. The marketing/biz dev team managed to get us featured on the homepage of a major web portal! (And by featured I mean the featured story on their homepage)
- 13. WE WERE GOING TO BE FEATURED ON… (Before their CEO discovered Adobe Illustrator)
- 14. WE WERE EXCITED!
- 15. Ok maybe we looked more like this…
- 16. The story went live on Yahoo.com and we watched…
- 17. The servers started getting slower…
- 18. Editors were calling us saying they couldn't get in to the admin area…
- 19. Our servers were completely down…
- 20. We had to call Yahoo! and have them remove the story because we couldn't handle the traffic…
- 23. P.S. Don't feel bad for USNews
- 24. WHAT IS CACHING?
- 25. CACHE “a component that transparently stores data so that future requests for that data can be served faster.” — via Wikipedia, Cache (Computing)
- 26. A cache may contain values computed earlier or duplicate values stored elsewhere.
- 27. A cache hit can complete the request by reading the value from the cache.
- 28. A cache miss has to be recomputed or fetched from another location which is much slower.
- 29. The more requests that can be served from a cache, the faster the system performs. The faster the system, the more requests it can handle.
- 30. A REAL-WORLD EXAMPLE You're taking 5 classes and need to write 5 essays…
- 31. You could write 5 separate essays OR You could write one essay and use it for all of your classes
- 32. THAT'S CACHING!
- 33. There are many (potential) layers of caching involved in a single web request.
- 35. A BASIC REQUEST
- 36. A BASIC REQUEST
- 44. HTTP HEADERS
- 45. “The easiest request to serve is the one never sent at all.” I just made this quote up.
- 46. Your logo image isn't going to change when going from your homepage to a single blog post… So why make the browser even request it?
- 47. FAR FUTURE EXPIRES HEADER Tell the browser how long the copy of the file is valid Cached files that are valid are not re-downloaded from the server
- 48. WHAT DOES THAT LOOK LIKE? Add this to your file:.htaccess <ifmodulemod_expires.c=""> ExpiresActiveon ExpiresDefault "accessplus1month" ExpiresByTypeimage/gif "accessplus1month" ExpiresByTypeimage/jpeg "accessplus1month" ExpiresByTypeimage/png "accessplus1month" </ifmodule>
- 49. The HTML5 Boiler Plate project's .htaccess file Read the docs View the source
- 50. BUT WHAT IF THE IMAGE/JS/CSS FILE CHANGES? The browser will keep loading the resource from it's local cache
- 51. > And then you have to clear the browser cache or hard refresh the page (Shift + Refresh).
- 52. WE NEED CACHE-BUSTING FILENAMES! WordPress' and supports this wp_enqeue_script() wp_enqueue_style() wp_enqueue_script($handle,$src,$deps,$ver,$in_footer); wp_enqueue_style($handle,$src,$deps,$ver,$media); which outputs a script like this my-super-neato-script.js?ver=3.6.1 my-trendy-styles.css?ver=3.6.1
- 53. But then every time you update your JavaScript or CSS you need to change the $vervariable to bust the cache…
- 54. SO I WROTE A PLUGIN CDN Friendly CSS and JS URLs in WordPress /theme/css/2013-09-12_5:21/my-style.css maps to /theme/css/my-style.css
- 55. CDNS
- 56. CONTENT DELIVERY NETWORKS (CDNS) Set of servers in multiple data centers around the world to serve content with high availability and performance.
- 57. CDNs serve their copy of a file, if available, sparing your server from the traffic.
- 58. If the CDN doesn't have a copy of the file, it passes the request back to the origin.
- 59. TWO TYPES OF CDNS 1. Push - assets get uploaded to the CDN manually, you link directly to it 2. Pull - The CDN is a proxy saving requests that are passed through it See Push vs. Pull CDNs
- 60. DNS CHANGES NEEDED FOR PULL CDNS cdn.example.com masks ugly CDN URL (CNAME)
- 61. DNS CHANGES NEEDED FOR PULL CDNS example.com points to origin IP Address (A Record)
- 62. The CDN uses the Expires header to determine if cached asset is stale or not. Stale requests get passed to the origin server
- 63. Some CDNs and proxies . So avoid it if you can. don't cache URLs with a query string BAD http://www.example.com/js/file.js?2013-09-12 GOOD http://www.example.com/js/2013-09-12/file.js http://www.example.com/js/file.2013-09-12.js
- 64. If you cache your HTML via a CDN then if your origin server goes down your site will still be served. Visitors won't even know.
- 65. Distributing content across the world, visitors will download from a server closer to them.
- 68. Full page caching takes the result of a page request from WordPress and saves it as a static HTML file that will be served up the next time.
- 69. This reduces the load on PHP and MySQL
- 70. CACHING PLUGINS (Advandced, lots of options) (Easier set-up) (Multi-server environment) (For low-resource hosts) W3 Total Cache WP Super Cache Batcache Hyper Cache
- 71. CACHING PLUGIN TIPS Don't cache pages for logged in users Don't cache POST requests Do serve cached files from mod_rewrite(not PHP) Don't serve a separate mobile version (use responsive design) Make sure it is working!
- 72. PHP CACHING
- 74. TRANSIENTS API Used to store data that can expire at any time Has an expiration to invalidate the data Uses the wp_options table or an object cache See http://codex.wordpress.org/Transients_API
- 76. MULTISITE TRANSIENTS API FUNCTIONS set_site_transient() get_site_transient() delete_site_transient()
- 78. TIME CONSTANTS As of WordPress 3.5 several constants were introduced to easily express time MINUTE_IN_SECONDS =60(seconds) HOUR_IN_SECONDS =60*MINUTE_IN_SECONDS DAY_IN_SECONDS =24*HOUR_IN_SECONDS WEEK_IN_SECONDS =7*DAY_IN_SECONDS YEAR_IN_SECONDS =365*DAY_IN_SECONDS
- 79. TRANSIENTS API IS IDEAL FOR… Fetching RSS feeds Storing an external API call Caching a complex query ANYTHING that needs to expire at some time
- 80. WP OBJECT CACHE WordPress' internal class for caching data. See http://codex.wordpress.org/Class_Reference/WP_Object_Cache
- 81. CACHING PERSISTANCE WP_Object_Cache data isn't saved between page requests by default. If an object cache is available, WP_Object_Cache will use that instead
- 82. WP_CACHE FUNCTIONS Don't call WP_Object_Cache Class directly! wp_cache_add($key,$data,$group,$expire); wp_cache_set($key,$data,$group,$expire); wp_cache_get($key,$group='',$force=false,$found=null); wp_cache_delete($key,$group); wp_cache_replace($key,$data,$group,$expire)
- 84. OBJECT CACHING
- 85. WHAT IS OBJECT CACHING? Distributed, in-memory key-value store for small chunks of data. (not distributed) Memcached Redis APC
- 86. UH… IN ENGLISH? Store Transients API and WP Object Cache items in memory between requests Make it available to multiple servers RAM is way faster than disk!
- 87. HOW DO I ENABLE OBJET CACHING? 1. Download and install or or on your server 2. Add the appropriate object-cache.phpfile to your wp- content folder Memcached Redis APC See: or or Memcached Object Cache Plugin WordPress Redis Backend APC Object Cache Backend
- 88. OPCODE CACHING
- 89. WHAT DOES OPCODE CACHING DO? PHP is written in a human-readable syntax When run, PHP is compiled to opcode that a computer understands An opcode cache speeds up the execution of PHP
- 92. OPCODE CACHES Alternative PHP Cache (APC) eAccelerator XCache Zend Optimizer+
- 93. WHICH OPCODE CACHE TO USE? Zend Optimizer+ will be bundled with PHP 5.5 See http://halfelf.org/2013/trading-apc-for-zend/
- 94. BENCHMARKS PHP (No Opcode Cache) ~40 APC ~260 Zend Optimizer + ~307 Number of Requests per second See http://www.ricardclau.com/2013/03/apc-vs-zend-optimizer-benchmarks- with-symfony2/
- 95. MYSQL CACHING
- 96. MYSQL'S QUERY CACHE Cache's result for frequently used SELECTstatements Any INSERT, UPDATE, or DELETEstatement flushes the query cache See MySQL Query Cache Documentation
- 97. TO SUMMARIZE
- 98. Leverage browser caching via HTTP headers Use a CDN if you can or a full-page caching plugin WordPress' caching APIs are helpful Set-up object caching on your server Utilize an opcode cache to speed up PHP Make sure MySQL's query_cacheis turned on
- 99. MORE READING 1. by Zack Tollman 2. by Joseph Scott 3. by Ryan Burnette 4. by WordPress.com VIP 5. by Erick Hitter 6. by Scott Taylor Core Caching Concepts in WordPress Scaling WordPress WordPress Fragment Caching Revisited Caching Caching, Scaling, and What I've Learned Programming for WordPress.com VIP WordPress + Memcached
- 100. IN CONCLUSION