Cache Money Business

Mark Jaquith“JAKE-with”

@markjaquith mark@jaquith.me markjaquith.com

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$CA£ING@markjaquith #wcldn

Caching storing data for future use

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More Cache Fewer Problems

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Caching Principles

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DO LESS WORK

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DO LESS WORK

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WORK LESS OFTE

N

WORK LESS OFTEN

$TTL = 5400; $TTL = 900;

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MAKE GENERIC OUTPUT

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Cache the whole page

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Batcache

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W3 Total Cache

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WP Super Cache

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Varnish or Nginx

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CDN —

Content Distribution

Network

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Nginx Cache Purging

labs.frickle.com/nginx_ngx_cache_purge/

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location ~ \.php$ {

}

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set $no_cache_set 0;set $no_cache_get 0;

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if ( $http_cookie ~* "comment_author_|wordpress_(?!test_cookie)|wp-postpass_" ) { set $no_cache_set 1; set $no_cache_get 1;}

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# X-Nginx-Cache-Purge: 1# header will skip the cache!

if ( $http_x_nginx_cache_purge ) { set $no_cache_get 1;}

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fastcgi_no_cache $no_cache_set;

fastcgi_cache_bypass $no_cache_get;

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function nginx_purge_url( $url ) { wp_remote_get( $url, array( 'reject_unsafe_urls' => false, 'timeout' => 0.01, 'blocking' => false, 'headers' => array( 'X-Nginx-Cache-Purge' => '1' ) ));}

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add_action( 'transition_post_status', 'nginx_purge_post', 10, 3);

function nginx_purge_post( $new, $old, $post ) { if ( 'publish' === $old || 'publish' === $new ) {

nginx_purge_url( get_permalink( $post ) ); }}

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Variable cache lengths +

Proactive cache refreshing

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add_action( 'template_redirect', 'cache_home_page_length);

function cache_home_page_length() { if ( ! is_user_logged_in() && is_home() ) { header( 'Cache-Control: public, max-age=300' ); }}

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Logged in = no page caching?

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How does the page vary?

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1. Toolbar 2. Inline edit links 3. User's private posts 4. Moderated comments shown 5. Comment form

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Remove these things —OR—

Make them generic

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Comment form HIDE

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Toolbar GONE

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Inline edit links GONE

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User's private posts GONE

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Moderated comments GONE

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Compare:

10 editors and 1000 subscribers view 5 pages

each

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Caching skipped for logged in users:

5,050 dynamic views

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Caching skipped for Editors and up only:

50 dynamic views 5000 cached views

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Less than 1% of the workload as before!

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What if the page really DOES need per user

customization?

e.g. "Howdy $username"

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1. Load 2. Ajax if logged in 3. Customize

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Um… cookies

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1. Set JS-readable cookies 2. Get rid of the normal

ones 3. Populate the form with

JavaScript

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Good news…

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Cache Buddy github.com/markjaquith/cache-buddy

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Cache WordPress

Objects

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APCu (single server only)

— Memcache

— Redis

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APCu WordPress.org/plugins/apc

— Memcache

WordPress.org/plugins/memcached

— Redis

WordPress.org/plugins/wp-redis

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wp-content/object-cache.php

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W3 Total Cache +

Batcache

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Using Transients and the Object Cache

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Transients vs

Object Caching

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Transients use object caching, if available

Otherwise, the options table

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The Object Cache API uses an object caching

backend, if available

Otherwise, in-process PHP memory

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Transient API set_transient( $key, $data, $ttl )

get_transient( $key )

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Object Cache API wp_cache_get( $key, $group )

wp_cache_set( $key, $data, $group, $ttl )

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Avoiding Cache Stampedes and

Cold Caches

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$item = get_transient('footer_item');if ( ! $item ) { // Some poor person has to WAIT $get = wp_remote_get( get_option( 'footer_url' ) ); if ( ! is_wp_error( $get ) ) { $item = wp_remote_retrieve_body( $get ); wp_set_transient( 'footer_item', $item, 300 ); } }echo $item;

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TLC Transients —

bit.ly/tlc-transients

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function fetch_footer_item() { $get = wp_remote_get( get_option( 'footer_url' ) ); if ( ! is_wp_error( $get ) ) { return wp_remote_retrieve_body( $get ); } else { return false; }}

echo tlc_transient('footer_item') ->update_with('fetch_footer_item') ->expires_in(300) ->background_only() ->get();

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Cache HTML Fragments

— bit.ly/fragment-cache

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$fragment = new CWS_Fragment_Cache( 'unique-key', 3600);

if ( ! $fragment->output() ) { // START functions_that_do_stuff_live(); these_should_echo(); // END $fragment->store();}

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In review

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Caching for speed —

Caching for scale

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Less work —

Generic output

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Cache the whole page

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Think Nginx and Varnish, not PHP caching solutions

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Check out my whacky new plugin

github.com/markjaquith/cache-buddy

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Use Object Caching

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Leverage Transients (or maybe the Object Cache directly)

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Stampedes are bad

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Cache expensive, reusable HTML

fragments

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Q A(if we have time, which we probably do not)

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