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Un-Scaling WordPress WordCamp DC 2017 Mike Schroder Director of WordPress Strategy @ DreamHost @GetSource - https://getsource.net

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What does it mean to scale?

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Vertical scaling: More RAM and CPU.

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Horizontal scaling: More servers with the RAM and CPU.

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Vertical scaling

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Vertical scaling

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Horizontal scaling

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Horizontal scaling

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What does it mean to un-scale?

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No content

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Simplified architecture.

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Let’s see what we can do with shared and a 512mb VPS.

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How much RAM does WordPress need?

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Page View => ~3-120mb Image Operations => ~256mb+

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Does WordPress scale?

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Adjacent technologies help WordPress serve higher traffic sites well.

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We’re really talking about caching.

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If you’ve hit PHP, you’ve lost.

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But it’s not as bad as it used to be.

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Opcode cache.

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Usually OPcache, included with PHP 5.5+

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Higher percentage of improvement on hosts with low CPU resources.

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Test: ~100 users during 1 minute.

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Shared PHP 5.6 100/min Average: 1045ms

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Shared PHP 5.6 w/OPcache 100/min Average: 782ms

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Shared PHP 7 100/min Average: 760ms

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Shared PHP 7 w/OPcache 100/min Average: 507ms

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Persistent object caching.

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By default, WP’s internal cache expires with each request.

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Persistent object caching helps dynamic sites most.

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Usually this is Memcached or Redis.

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Front end caching.

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Save the final output of PHP.

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Disk, Varnish, Nginx.

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Front end caching helps static sites most.

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Shared PHP 7 w/OPcache + WP Super Cache PHP Routed: 100/min Average: 69ms

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Like with “firewall” plugins, treat PHP-based solutions with skepticism.

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Shared PHP 7 w/OPcache + WP Super Cache Disk Backed: 100/min Average: 32ms

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Shared PHP 7 w/OPcache + WP Super Cache Disk Backed: 1000/min Average: 43ms

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Shared PHP 7 w/OPcache + WP Super Cache Disk Backed: 5000/min Average: 2158ms

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Let’s take a look at our VPS.

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VPS PHP 7 w/OPcache 100/min Average: 169ms

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VPS PHP 7 w/OPcache + Varnish RAM Backed 100/min Average: 21ms

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VPS PHP 7 w/OPcache + Varnish RAM Backed 5000/min Average: 17ms

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5000/min => 216,000,000/month

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How much RAM do adjacent services need?

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Basically anything helps for OPcache. So have some.

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32-96mb for Memcached, with slab size > than options. (4mb is a good start)

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128mb Varnish Have some VCL.
 https://github.com/tollmanz/varnish-vcl-collection

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Thanks! Mike Schroder @GetSource https://getsource.net Director of WordPress Strategy @ DreamHost