Varnish Cache and its usage in the real world

Ivan ChepurnyiOwner

EcomDev BV

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About me

• Technical Consultant, Owner at EcomDev B.V.

• Started as one of the first five developers in original Magento core team

• Magento Developer Coach in Europe

• Main areas of my expertise:– System Architecture – Performance Optimization– Test Driven Development– Complex Customizations

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Varnish

is not a cache backend

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Varnish

is a frontend caching proxy

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Simple Workflow

First call to a page

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Simple Workflow

Subsequent requests

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How Varnish Works

recv

hit pass miss

hash pipe

deliver

fetch

• recv – request is received from client

• pipe – direct output of backend data (streaming)

• hash – request is cacheable, lookup cache entry

• pass – request is not cacheable

• hit – cache entry is found

• miss – cache entry not found

• fetch – retrieval of data from backend

• deliver – return data to client

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What can we do with it?

• Cache static pages (Homepage, CMS, Contacts, etc)

• Cache catalog pages:– Category listings– Product search results– Product view pages

• Cache page parts:– CMS Blocks– Header– Footer

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Is it possible to clear Varnish cache based on product, category,

store, etc?

YES!!!

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The Secret is in

Cache Object structure

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Cached Object in Varnish

Cached Object

Response Headers

Response Body

Cache Metadata

Cache Content

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We just going to supply object ID with its type in response headers, so it later

on can be used to flush pages containing our object.

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But is it possible to make cache lifetime dynamic per product, category, etc?

YES!!!

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You can supply a response header, that contains a TTL of the page.

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So what should be done to implement Varnish in Magento with all the

benefits?

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Varnish in Magento

• Collect current page objects, that are shown on the page. Also add them into response headers.

• Create a connector to a Varnish admin protocol, that will be used for flushing of the page by object ids.

• Implement auto-updated AJAX blocks for:– Shopping cart– Wishlist– Customer Account links

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But I have good news:

I alredy developed a module that gives you a solid foundation for using Varnish in your

project!

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EcomDev_Varnish

Download URL: http://bit.ly/ecomdev_varnish

Requires:• Varnish 3.0• Minimal changes to your theme

Supports:• Flush of cache on update of product, category, cms page, csm

block, price rules• Client side cacheable AJAX placeholders (Cart, Wishlist, etc)• Possibility to make a cache based on customer segment • Cache for logged in users

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Before you start using it…

• Make a list of dynamic blocks in your project:– Shopping Cart– Login blocks– Special Promo for Customer

• Validate possible visitor segments of your project:– Customer group– Language / Country

• Make a list of themes you need to modify

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Making an element dynamic on varnish cached page

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Code Sample Dynamic Block

<default_varnish>

<reference name=”parentBlock”>

<action method="unsetChild”>

<block>dynamicBlockAlias</block>

</action>

<block

as="dynamicBlockAlias”

name=”dynamicBlockPlaceholder"

template="ecomdev/varnish/wrapper/placeholder.phtml"

type="core/template">

<action method="append">

<block>dynamicBlock</block>

</action>

<action method="setBlockName">

<block>dynamicBlock</block>

</action>

<action method="setCookie">

<cookie>dynamicCookie</cookie>

</action>

<action method="setWrapperId">

<htmlId>elementId</htmlId>

</action>

</block>

</reference>

</default_varnish>

Layout File • parentBlock – name of the parent block

• dynamicBlockAlias – alias of the dynamic block in parent block

• dynamicBlockPlaceholder – unique name of your placeholder

• dynamicBlock – name of the original dynamic block

• dynamicCookie – name of the cookie for dynamic blocks

• elementId – HTML ID for the placeholder div, that is going to be used as container

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Available Dynamic Cookies

• quote_checksum – checksum of the current quote contents

• customer_checksum – checksum based on the customer identification, if logged in customer gets changed

• is_logged_in – boolean flag of the logged in state of the visitor

• segment_checksum – checksum of the current customer segment: – customer group id– store view

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How does it work?

• Your original block gets wrapped by a custom div with some JS code

• When customer visits a page, JS checks for a cookie value and compares it with latest saved one in local/session storage

• If it is different it requests /varnish/ajax/reload for retrieving dynamic content and saves it to local/session storage

• If it is the same, it just updates block from local/session storage

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Adding custom TTL for a page

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Code Sample Custom TTL

// Somewhere in your code you just simply call it

// Varnish module will take the lowest value in array of TTL that were added

Mage::helper(‘ecomdev_varnish’)

->addTtl($timeInSeconds);

Code Block

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Making custom page cacheable

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Code Sample Custom Page

<config> <varnish> <pages> <layout_handle_name translate="label" module=”your_module"> <label>Your Page Name</label> </layout_handle_name> </pages> </varnish>

<default> <varnish> <pages>

<layout_handle_name_time>360</layout_handle_name_time>

</pages> </varnish> </default></config>

config.xml• layout_handle_name – full

name of the layout handle that should be cacheable

• your_module – name of the module used for translation of label

• Your Page Name – name of your pages, that will be shown in System Configuration - Varnish Cache

• 360 – default cache lifetime of the page

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Varnish vs Full Page Cache

Varnish

• Avg. time to first byte 30ms

• Dedicated software

• Tools to monitor cache usage

• Scalable

• Requires adaptation of themes for dynamic parts

• Possibility to flush group of pages

Magento FPC implementation

• Avg. time to first byte 300-400ms

• Magento code level

• N/A

• Only as another backend node

• Most of the time it is not required

• N/A

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But why do I need to use EcomDev_Varnish?

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EcomDev_Varnish vs the others

• Cache lifetime specified on Magento code level, without changing VCL

• By using collectors & processors, it can be easily extended to support additional entities

• Client-side cacheable dynamic parts

• Cache enabled for all kind of visitors

• Saves your money on hardware

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The choice is up to you!

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OpenSource Roadmap 2014

1. Finalize EcomDev_Varnish module and make it open source;

2. EcomDev_PHPUnit refactoring for API based fixtures;Progress: 20%

3. Working on EcomDev_Index module, to provide alternative of standard indexation mechanism in Magento:– Flat Indexers (failover indexation)– UrlRewrites (full refactor of existing module)– Layered Navigation (Sphinx)– Better Search (Sphinx)

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Thank You!

Questions?

Email: ivan@ecomdev.org

Website: http://www.ecomdev.org

LinkedIn: http://nl.linkedin.com/in/ivanchepurnyi

Twitter: https://twitter.com/IvanChepurnyi