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Varnish Cache is a web application accelerator, also known as a caching HTTP reverse proxy, which is designed for content-heavy dynamic web sites. And today, we have tried Varnish on a Magento default sample shop, to see how well Varnish helps on the loading speed, compared to the bare Magento install.

1          Varnish Features for Magento

1.1         Enable full page caching using Varnish.

For a sample Magento website, Varnish is enabled to cache most of the pages, like Home Page, and other Page Categories.

1.2         Varnish servers are configurable in Admin, under System / Configuration / General – Varnish Options

You can specify which Varnish server Magento website is using. If just use one server for hosting Magento website, we can install varnish on the same server and input the blank as 127.0.0.1:80 which is by default.

1.3         Automatically clears (only) cached pages when products, categories and CMS pages are saved.

For example, if you add a new product or update the parameters of the products, when you click the save button in the admin page, the website data which stored in Varnish will be automatically purged, so that you won’t read the old data in the Varnish Cache.

In the figure below, I modified the price of HTC Touch Diamond, when I click ‘Save’, the Data in the Varnish Cache is purged, so you can see the price of the product is up-to-date.

1.4         Adds a new cache type in Magento Admin, under System / Cache Management and offers the possibility to deactivate the cache and refresh the cache.

For example, if you finish adding a new category, you click ‘Save Category’, then you click on the Home Page, you won’t see the new category in the navigation bar, you need to manually refresh the Vanish cache in Magento Admin under System / Cache Management. You can see the picture below :

1.5         Notifies Admin users when a category navigation is saved and Varnish cache needs to be refreshed so that the menu will be updated for all pages.

You can see the green lines under the navigation bar.

1.6         Turns off varnish cache automatically for users that have products in the cart or are logged in, etc.)

Products in the cart and user logged in which are user-specific parts, which needs to interact with Apache directly, which can be passed from Varnish cache.

2          Varnish Installation

2.1         Prerequisites

it’s better running on a 64bit Linux.

wget http://download.fedora.redhat.com/pub/epel/5/x86_64/jemalloc-2.1.3-2.el5.x86_64.rpm
rpm -ivh jemalloc-2.1.3-2.el5.x86_64.rpm

Hardware Configuration for Magento + Varnish Server

• Xen Server
• CPU: Quad-Core Xeon  E5506  @ 2.13GHz
• Memory: 4G

2.2         Install Varnish 2.1.5

wget http://repo.varnish-cache.org/source/varnish-2.1.5.tar.gz
tar zxf varnish-2.1.5.tar.gz
cd varnish-2.1.5
./configure
make && make install

2.3         Install Varnish Module

• Download the latest version of Magento and install it
• cd [magento root folder]
• Create folder app/code/local/Varnish
• Copy folders controllers/  etc/  Helpers/  Model/  under  app/code/local/Varnish/
• Copy Magneto_Varnish.xml to app/etc/modules/
• Copy varnish.vcl to /etc/varnish/

2.4         Install Modman

curl http://module-manager.googlecode.com/files/modman-1.1.5 > modman
chmod +x modman
mv modman /usr/bin

2.5         Install git

rpm  –ivh  http://download.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
yum install git

2.6         Clone the git repository

cd [magento root folder]
modman init
env GIT_SSL_NO_VERIFY=true modman magneto-varnish clone https://github.com/madalinoprea/magneto-varnish.git

2.7         Apache Config

vim /etc/httpd/conf/httpd.conf
change Listen 80 to Listen 8080

2.8         Launch Varnish

We will use 1G for the cache storage. It depends on how much objects need to be cache, 1G is sufficient in most of the cases.

/usr/local/sbin/varnishd  -f /etc/varnish/varnish.vcl -s malloc,1G -T 127.0.0.1:2000

Now Varnish is ready for Magento.

3          Varnish tests for Magento (Magento Version 1.5.1)

3.1         Bench report for bare Magento and Magento + Varnish (Load testing tool : Funkload)

For the sample Home page of Magento, Figure 1 is without Varnish and Figure 2 is with Varnish. You can make the comparison.

In Figure 1, I made the load testing with concurrent users 2, 6, 10, 14, 18, 22. You can easily read from the table below the chart, The first column CUs means concurrent users, the third column Rating which is based on the response time of Home page of Magneto. You can find the response time for 14 CUs are becoming Good, and 18 CUs are becoming FAIR, 22 CUs are becoming POOR, which indicates that if the concurrent users are larger than 22, the performance of bare Magento will be POOR or UNACCPETABLE.

In Figure 2, I made the load testing with concurrent users 20, 40, 60, 80, 100, 120. The below test is also based on the sample home page of Magento. You can see even with Maximum 120 concurrent users, The Rating is still Excellent.

4          Testing Scenarios (Load testing tool: Jmeter)

The test scenarios below are tested under three platforms. The .cvs files are exported from the test results of Jmeters :

• Magento
• Magento + Varnish
• Magento + Varnish + J2T_AJAXCART_LITE-1.1.3

Clarification of the following figures :

• Column 1 : test pages sequence.
• Column 2 : how many times the pages are being loaded.
• Column 3 : the average time for loading the page.

4.1         Scenario 1 : Navigation

• Home Page : http://192.168.0.38/magento3/
• Page category A : http://192.168.0.38/magento3/furniture.html
• Page category A_a : http://192.168.0.38/magento3/furniture/living-room.html
• Product Page A_a_1 : http://192.168.0.38/magento3/furniture/living-room/ottoman.html
• Page category B_b : http://192.168.0.38/magento3/electronics/cell-phones.html
• Product Page C_c_2 : http://192.168.0.38/magento3/apparel/shoes/mens.html

4.2         Scenario 2 : Add to cart

• Home Page : http://192.168.0.38/magento3/
• Page category A : http://192.168.0.38/magento3/furniture.html
• Page category A_a : http://192.168.0.38/magento3/furniture/living-room.html
• Product Page A_a_1 + action add to cart : http://192.168.0.38/magento3/furniture/living-room/ottoman.html
• Shopping cart page : http://192.168.0.38/magento/checkout/cart/

4.3         Scenario 3 : Customer / Checkout

• Home Page : http://192.168.0.38/magento/
• Login Page : http://192.168.0.38/magento/customer/account/login/
• Create account page :
  • http://192.168.0.38/magento/customer/account/create/
  • http://192.168.0.38/magento/customer/account/createpost/
• Add default adresse page :
  • http://192.168.0.38/magento/customer/address/
  • http://192.168.0.38/magento/customer/address/formPost/
• Product Page A_a_1 + action add to cart :
  • http://192.168.0.38/magento/furniture/living-room.html
  • http://192.168.0.38/magento/furniture/living-room/ottoman.html
• Shopping cart page : http://192.168.0.38/magento/checkout/onepage/saveOrder/
• Checkout steps :
  • http://192.168.0.38/magento/checkout/cart/
  • http://192.168.0.38/magento/checkout/onepage/
  • http://192.168.0.38/magento/checkout/onepage/saveBilling/
  • http://192.168.0.38/magento/checkout/onepage/getAdditional/
  • http://192.168.0.38/magento/checkout/onepage/progress/
  • http://192.168.0.38/magento/checkout/onepage/saveShippingMethod/
  • http://192.168.0.38/magento/checkout/onepage/progress/
  • http://192.168.0.38/magento/checkout/onepage/savePayment/
  • http://192.168.0.38/magento/checkout/onepage/progress/
• Checkout success : http://192.168.0.38/magento/checkout/onepage/success/

4.4         Conclusion

According to the above tests, for the static pages, Varnish performs great. For the customer specific settings, like login, logout, the cart, and https pages, Varnish will not cache these data, which will need to be directly processed by Apache, so the load average time of the customer specific pages can’t be seen any difference with or without Varnish. Varnish is a good tool for basic web page navigation.