How to reduce server load and improve WordPress speed with Memcached

[Viktor Vogel]

In my last article about Varnish in a Docker container, I’ve explained how to easily activate server-side caching and what advantages you can get with this mechanism. Today, I will show you how you can reduce server load and drastically improve your WordPress website speed with Memcached.

Memcached – a distributed memory caching system


Memcached caches data and objects directly into the memory (RAM) and reduces the amount of times an external source has to be read (e.g. the database or API-calls). This especially helps dynamic systems like WordPress or Joomla! by noticeably improving the processing time!

Installing Memcached


On my server, I run Plesk Onyx with CentOS 7.x. This tutorial also applies to other systems, just remember to use the system-specific commands (e.g. apt-get instead of yum). To install Memcached, first access your server via SSH and use the command line:

yum install memcached

After the installation process, we start it with:

service memcached start

Next we have to install PECL Memcached for the corresponding PHP version. WordPress is fully compatible with PHP 7, so let’s activate Memcached for the latest PHP 7.1 version. Start by installing all the necessary packages to add our custom PHP module in Plesk.

yum install make plesk-php71-devel gcc glibc-devel libmemcached-devel zlib-devel

Build the module with these instructions. You don’t have to specify the libmemcached directory manually, simply hit Enter if prompted.

/opt/plesk/php/7.1/bin/pecl install memcached

In the next step, we have to add a line to the corresponding configuration file to register the module in PHP. You can use the command line without having to open the ini file with an editor.

echo "extension=memcached.so" > /opt/plesk/php/7.1/etc/php.d/memcached.ini

And finally, re-read the PHP handlers so that you see the module in the PHP overview in the Plesk GUI.

plesk bin php_handler --reread

You can check the phpinfo()-page now to find out if the memcached module was loaded properly.


Memcached – phpinfo() output


Or directly via the command line:

/opt/plesk/php/7.1/bin/php -i | grep "memcached support"


Memcached – PHP command line check

Activate Memcached in WordPress


Once Memcached is installed on the server, it is easy to activate it in WordPress. First, we need to activate the Memcached backend with a special script that auto-detects whether to use Memcached as the caching mechanism.

Download the script from https://github.com/bonny/memcachy and move all files to the /wp-content/ folder.

If you didn’t change the default port (11211) of Memcached, then you are ready to use it directly. If you’ve changed it, then you will have to add the following code to the wp-config.php (placed in the root of your WordPress instance).

$memcached_servers = array( array( '127.0.0.1', 11211 ) );

Okay, once the backend is activated, we will install a cache plugin to store and serve rendered pages via Memcached. Install the plugin Batcache (https://wordpress.org/plugins/batcache/) using the installation instruction.

1. Download and unzip the package
2. Upload the files advanced-cache.php to the /wp-content/ folder
3. Open wp-config.php and add the following line
   1. 
      define('WP_CACHE', true);
   2. Important: Be sure that Memcached is enabled properly for the selected PHP version before adding this line else an error will be thrown!
4. Upload the file batcache.php to the /wp-content/plugins/ folder

That’s pretty much it! You can open the advanced-cache.php file and adjust the settings for your needs. The file batcache.php is a small plugin that regenerates the cache on posts and pages. Don’t forget to activate the plugin in the backend on the plugin page!

Verify that Memcached works properly in WordPress


Now, let’s verify that you did everything correctly. The easiest way to see whether the rendered page was sent from cache is to add an additional header field to the response.

To achieve it, you have to modify the advanced-cache.php file. Open the file and search for

var $headers = array();

Change this line to

var $headers = array('memcached' => 'activated');

Open the Developer Tools in your browser, select the Network tab and reload your website several times (just to be sure the page is loaded from the cache) and check the response headers. If you see the memcached header field, then everything is fine!


Memcached – Response Headers Check

Let’s do some stress tests with Blitz.io!


We can test the load performance by stress testing, which will load the website with many concurrent users per second for a certain time span. Without any security and overload protection, your server should start to respond slower until the requests cannot be handled anymore. With Memcached activated, your server should be able to serve intensive requests longer without throwing errors.

Let’s run some load and performance tests with Blitz.io.

Note: For this stress test I took the same small server that I used for the tests with Varnish (only 1 CPU and 500MB Memory)!

Result WITHOUT Memcached:


Stress test – WordPress without Memcached


It is the same result like in the Varnish stress test. As you can see, I had to abort the stress test because the server couldn’t handle the requests less than 5 seconds and less than 50 concurrent users into the test. After just 15 seconds, the server collapsed completely and no requests could be managed anymore!

Result WITH Memcached:


Stress test – WordPress with Memcached


As you can see, the Memcached cache allows us to keep the server stable even under heavy load. The small test server handled over 400 concurrent users and responded all requests over 50 seconds without any errors. After 50 seconds and almost 450 concurrent users, the server finally overloaded and stopped accepting further requests. With a more powerful server, the numbers would be much higher.

Therefore, it’s a great idea to use Memcached to keep your website reactive, even when it suffers a simple attack. For real DDoS attacks (Distributed Denial of Service attack) you’d be better off with CloudFlare ServerShield to protect your server.

Summary: WordPress with Memcached works perfectly


Memcached can greatly improve the performance of your WordPress website and reduce the CPU-load of your server. It’s easy to set up a working environment and it works out-of-the-box.

Thank you for reading my article, let me know your comments!

Have fun improving the speed of your WordPress website and stay Plesky!

The post How to reduce server load and improve WordPress speed with Memcached appeared first on Plesk.

Continue reading...

 

[IgorG]

For security reasons, I would strongly recommend adding line

OPTIONS="-l 127.0.0.1"

at the end of file /etc/sysconfig/memcached and restart memcached service. It will bind port 11211 only to localhost.

Also following commands would useful for memcached monitoring and stats:

# echo "stats settings" | nc localhost 11211
# /usr/bin/memcached-tool localhost:11211

 

[Laurence@]

Surely this is completely insecure on shared hosting due to the real possibility of cache poisoning? Memcached would need to ran per domain under a user ID and different unix socket?

 

[Laurence@]

I was hoping with the Docker integration we would now be able to offer secure Memcached hosting to users but with Docker restricted to admin users each customer that wants an advanced set up with Memcached (and Varnish) would have to be setup manually. Any plans for end user Docker permissions?

 

[Viktor Vogel]

Hello Laurence,

my tutorial was just an example how to activate Memcached on a Plesk Server in general. Memcached does not have built-in security measures for shared hosting as far as I know, so this should only be used on a dedicated server. This is a good point, I will update my article in the blog.

I cannot answer you the Docker restriction question. Maybe @IgorG knows more?

Cheers

 

[sandeep]

Hello I am trying to install memcache for wordpress and trying this command on plesk onyx17 latest version on ubuntu16 with latest version :
apt-get install make plesk-php71-devel gcc glibc-devel libmemcached-devel zlib-devel
but its giving this error :

root@www ~ # apt-get install make plesk-php71-devel gcc glibc-devel libmemcached-devel zlib-devel
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package plesk-php71-devel
E: Unable to locate package glibc-devel
E: Unable to locate package libmemcached-devel
E: Unable to locate package zlib-devel

How can i install the memecache, which is correct commands

 

[IgorG]

@sandeep you should use Ubuntu names of packages instead of CentOS. It will be something like plesk-php71-dev, glibc-dev libmemcached-dev zlib-dev

 

[sandeep]

i tried this with
root@www ~ # apt-get install make plesk-php71-dev gcc libmemcached-dev git pkg-config zlib1g-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package plesk-php71-dev

but still not able to do

 

[sandeep]

root@www ~ # apt-get install make plesk-php71-dev gcc glibc-dev libmemcached-dev zlib-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package plesk-php71-dev
E: Unable to locate package glibc-dev
E: Unable to locate package zlib-dev

 

[IgorG]

Try to install this package with dpkg plesk-php71-dev_7.1.7-ubuntu16.04.17070710_amd6..>

 

[sandeep]

i am unable to understand , can you please tell me full command thanks

 

[IgorG]

i am unable to understand , can you please tell me full command thanks

# wget http://autoinstall.plesk.com/PHP_7....hp71-dev_7.1.7-ubuntu16.04.17070710_amd64.deb
# dpkg -i plesk-php71-dev_7.1.7-ubuntu16.04.17070710_amd64.deb

 

[sandeep]

dpkg -i plesk-php71-dev_7.1.7-ubuntu16.04.17070710_amd64.deb

(Reading database ... 154077 files and directories currently installed.)
Preparing to unpack plesk-php71-dev_7.1.7-ubuntu16.04.17070710_amd64.deb ...
Unpacking plesk-php71-dev (7.1.7-ubuntu16.04.17070710) over (7.1.7-ubuntu16.04.17070710) ...
dpkg: dependency problems prevent configuration of plesk-php71-dev:
plesk-php71-dev depends on plesk-php71 (= 7.1.7-ubuntu16.04.17070710); however:
Package plesk-php71 is not installed.

dpkg: error processing package plesk-php71-dev (--install):
dependency problems - leaving unconfigured
Errors were encountered while processing:
plesk-php71-dev

 

[IgorG]

Package plesk-php71 is not installed.

Just install PHP7.1 through Plesk Installer, for example.

 

[UFHH01]

Hi sandeep,

pls. see as well possible examples for "HOW TO ADD ADDITIONAL PLESK - RELATED sources.lists" at => #9

 

[st3ve87]

For some reason I don't see any "memcached activated" in the headers after adding var $headers = array('memcached' => 'activated'); to the advanced-cache.php file. In SSH I do see memcached support => enabled. Only the WordPress part Im failing at. What can I do to verify memcached is working properly?

Btw, I also use cloudflare. Can that cause that my headers won't show memcached?

 

[CoyoteKG]

Hello, I followed instructions, and finished without any problems.
But when I check WP site, in response header there is no info that memcached is active, even I set advanced-cache.php like you said.



Also, when I activated batcache, my PageSpeed Evaluation droped from 90/100 to 80/100.

Before that I used Autoptimize plugin. with these Additional nginx directives.

gzip on;
gzip_vary on;
gzip_proxied any;
gzip_comp_level 6;
gzip_buffers 16 8k;
gzip_http_version 1.1;
gzip_types image/svg+xml text/plain text/html text/xml text/css text/javascript application/xml application/xhtml+xml application/rss+xml application/javascript application/x-javascript application/x-font-ttf application/vnd.ms-fontobject font/opentype font/ttf font/eot font/otf application/font-ttf;
location ~* \.(jpg|jpeg|png|gif|ico|css|js|txt)$ {
    expires 7d;
}

Also, I check batcache instructions, and they mentioned

Test by reloading a page in your browser several times and then viewing the source. Just above the </head> closing tag you should see some Batcache stats.

and there is no any Batcache stats.
What I missed? Autoptimize plugin is deactivated

Also, there is a warning

This plugin hasn’t been tested with the latest 3 major releases of WordPress. It may no longer be maintained or supported and may have compatibility issues when used with more recent versions of WordPress.