Tutorial

How To Install and Use Memcache on Ubuntu 12.04

Published on August 13, 2012

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Ubuntu 12.04

Status: Deprecated

This article covers a version of Ubuntu that is no longer supported. If you are currently operate a server running Ubuntu 12.04, we highly recommend upgrading or migrating to a supported version of Ubuntu:

Reason: Ubuntu 12.04 reached end of life (EOL) on April 28, 2017 and no longer receives security patches or updates. This guide is no longer maintained.

See Instead:
This guide might still be useful as a reference, but may not work on other Ubuntu releases. If available, we strongly recommend using a guide written for the version of Ubuntu you are using. You can use the search functionality at the top of the page to find a more recent version.

About Memcache

Memcache is a system that works to speed up virtual private servers by caching server information. The program allows you to allocate a specific amount of the server ram toward caching recently queried data for a certain amount of time. Once the data is requested again, memcache speeds up the process of retrieving it by displaying the cached information instead of generating the result from the database.

Setup

The steps in this tutorial require the user to have root privileges. You can see how to set that up in the Basic Users Tutorial. Before starting off, it’s a good idea to update apt-get to make sure that all of the packages we download to the VPS are up to date.

sudo apt-get update

Additionally, you should have MySQL and PHP installed on the virtual server.

sudo apt-get install mysql-server php5-mysql php5 php5-memcache

Install Memcache

Installing memcache takes several steps.

To start, install memcached via apt-get.

sudo apt-get install memcached

The next step is to install php-pear, the repository that stores memcache.

sudo apt-get install php-pear

If you do not have a compiler on your server, you can download build-essential in order to install memcache:

sudo apt-get install build-essential

Finally use PECL (PHP Extension Community Library) to install memcache:

sudo pecl install memcache

Say yes by pressing enter during the installation when you are asked if you would like to “Enable memcache session handler support? [yes] :”

Once you have completed the installation of memcache with PECL on the VPS, add memcached to memcache.ini:

echo "extension=memcache.so" | sudo tee /etc/php5/conf.d/memcache.ini

Now you are ready to start using Memcache.

Confirm Memcache and See Stats

After Memcache is downloaded, you can check that it has been installed by searching for it:

ps aux | grep memcache

Additionally, you can see the memcache stats by typing:

echo "stats settings" | nc localhost 11211

Step Three—How Memcache Works

Memcache works by redirecting code to first attempt to retrieve data from the cache before querying the server’s database. The cache populates by saving recently retrieved server data for a certain amount of time. By caching recently requested information, future queries do not have to go through the longer process of retrieving the information from a database and can, instead, access it through the cache.

The memcache page shows this abbreviated code on its homepage to summarize the memcache process:

function get_foo(foo_id)
    foo = memcached_get("foo:" . foo_id)
    return foo if defined foo

    foo = fetch_foo_from_database(foo_id)
    memcached_set("foo:" . foo_id, foo)
    return foo
end

A Simple Memcache Example

This section will set up a simple php script to use memcache for retrieving a single value originally found in a mysql table.

The following steps set up a mysql user who can access the appropriate database, create a table to query, and insert the one value that we will test in the new mysql table.

Log into mysql: mysql -u root -p and execute the following commands:

use test;

grant all on test.* to test@localhost identified by 'testing123';

create table example (id int, name varchar(30));

insert into example values (1, "new_data");

exit;

Once you have exited MySQL, create the memcache script file:

nano memtest.php

We are now going to build up the php script step by step (the entire script will be at the end of the section):

Start off by creating a new persistent connection with memcache, which runs on memcache’s default port, 11211.
```
<?php
$meminstance = new Memcache();
$meminstance->pconnect('localhost', 11211);
```

The next step is to connect to the new mysql database with the user that we created earlier:

mysql_connect("localhost", "test", "testing123") or die(mysql_error());
mysql_select_db("test") or die(mysql_error());

After that, go ahead and create the query that we will pose to the server, as well as provide a key to identify that specific action:
```
$query = "select id from example where name = 'new_data'";
$querykey = "KEY" . md5($query);
```
The script first searches the cache for the answer to the query. If the result does not exist, the script reroutes the question to the original database. Once the query has been answered by the original database, the script stores the result in memcache, using the “set” command-- which both saves it and allows the user to designate the number of seconds that it should remain in the cache (600 would save it in the cache for 10 minutes).

When we run the script for the first time, it will inform us that the data was collected from the mysql database. However, as it does so, it stores the information in the cache, so that a second run of the script retrieves it from the cache and lets the user know.

In 10 minutes the cache is emptied once more and running the script will make it access the database once again.
```
$result = $meminstance->get($querykey);

if (!$result) {
       $result = mysql_fetch_array(mysql_query("select id from example where name = 'new_data'")) or die('mysql error');
       $meminstance->set($querykey, $result, 0, 600);
print "got result from mysql\n";
return 0;
}

print "got result from memcached\n";
return 0;

?>
```

Altogether the script looks like this:

<?php
$meminstance = new Memcache();
$meminstance->pconnect('localhost', 11211);

mysql_connect("localhost", "test", "testing123") or die(mysql_error());
mysql_select_db("test") or die(mysql_error());

$query = "select id from example where name = 'new_data'";
$querykey = "KEY" . md5($query);

$result = $meminstance->get($querykey);

if (!$result) {
       $result = mysql_fetch_array(mysql_query("select id from example where name = 'new_data'")) or die('mysql error');
       $meminstance->set($querykey, $result, 0, 600);
print "got result from mysql\n";
return 0;
}

print "got result from memcached\n";
return 0;

?>

Running the script on the command line produces the following results:

# php memtest.php 
got result from mysql

# php memtest.php 
got result from memcached

# php memtest.php 
got result from memcached

Conclusion

This tutorial covers speeding up the retrieval of data from a database by connecting it to memcache. However, do keep in mind that memcache’s strengh originates from the fact that is a cache—it is not a datastore. When using memcache, do not expect it to replace a database. Because memcache only holds values for a set length of time for a given key, you may not always find the information you need cached, and in cases like these, having the original server database is imperative.

Nevertheless, memcache is a very useful program and can do a lot to increase the server efficiency.

If you have any other questions about Memcache, feel free to ask about specifics on our forum.

By Etel Sverdlov

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Etel Sverdlov

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itommyyang • November 1, 2012

i got this error message: “PHP Fatal error: Class ‘Memcache’ not found in /home/tommy/www/memtest.php on line 2”

i don’t think i missed anything…

itommyyang • November 1, 2012

sorry i missed the following step: “sudo apt-get install mysql-server php5-mysql php5 php5-memcache”

problem solved… :) thanks for this awesome tutorial…

Etel Sverdlov

DigitalOcean Employee

• November 1, 2012

Thanks! Glad it worked out =]

yashuarc • November 21, 2012

Thank You!

daysunny2008 • December 2, 2012

hi.how about php connection.is it cashed too.or just the query cahsed?

Moisey Uretsky

DigitalOcean Employee

• December 2, 2012

If you want to speed up PHP connections to MySQL you would need to turn on persistent connections. If persistent connections are enabled when a script finishes executing it doesn’t close the MySQL connection, this allows the next time that the script is called with the same credentials to use an already open connection. This improves script response times as the script no longer has the overhead of opening and then closing the MySQL connection.

Memcache will cache queries so that if a script calls the same query repeatedly after the first time it is called and goes through MySQL to pull the data it will be cached in memcache. Then the next hit to that script will get that information from memcache without needing to run the query, again significantly improving performance.

c0smicalninja • January 30, 2013

Does it automatically cache the queries?

Moisey Uretsky

DigitalOcean Employee

• January 30, 2013

This article lays out how to install and use memcache so if you follow the simple guide on how to run your queries using memcache then you will be caching them with memcache before the query hits the DB.

levwiifun • February 9, 2013

Hi Guys, This method worked for me - this was a really helpful tutorial. Thanks a lot =) Well, i had to Restart the PHP-FPM after the set-up; until then the page was showing “Page temporarily not available.”

sudo /etc/init.d/php5-fpm restart

Just thought of adding this info. Thanks again.

jamgold • February 13, 2013

Sorry, but

sudo echo “extension=memcache.so” > sudo /etc/php5/conf.d/memcache.ini

just creates a file sudo in the current directory. The command should read

sudo echo “extension=memcache.so” > /etc/php5/conf.d/memcache.ini

2432612431302470453769504e6862 • March 20, 2013

Thank you so much…It worked at the first try for me…

camson • March 24, 2013

Does mean that port 11211 needs to be opened?

flaviomunizjr • May 8, 2013

Memcache Object ( [connection] => Resource id #2 )

Code: $meminstance = new Memcache(); $meminstance->pconnect(‘localhost’, 11211); print_r($meminstance);

Help!

Kamal Nasser

DigitalOcean Employee

• May 8, 2013

@camson If you’re accessing it locally, you shouldn’t need to open up ports in the firewall.

@flaviomuniz I do not see anything wrong in that code, please explain.

pablo • June 30, 2013

I worked the steps of this tutorial shortly after deploying a new droplet and received the following error (after executing “sudo pecl install memcache” and subsequently pressing “Enter”): <pre>running: make sh: 1: make: not found ERROR: `make’ failed</pre> Turns out all I had to do was execute: <pre>sudo apt-get install -y make</pre> and then re-run <pre>sudo pecl install memcache</pre>

Otherwise, everything else was as smooth as a …

rajeev1204 • July 2, 2013

There is a mistake in one of the steps and has still not been corrected.

sudo echo “extension=memcache.so” > sudo /etc/php5/conf.d/memcache.ini A user above has already pointed out, this command just creates a file called sudo in the current directory. Please remove the sudo from the second part of the command.

Kamal Nasser

DigitalOcean Employee

• July 2, 2013

@rajeev1204: Updated the article. Thanks!

sysadmin190099 • July 17, 2013

Good tutorial. I needed memcache in order to activate caching for a prestashop installation. Thanks.

geet • July 24, 2013

Hello there! I have been getting optimizing crazy… and would like some advice. I followed the tutorial above and all worked (you guys are awesome with all your tutorials…)

The question, I am running WordPress and already setup Linux, nginx, MySQL, PHP (LEMP) stack on Ubuntu 12.04: https://www.digitalocean.com/community/articles/how-to-install-linux-nginx-mysql-php-lemp-stack-on-ubuntu-12-04

Was me doing the above installs foolish since Varnish was already doing most of the work? My admin feels slower after this tutorial.

Should I remove the below packages as they might be using more processor power? php-pear build-essential memcache memcached

Also from the top of the install “sudo apt-get install mysql-server php5-mysql php5 php5-memcache” I likely didnt need to run this but I did… Should I be removing “php5 and php5-memcache”

Sorry for all the questions, maybe some of this is over my head, but you guys make it so easy to work on my Droplet, I maybe went over board?=)

geet • July 24, 2013

I forgot to mention I had already installed Varnish with this tutorial: https://www.digitalocean.com/community/articles/how-to-install-wordpress-nginx-php-and-varnish-on-ubuntu-12-04

Kamal Nasser

DigitalOcean Employee

• July 25, 2013

@geet: Even though Varnish and Memcache both cache stuff, they’re two different things. Having both of them should not slow your site down. Did you modify any of your code to use memcached or did you just install it?

nhatkhoa • August 11, 2013

my server already running so i think mySQL and PHP already installed. Plz teach me how to check if it installed or not? I dont want to install it 2 times may mess-up my vps. thanks

Additionally, you should have MySQL and PHP installed on the virtual server.

sudo apt-get install mysql-server php5-mysql php5 php5-memcache

Kamal Nasser

DigitalOcean Employee

• August 11, 2013

@nhatkhoa: If you run the apt-get install command twice, it won’t install them twice so you’re okay. Run the whole command just in case.

kenthul • August 22, 2013

Thanks for a great tutorial.

If i run my application on 2x servers/droplets, should I open up 11211?

Also, should I use memcache on all pages that would be used alot? Like my search page and my product page that works like a template, product.php?id= someItem

$meminstance = new Memcache(); $meminstance->pconnect(‘localhost’, 11211); etc etc

kenthul • August 23, 2013

Also, is it a good idea to use memcache with APC installed?

Kamal Nasser

DigitalOcean Employee

• August 24, 2013

@ken.thul: I recommend having a shared memcached server so that both app servers can share the same data. Using it a lot won’t be a problem.

Memcache and APC are two different things. Memcache is a memory object cache while APC is opcode cache.

ng • September 4, 2013

I also had to install: sudo apt-get install php5-dev (ubuntu 13.04)

istikeer • September 23, 2013

I got this message at the end of the installation: “You should add “extension=memcache.so” to php.ini”

phillip • September 23, 2013

Alright, I’m not very experienced with this and I’d appreciate any help. I’m getting the following error-

Memcache::pconnect(): Server localhost (tcp 11211) failed with: Connection refused (111) in /memcache/memcache.php on line 3 PHP Warning: Memcache::pconnect(): Can’t connect to localhost:11211, Connection refused (111) in /memcache/memcache.php on line 3 PHP Warning: Memcache::get(): No servers added to memcache connection in /memcache/memcache.php on line 11 PHP Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in /memcache/memcache.php on line 14

I’ve got a remote mysql server running so I’m not sure if that is causing the problems…

Kamal Nasser

DigitalOcean Employee

• September 24, 2013

@phillip: Is Memcached running? What’s the output of <pre>sudo netstat -plutn | grep 11211</pre>?

tusharthakur123 • September 26, 2013

How to disable or remove this memcache function? This causing issue to my Prosper202 tracking software.

Kamal Nasser

DigitalOcean Employee

• September 27, 2013

@tusharthakur123: Delete <code>/etc/php5/conf.d/memcache.ini</code>:

<pre>rm /etc/php5/conf.d/memcache.ini</pre>

tj • September 28, 2013

I had to change

$meminstance->pconnect(‘localhost’, 11211); to $meminstance->connect(‘localhost’, 11211);

nimopress • October 9, 2013

hi,

I have LEMP and wordpress installed. I am assuming this enables me to install and use memcache to my wordpress database? In the section below, do i replace ‘test’ with my wordpress db, user & password details?

use test;

grant all on test.* to test@localhost identified by ‘testing123’;

create table example (id int, name varchar(30));

insert into example values (1, “new_data”);

exit;

Kamal Nasser

DigitalOcean Employee

• October 9, 2013

@nicholas.ongpl: MySQL and Memcache are not the same. You can’t replace MySQL with memcache on Wordpress (or anything really).

Take a look at <a href=“http://wordpress.org/plugins/wp-ffpc/”>http://wordpress.org/plugins/wp-ffpc/</a>

nimopress • October 10, 2013

Sorry Kamal, maybe I could have been clearer. I know MySQL and Memcache are 2 different things. What I mean was ‘A Simple Memcache Example’…