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Memcached

# Memcached Server Configuration for MediaWiki

This article details configuring and utilizing Memcached to improve the performance of your MediaWiki installation. Memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load. For a busy MediaWiki site, Memcached can dramatically reduce response times and improve overall scalability.

What is Memcached?

Memcached operates by storing frequently accessed data in RAM, allowing for quicker retrieval than repeatedly querying the database. It's particularly effective for caching data that's expensive to generate, such as the results of complex database queries used for page rendering. MediaWiki, by default, relies heavily on database queries. Caching frequently accessed parts of pages significantly reduces the load on the database server, leading to faster page loads for users. While PHP is commonly used with Memcached, other languages can also interface with it.

Installation

The installation process varies depending on your operating system. Here's a general overview. These instructions assume you have root or administrator privileges.

Linux (Debian/Ubuntu)

Open a terminal and execute the following commands:

```bash sudo apt update sudo apt install memcached php-memcached ```

Linux (CentOS/RHEL)

Open a terminal and execute the following commands:

```bash sudo yum install memcached php-pecl-memcached ```

Windows

Installation on Windows typically involves downloading a pre-compiled binary of Memcached and a PHP extension (usually a DLL file). Refer to the official Memcached documentation for detailed instructions: [http://memcached.org/](http://memcached.org/). You will also need to configure your `php.ini` file to load the `php_memcached.dll` extension.

Configuration

After installation, you need to configure both Memcached itself and MediaWiki to utilize it.

Memcached Configuration

The Memcached configuration file is typically located at `/etc/memcached.conf` (Linux) or in the Memcached installation directory (Windows). Here are some key settings:

Parameter Description Default Value
`-m` Maximum amount of memory to use in MB. 64
`-p` Port to listen on. 11211
`-l` Interface address to listen on. 127.0.0.1
`-u` User to run as. root
`-t` Number of threads. 4

Adjust these values based on your server's resources and expected load. Increasing the memory allocation (`-m`) is usually the most effective way to improve performance.

MediaWiki Configuration

Edit your `LocalSettings.php` file. Add the following lines:

```php $wgMemCachedLocalServers = array( '127.0.0.1:11211' // Replace with your Memcached server address and port );

$wgCacheDirector = true; ```

`$wgMemCachedLocalServers` defines the Memcached servers that MediaWiki will use. You can specify multiple servers for redundancy and scalability. `$wgCacheDirector = true;` enables the caching director, which manages the caching process.

Advanced Configuration and Monitoring

For larger deployments, consider these advanced configurations:

Multiple Memcached Servers

For increased redundancy and capacity, you can configure MediaWiki to use multiple Memcached servers. Simply add more entries to the `$wgMemCachedLocalServers` array in `LocalSettings.php`.

```php $wgMemCachedLocalServers = array( '127.0.0.1:11211', '192.168.1.10:11211', '192.168.1.11:11211' ); ```

Statistics and Monitoring

Memcached provides a simple text-based interface for monitoring its performance. You can use the `telnet` command to connect to the Memcached server and retrieve statistics.

```bash telnet 127.0.0.1 11211 ```

Once connected, type `stats` and press Enter to view detailed statistics. Tools like Nagios, Zabbix, or Memcached monitoring web interfaces can provide more comprehensive monitoring.

Caching Levels

MediaWiki uses different caching levels. Memcached primarily impacts the following:

⚠️ *Note: All benchmark scores are approximate and may vary based on configuration. Server availability subject to stock.* ⚠️

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