Why is Apache Optimization Important?

Apache is one of the cornerstones of web servers and directly affects the performance of websites hosted on Plesk. A poorly configured Apache server can lead to slow loading times, high server load, and even site crashes. Optimization allows the server to use its resources more efficiently, allowing it to handle more traffic smoothly. This improves user experience, increases SEO ranking, and boosts overall business performance.

Key Points:

Fast Loading Times: Users prefer fast-loading websites.
Low Server Load: Optimization ensures that the server consumes fewer resources.
Increased Traffic Capacity: An optimized server can handle more concurrent requests.
Improved SEO: Search engines rank fast and user-friendly websites higher.

Which Areas Should I Focus On in Apache Optimization?

Apache optimization covers a wide area. You can start by focusing on the following areas:

MPM (Multi-Processing Module) Selection: Apache's MPM determines how it handles requests. Different MPMs are available, such as Event, Worker, and Prefork. Choosing the right MPM significantly affects server performance.
KeepAlive Settings: KeepAlive keeps the connection between the client and the server open, allowing multiple requests to be sent over the same connection. When configured correctly, it reduces connection establishment costs and improves performance.
Module Optimization: Disabling unused or unnecessary modules reduces the server's resource consumption.
Caching: Caching static content reduces the server's load and shortens loading times.
Compression: By using compression algorithms such as Gzip or Brotli, you can reduce the size of web pages and reduce bandwidth usage.
Security Settings: Security vulnerabilities can negatively affect server performance. Configuring security settings correctly improves both performance and security.

How to Choose an MPM (Multi-Processing Module)? Which MPM is Right for Me?

MPM (Multi-Processing Module) is a module that determines how Apache handles requests. There are three main MPMs: Prefork, Worker, and Event. Each has different advantages and disadvantages. The choice depends on the server's hardware, operating system, and expected traffic.

Prefork: Creates a new process for each connection. Consumes more resources but is more compatible with older applications. Often used with PHP's mod_php mode.
Worker: Each process uses multiple threads. Consumes fewer resources and can handle more concurrent connections.
Event: Similar to Worker, but handles KeepAlive connections more efficiently. Ideal for high-traffic websites.

MPM	Advantages	Disadvantages	Suitable Scenarios
Prefork	Compatible with older applications, more stable	High resource consumption, fewer concurrent connections	Servers with low traffic and using older applications
Worker	Low resource consumption, more concurrent connections	May have compatibility issues with older applications	Servers with medium traffic and using modern applications
Event	Lowest resource consumption, highest concurrent connections, KeepAlive optimization	May have compatibility issues with older applications	Servers with high traffic and using modern applications

Step-by-Step MPM Change (CentOS/RHEL Example):

Checking the Current MPM:
```
httpd -V | grep MPM
```
Changing the MPM (Ex: Switching to Event):
```
yum install httpd-event
```
(If necessary, remove other MPMs: yum remove httpd-prefork httpd-worker)
Restarting Apache:
```
systemctl restart httpd
```

Case Study: An e-commerce site was experiencing performance issues due to high traffic during peak campaign periods. Prefork MPM was being used. After switching to Event MPM, the server load decreased by 40% and page load times dropped from an average of 2 seconds to 0.8 seconds.

How to Optimize KeepAlive Settings?

KeepAlive keeps the TCP connection between the client and the server open, allowing multiple HTTP requests to be sent over the same connection. This eliminates the cost of establishing a new connection for each request and improves performance. However, misconfiguring KeepAlive settings can unnecessarily consume server resources and negatively impact performance.

Important KeepAlive Settings:

KeepAlive: On or Off.
KeepAliveTimeout: The duration the connection remains open (seconds).
MaxKeepAliveRequests: The maximum number of requests that can be sent over a connection.

Recommended Settings:


KeepAlive On
KeepAliveTimeout 5
MaxKeepAliveRequests 100

Notes:

KeepAlive On: Enables the KeepAlive feature.
KeepAliveTimeout 5: The connection is closed if it is not active for 5 seconds. A shorter time allows the server to use resources more efficiently.
MaxKeepAliveRequests 100: A maximum of 100 requests can be sent over one connection. This prevents the server from being overloaded.

Step-by-Step KeepAlive Configuration:

Opening the Apache Configuration File:
```
nano /etc/httpd/conf/httpd.conf
```
(or /etc/apache2/apache2.conf)
Finding or Adding KeepAlive Settings:
Add the recommended settings above or update the existing settings.
Restarting Apache:
```
systemctl restart httpd
```

Visual Explanation: (Textual Explanation)

Imagine a diagram. In the diagram, when the KeepAlive feature is off, a new TCP connection is established for each HTTP request. This causes a significant delay for a large number of requests. When the KeepAlive feature is on, a connection is established for the first request, and subsequent requests are sent over the same connection. This reduces latency and improves performance.

How to Optimize Apache Modules? How to Disable Unnecessary Modules?

Apache uses modules for various functions. However, each module consumes resources. Disabling unused or unnecessary modules reduces the server's resource consumption and improves performance. To determine which modules are needed, you need to analyze your website's needs.

Commonly Used Apache Modules:

mod_rewrite: Used for URL redirection and rewriting.
mod_ssl: Used for SSL/TLS encryption.
mod_deflate: Used for compression (Gzip).
mod_expires: Used for caching.
mod_headers: Used to manipulate HTTP headers.
mod_php: Used for PHP support. (PHP-FPM is recommended)

Disabling Unnecessary Modules:

To disable Apache modules, the a2dismod command is usually used (on Debian/Ubuntu systems). On CentOS/RHEL systems, you may need to manually disable module configuration files.

Step-by-Step Module Disabling (Debian/Ubuntu Example):

Identify Unnecessary Module: For example, let's assume the mod_info module is unnecessary.
Disable the Module:
```
a2dismod info
```
Restart Apache:
```
systemctl restart apache2
```

CentOS/RHEL Example:

Find the Module Configuration File: For example, find the mod_info.conf file. It is usually located in the /etc/httpd/conf.modules.d/ directory.
Rename or Delete the File: You can disable the file by renaming it (e.g., mod_info.conf.disabled) or delete it (be careful!).
Restart Apache:
```
systemctl restart httpd
```

Important Note: Before disabling modules, make sure it does not affect the functionality of your website. Accidentally disabling an important module may cause your website to not work.

How to Do Caching? What Caching Methods Are Available?

Caching is one of the most effective methods to improve the performance of your website. Caching allows static content (images, CSS files, JavaScript files, etc.) to be stored on the client side (browser) or on a cache server instead of the server. This reduces the load on the server and shortens loading times.

Different Caching Methods:

Browser Caching: Web browsers store static content locally. This prevents the same content from being downloaded repeatedly.
Server-Side Caching: The server caches dynamic content (results of database queries, templates, etc.). This reduces the database load and shortens response times.
CDN (Content Delivery Network): CDNs store your website's content on servers around the world. This allows users to access content faster, especially in geographically remote regions.
Object Caching (Memcached, Redis): Especially for dynamic websites, it is used to store the results of database queries or other frequently accessed data in RAM.

Browser Caching with Apache (mod_expires and mod_headers):

The mod_expires and mod_headers modules are used to configure browser caching.

Step-by-Step Browser Caching Configuration:

Enabling the mod_expires Module: (If necessary)
```
a2enmod expires
```
Editing the Apache Configuration File: .htaccess or httpd.conf

Adding Caching Rules:


<IfModule mod_expires.c>
  ExpiresActive On
  ExpiresByType image/jpeg "access plus 1 year"
  ExpiresByType image/gif "access plus 1 year"
  ExpiresByType image/png "access plus 1 year"
  ExpiresByType text/css "access plus 1 month"
  ExpiresByType application/javascript "access plus 1 month"
</IfModule>

Restarting Apache:
```
systemctl restart apache2
```

Explanation:

ExpiresActive On: Enables the caching feature.
ExpiresByType: Defines caching durations for specific file types. For example, image/jpeg files are cached for 1 year.

How to Perform Compression? What is the Difference Between Gzip and Brotli?

Compression reduces the size of web pages, decreasing bandwidth usage and shortening loading times. Gzip and Brotli are two popular algorithms used to compress web pages. Brotli is a newer and more effective compression algorithm compared to Gzip.

Compression Algorithm	Advantages	Disadvantages	Suitable Situations
Gzip	Widely supported, easy to configure	Lower compression ratio compared to Brotli	Situations where older browsers need to be supported
Brotli	Higher compression ratio, faster loading times	Less widespread support, higher CPU consumption	Situations targeting modern browsers where performance is critical

Gzip Compression with Apache (mod_deflate):

Step-by-Step Gzip Configuration:

Enabling the mod_deflate Module:
```
a2enmod deflate
```
Editing the Apache Configuration File: .htaccess or httpd.conf

Adding Compression Rules:


<IfModule mod_deflate.c>
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/xml
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/atom+xml
</IfModule>

Restarting Apache:
```
systemctl restart apache2
```

Brotli Compression with Apache (mod_brotli):

Brotli is an algorithm that provides newer and better compression compared to Gzip. It is used with the mod_brotli module in Apache.

Step-by-Step Brotli Configuration:

Installing and Enabling the mod_brotli Module:
```
a2enmod brotli
```
Editing the Apache Configuration File: .htaccess or httpd.conf

Adding Brotli Compression Rules:


<IfModule mod_brotli.c>
    AddOutputFilterByType BROTLI_COMPRESS text/html text/plain text/xml text/css application/javascript application/x-javascript application/xml application/json
    BrotliFilterQuality 11
    BrotliFilterLength 512
</IfModule>

Restarting Apache:
```
systemctl restart apache2
```

Important Note: Brotli may not be supported by older browsers. Therefore, using both Gzip and Brotli together can provide the best result. This allows modern browsers to use Brotli, while older browsers use Gzip.