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Automated server configuration article

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# Load Balancing for MediaWiki

This article details load balancing configurations for a MediaWiki 1.40 installation. Load balancing distributes network and application traffic across multiple servers, enhancing performance, reliability, and availability. It's a crucial component for any high-traffic MediaWiki site. This guide is intended for newcomers to server administration and assumes a basic understanding of web servers and databases.

== What is Load Balancing? ==

Imagine a single doorway to a popular concert. Everyone has to go through that one door, causing a bottleneck. Load balancing is like adding multiple doorways, allowing more people to enter simultaneously. In the context of MediaWiki, multiple web servers deliver web pages to users, and a load balancer distributes the requests among them. If one server fails, the load balancer automatically redirects traffic to the remaining healthy servers, ensuring continuous service.

== Why Use Load Balancing with MediaWiki? ==

Several benefits drive the need for load balancing in a MediaWiki environment:

* '''Increased Availability:''' If one server goes down, the others continue to handle requests.
* '''Improved Performance:''' Distributing the load reduces response times and improves the user experience.
* '''Scalability:''' Easily add more servers to handle growing traffic without impacting existing users.
* '''Reduced Downtime:''' Maintenance can be performed on servers one at a time without taking the entire site offline.

== Common Load Balancing Techniques ==

Several methods are used for load balancing. These include:

* '''Round Robin:''' Requests are distributed sequentially to each server.
* '''Least Connections:''' Requests are sent to the server with the fewest active connections.
* '''IP Hash:''' The client's IP address is used to determine which server receives the request. This ensures a user consistently connects to the same server (important for sessions).
* '''URL Hash:''' The requested URL is used to determine the server.
* '''Weighted Load Balancing:''' Servers are assigned weights based on their capacity.

== Software and Hardware Options ==

Both software and hardware load balancers are available.

* '''Hardware Load Balancers:''' Dedicated appliances offering high performance and reliability. Examples include F5 Networks BIG-IP and Citrix ADC. These are generally more expensive.
* '''Software Load Balancers:''' Software running on standard servers. Common options include:
* '''HAProxy:''' A popular, open-source load balancer.
* '''Nginx:''' A versatile web server that can also function as a load balancer. See [[Nginx configuration]] for details.
* '''Apache:''' Can be configured for basic load balancing, but less common than HAProxy or Nginx. See [[Apache web server]] for details.
* '''Keepalived:''' Primarily for virtual IP address management and failover, often used in conjunction with other load balancing solutions. See [[Keepalived setup]].

== Example Configuration: HAProxy ==

This section outlines a basic HAProxy configuration for load balancing two MediaWiki servers. Assume two servers: `mediawiki1.example.com` and `mediawiki2.example.com`.

Here’s a sample `haproxy.cfg` file:

```
frontend mediawiki_frontend
bind *:80
mode http
default_backend mediawiki_backend

backend mediawiki_backend
mode http
balance roundrobin
server mediawiki1.example.com:80 check
server mediawiki2.example.com:80 check
```

This configuration listens on port 80 and distributes requests using the round-robin method to the two MediaWiki servers. The `check` option periodically verifies the health of each server. See [[HAProxy documentation]] for more advanced configuration options.

== Server Specifications ==

The following table outlines recommended server specifications for MediaWiki load balancing:

{| class="wikitable"
! Server Role
! CPU
! RAM
! Storage
! Operating System
|-
| Web Server (MediaWiki)
| 4+ Cores
| 8GB+
| 100GB+ SSD
| Linux (Ubuntu, CentOS, Debian)
|-
| Load Balancer (HAProxy/Nginx)
| 2+ Cores
| 4GB+
| 50GB+ SSD
| Linux (Ubuntu, CentOS, Debian)
|-
| Database Server
| 8+ Cores
| 16GB+
| 500GB+ SSD
| Linux (Ubuntu, CentOS, Debian)
|}

== Database Considerations ==

Load balancing the web servers does *not* automatically load balance the database. The MediaWiki servers will all be connecting to the same database server. For high availability, consider:

* '''Database Replication:''' Set up a read-only replica of your database. Web servers can read from the replica, reducing load on the primary database. See [[Database replication]].
* '''Database Clustering:''' More complex, but provides higher availability and scalability.
* '''Solid State Drives (SSDs):''' Essential for database performance.

== Session Management ==

Proper session management is critical when using load balancing. If a user is directed to one server, they need to remain on that server for the duration of their session. Several options exist:

* '''Sticky Sessions (IP Hash):''' As mentioned earlier, uses the client's IP address to ensure consistent routing. However, this can be problematic with shared IP addresses (e.g., behind a proxy).
* '''Session Storage in Database:''' Store session data in a shared database accessible by all web servers. This is the most reliable method. See [[Session management]].
* '''Shared Filesystem:''' Use a shared filesystem (e.g., NFS) to store session data. Less common due to potential performance and reliability issues.

== Monitoring and Logging ==

Monitoring your load balancing setup is essential for identifying and resolving issues. Key metrics to monitor include:

* '''Server Load:''' CPU usage, memory usage, disk I/O.
* '''Request Rate:''' Requests per second.
* '''Response Time:''' Average time to serve a request.
* '''Error Rate:''' Number of errors.

Use tools like:

* '''Nagios:''' A comprehensive monitoring system. See [[Nagios configuration]].
* '''Zabbix:''' Another popular monitoring solution.
* '''Prometheus:''' A systems monitoring and alerting toolkit.
* '''HAProxy Stats Page:''' Provides real-time statistics about your HAProxy configuration.

The following table summarizes common log files to monitor:

{| class="wikitable"
! Log File
! Location
! Purpose
|-
| Access Log
| Web Server (e.g., /var/log/apache2/access.log)
| Records all incoming requests
|-
| Error Log
| Web Server (e.g., /var/log/apache2/error.log)
| Records errors and warnings
|-
| HAProxy Log
| /var/log/haproxy.log (or configured location)
| Records HAProxy statistics and errors
|}

== Troubleshooting ==

* '''Server Down:''' Verify the server is running and accessible. Check the web server error logs.
* '''Slow Response Times:''' Investigate server load, database performance, and network latency.
* '''Session Issues:''' Ensure session management is configured correctly. Verify sticky sessions are working as expected or that shared session storage is accessible.
* '''Load Imbalance:''' Check the load balancer configuration and ensure servers are properly weighted.

== Further Resources ==

* [[MediaWiki Installation guide]]
* [[Database setup]]
* [[Server security]]
* [[Caching strategies]]
* [[Performance tuning]]

[[Category:Server Hardware]]

== Intel-Based Server Configurations ==
{| class="wikitable"
! Configuration
! Specifications
! Benchmark
|-
| [[Core i7-6700K/7700 Server]]
| 64 GB DDR4, NVMe SSD 2 x 512 GB
| CPU Benchmark: 8046
|-
| [[Core i7-8700 Server]]
| 64 GB DDR4, NVMe SSD 2x1 TB
| CPU Benchmark: 13124
|-
| [[Core i9-9900K Server]]
| 128 GB DDR4, NVMe SSD 2 x 1 TB
| CPU Benchmark: 49969
|-
| [[Core i9-13900 Server (64GB)]]
| 64 GB RAM, 2x2 TB NVMe SSD
|
|-
| [[Core i9-13900 Server (128GB)]]
| 128 GB RAM, 2x2 TB NVMe SSD
|
|-
| [[Core i5-13500 Server (64GB)]]
| 64 GB RAM, 2x500 GB NVMe SSD
|
|-
| [[Core i5-13500 Server (128GB)]]
| 128 GB RAM, 2x500 GB NVMe SSD
|
|-
| [[Core i5-13500 Workstation]]
| 64 GB DDR5 RAM, 2 NVMe SSD, NVIDIA RTX 4000
|
|}

== AMD-Based Server Configurations ==
{| class="wikitable"
! Configuration
! Specifications
! Benchmark
|-
| [[Ryzen 5 3600 Server]]
| 64 GB RAM, 2x480 GB NVMe
| CPU Benchmark: 17849
|-
| [[Ryzen 7 7700 Server]]
| 64 GB DDR5 RAM, 2x1 TB NVMe
| CPU Benchmark: 35224
|-
| [[Ryzen 9 5950X Server]]
| 128 GB RAM, 2x4 TB NVMe
| CPU Benchmark: 46045
|-
| [[Ryzen 9 7950X Server]]
| 128 GB DDR5 ECC, 2x2 TB NVMe
| CPU Benchmark: 63561
|-
| [[EPYC 7502P Server (128GB/1TB)]]
| 128 GB RAM, 1 TB NVMe
| CPU Benchmark: 48021
|-
| [[EPYC 7502P Server (128GB/2TB)]]
| 128 GB RAM, 2 TB NVMe
| CPU Benchmark: 48021
|-
| [[EPYC 7502P Server (128GB/4TB)]]
| 128 GB RAM, 2x2 TB NVMe
| CPU Benchmark: 48021
|-
| [[EPYC 7502P Server (256GB/1TB)]]
| 256 GB RAM, 1 TB NVMe
| CPU Benchmark: 48021
|-
| [[EPYC 7502P Server (256GB/4TB)]]
| 256 GB RAM, 2x2 TB NVMe
| CPU Benchmark: 48021
|-
| [[EPYC 9454P Server]]
| 256 GB RAM, 2x2 TB NVMe
|
|}

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

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