Memory Error Handling
- Memory Error Handling in MediaWiki 1.40
This article details memory error handling for MediaWiki 1.40 server environments. Proper configuration and understanding of these mechanisms are crucial for maintaining a stable and performant wiki. We will cover common causes, detection methods, and mitigation strategies. This guide is intended for system administrators and experienced wiki operators.
Understanding Memory Errors
Memory errors in a MediaWiki environment can manifest in several ways, ranging from minor performance degradation to complete server crashes. These errors are often caused by insufficient memory allocation, memory leaks within PHP code or extensions, or hardware failures. Identifying the root cause is the first step in resolving these issues. Common symptoms include:
- Slow page loading times
- PHP errors related to memory exhaustion (e.g., "Allowed memory size of X bytes exhausted")
- Web server (e.g., Apache, Nginx) crashes
- Database connection issues due to server instability
- Unexpected blank pages or incomplete content
Common Causes of Memory Errors
Several factors can contribute to memory errors. Understanding these helps in proactive prevention.
- **High Traffic:** Increased user activity naturally consumes more memory.
- **Complex Pages:** Pages with many images, templates, or parser functions require more memory to render. See Help:Templates for more information.
- **Memory Leaks:** Bugs in PHP code or extensions can lead to memory being allocated but never freed.
- **Insufficient PHP Memory Limit:** The `memory_limit` setting in `php.ini` might be too low for the wiki’s needs. Refer to Manual:Configuration settings for details.
- **Hardware Issues:** Failing RAM modules can cause unpredictable memory errors.
- **Extension Conflicts:** Incompatible or poorly written extensions can consume excessive memory. Refer to Manual:Extensions for more details.
Detection and Monitoring
Proactive monitoring is vital. Several tools and techniques can help detect memory errors:
- **Server Logs:** Check web server and PHP error logs for memory-related errors.
- **System Monitoring Tools:** Use tools like `top`, `htop`, or `vmstat` to monitor server memory usage.
- **PHP Memory Usage Functions:** Utilize PHP functions like `memory_get_usage()` and `memory_get_peak_usage()` within custom scripts or extensions to track memory consumption.
- **Slow Query Log:** High memory usage can be related to inefficient database queries. Analyze the Manual:Database slow query log.
- **Wiki Statistics:** Monitor page sizes and the number of revisions to identify potentially problematic content.
PHP Memory Limit Configuration
The PHP memory limit is a crucial setting.
| Parameter | Value | Description |
|---|---|---|
| `memory_limit` | 128M - 512M (or higher) | Maximum amount of memory a script may consume. Adjust based on wiki size and complexity. |
| `realpath_cache_size` | 32M - 128M | Cache for resolved file paths. Larger values can improve performance. |
| `realpath_cache_ttl` | 3600 | Time-to-live for cached file paths (in seconds). |
Edit your `php.ini` file (location varies depending on your operating system and web server configuration) to adjust the `memory_limit`. Restart your web server after making changes.
Mitigation Strategies
Once a memory error is detected, several strategies can be employed to mitigate the problem.
- **Increase PHP Memory Limit:** The simplest solution, but not always the most effective if a memory leak is present.
- **Optimize PHP Code:** Review custom PHP code and extensions for memory leaks or inefficient algorithms. Use a profiler to identify bottlenecks.
- **Optimize Database Queries:** Slow or inefficient database queries can consume significant memory. Use the Manual:Database explain plan to analyze and optimize queries.
- **Cache Pages:** Implement caching mechanisms (e.g., Extension:CacheHitRecount) to reduce the load on the server and memory usage.
- **Disable or Replace Problematic Extensions:** If a specific extension is identified as the source of the problem, disable it or find a more efficient alternative.
- **Hardware Upgrade:** If the server consistently runs out of memory, consider upgrading the RAM.
Recommended Server Specifications
The following table provides recommended server specifications based on wiki size and traffic.
| Wiki Size | Estimated Users | Recommended RAM | Recommended CPU |
|---|---|---|---|
| Small ( < 10,000 pages) | < 100 | 4GB - 8GB | Dual-Core Processor |
| Medium (10,000 - 100,000 pages) | 100 - 1000 | 8GB - 32GB | Quad-Core Processor |
| Large ( > 100,000 pages) | > 1000 | 32GB+ | Multi-Core Processor |
These are estimates, and actual requirements will vary based on specific wiki configuration and usage patterns.
Troubleshooting Table
| Symptom | Possible Cause | Solution |
|---|---|---|
| "Allowed memory size exhausted" error | PHP `memory_limit` too low | Increase `memory_limit` in `php.ini`. |
| Slow page loading times | Insufficient RAM, inefficient queries, un-cached pages | Upgrade RAM, optimize queries, enable caching. |
| Web server crashes | Severe memory exhaustion, hardware failure | Increase `memory_limit`, check server logs, test RAM. |
| Unexpected blank pages | Memory corruption, extension conflict | Review logs, disable extensions. |
Further Resources
- Manual:How to debug PHP
- Manual:Configuration settings
- Manual:Database
- Manual:Extensions
- Help:Templates
- Help:Speeding up your wiki
Intel-Based Server Configurations
| 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
| 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.* ⚠️