The Apache HTTP Server is a widely-used open-source web server that provides high performance and stability. It supports various Multi-Processing Modules (MPMs), including the Prefork and Worker MPMs, which handle incoming connections and serve dynamic content. When it comes to choosing the right MPM for your web server, it’s important to understand the differences between Prefork and Worker MPMs. In this article, we will compare the two MPMs and explore the key factors to consider when making a decision between them. Whether you’re a beginner or an experienced Linux administrator, this article will provide valuable insight into the Apache HTTP Server and help you choose the best MPM for your needs.
In this tutorial you will learn:
- Overview of Linux Apache Prefork and Worker MPMs
- Differences between Prefork and Worker MPMs
- Pros and Cons of using Prefork and Worker MPMs
- Considerations for choosing between Prefork and Worker MPMs for specific use cases
| Category | Requirements, Conventions or Software Version Used |
|---|---|
| System | Distribution independent |
| Software | apache 2 webserver |
| Other | Administrative privileges are needed to install required packages |
| Conventions | # – requires given linux-commands to be executed with root privileges either directly as a root user or by use of sudo command $ – requires given linux-commands to be executed as a regular non-privileged user |
Definition of Prefork and Worker MPMs in Apache
When it comes to configuring Apache on a Linux server, there are two main Multi-Processing Modules (MPMs) that can be used: Prefork and Worker. Both MPMs determine how Apache handles incoming requests and how it utilizes system resources. In this article, we’ll explore the key differences between Prefork and Worker MPMs to help you determine which one is best suited for your needs.
The Prefork MPM is the traditional MPM that has been around since the early days of Apache. It is a preforking server that creates a number of child processes, each of which can handle a single request at a time. This allows Apache to handle multiple requests simultaneously without having to create a new process for each request. However, this also means that each child process uses a significant amount of memory, which can be a problem for large, busy sites.
The Worker MPM, on the other hand, uses a threaded approach, with each child process handling multiple requests simultaneously using multiple threads. This reduces the amount of memory used by Apache, as each child process can handle many requests with only one set of memory overhead. However, this also means that Apache must be configured to use thread-safe modules and that each request is processed in a separate thread, which can result in a slight performance overhead.
Comparison of Prefork and Worker MPMs in terms of performance, resource usage and scalability
When comparing the Prefork and Worker MPMs in Apache, it is important to consider their performance, resource usage, and scalability. The Prefork MPM is designed to handle multiple clients at once, and each child process handles one connection at a time. This design is ideal for low traffic sites or sites that require compatibility with modules that do not support the worker MPM. On the other hand, the Worker MPM is optimized for high traffic sites and uses multiple worker threads to handle multiple clients at once. This design allows for better performance and scalability in comparison to the Prefork MPM.
When it comes to resource usage, the Worker MPM typically requires more memory than the Prefork MPM due to the use of multiple threads. However, this increased memory usage allows the Worker MPM to handle more clients simultaneously, leading to better overall performance. Additionally, the Worker MPM has the ability to spawn new worker threads on-demand, which helps to improve scalability.
In terms of performance, the Worker MPM outperforms the Prefork MPM in high traffic scenarios due to its ability to handle multiple clients simultaneously. The Worker MPM also has the ability to cache connections and content, leading to faster page load times.
Overall, the choice between the Prefork and Worker MPMs largely depends on the specific needs of your site. For low traffic sites or sites with compatibility requirements, the Prefork MPM may be the best option. For high traffic sites, the Worker MPM offers improved performance and scalability.
Use cases for Prefork and Worker MPMs
In Apache, the choice of MPM (Multi-Processing Module) depends on the specific use case and requirements of the web server. The Prefork MPM, which creates a separate process for each incoming connection, is best suited for environments where stability is a priority, such as servers serving CGI scripts. On the other hand, the Worker MPM, which uses multiple worker threads to handle incoming connections, is more efficient in terms of resource usage and is better suited for high-traffic web sites and high-performance applications.
When it comes to performance, the Worker MPM has an edge over the Prefork MPM as it can handle more requests per second due to its multi-threaded design. However, this comes with a trade-off in terms of memory usage, as each worker thread requires a certain amount of memory. The Prefork MPM, on the other hand, uses less memory but is limited in terms of the number of requests it can handle at any given time.
Scalability is another factor to consider when choosing between Prefork and Worker MPMs. In general, the Worker MPM is more scalable as it can handle an increasing number of incoming connections more efficiently than the Prefork MPM. This makes it an ideal choice for web servers that need to handle high traffic loads.
It’s important to note that the choice of MPM should not be taken lightly, as it can have a significant impact on the performance and stability of the web server. Before making a decision, it’s recommended to thoroughly evaluate the specific requirements and use cases of the web server, as well as to perform benchmark tests to determine the optimal configuration.
Configuration of Prefork and Worker MPMs in Apache
The configuration of Prefork and Worker MPMs in Apache is done through the Apache configuration file, typically located at/etc/httpd/conf/httpd.conf. The following are example configuration file excerpts for both Prefork and Worker MPMs in Apache.<IfModule mpm_prefork_module>
StartServers 8
MinSpareServers 5
MaxSpareServers 20
ServerLimit 256
MaxRequestWorkers 256
MaxConnectionsPerChild 0
</IfModule><IfModule mpm_worker_module>
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>- StartServers: Specifies the number of child server processes created at startup.
- MaxClients: Specifies the maximum number of clients that can be connected simultaneously to the Apache server.
- MinSpareThreads: Specifies the minimum number of spare worker threads that should be available at any time.
- MaxSpareThreads: Specifies the maximum number of spare worker threads that should be available at any time.
- ThreadsPerChild: Specifies the number of worker threads created by each child process in the server.
- MaxRequestsPerChild: Specifies the number of requests each child process should handle before terminating and being replaced by a new child process.
Benefits and limitations of Prefork and Worker MPMs in Linux Apache webserver
The Apache HTTP Server is a powerful and flexible web server that can be configured in various ways to meet the needs of different use cases. Two of the most commonly used MPMs (Multi-Processing Modules) in Apache are the Prefork MPM and the Worker MPM. In this section, we will explore the benefits and limitations of each of these MPMs in the context of the Apache web server.
The Prefork MPM is designed to handle multiple incoming connections by creating multiple processes, each of which can handle a single connection at a time. This design is best suited for applications that require a high degree of stability and robustness, as it ensures that a single client request cannot crash the entire server. Additionally, since each process runs in its own memory space, there is a reduced risk of one client’s request affecting the performance of another.
On the other hand, the Worker MPM is designed to handle multiple connections using multiple threads within a single process. This design is more resource-efficient than the Prefork MPM, as it requires less memory and can handle more connections simultaneously. However, this design also means that a single client request has the potential to crash the entire server, so it may not be suitable for applications that require a high degree of stability.
In terms of performance, the Worker MPM generally performs better than the Prefork MPM, especially under heavy load. This is because the Worker MPM can handle multiple connections simultaneously, while the Prefork MPM can only handle one connection at a time.
Best practices for choosing between Prefork and Worker MPMs in different deployment scenarios
Choosing the right MPM (Multi-Processing Module) for your Apache server can greatly impact its performance, resource usage, and scalability. Prefork and Worker MPMs are two of the most commonly used options in Linux Apache deployments. In this section, we will explore some best practices for choosing between Prefork and Worker MPMs based on different deployment scenarios.
For small to medium-sized sites, Prefork MPM is a good choice. It creates a separate process for each incoming request, making it a solid option for deployments with low to moderate traffic levels. Prefork MPM is also a good choice for deployments that require compatibility with non-thread-safe code or modules.
For high-traffic sites and large-scale deployments, Worker MPM is often a better choice. Worker MPM uses a thread-based model, which is more efficient in terms of memory usage and can handle a much higher number of connections simultaneously. This makes it a better choice for large-scale, high-traffic deployments.
In deployments where a combination of static and dynamic content is served, it may be best to use a combination of both Prefork and Worker MPMs. The Prefork MPM can be used to serve static content, while the Worker MPM can handle dynamic content.
Conclusion
In conclusion, choosing between the Linux Apache Prefork and Worker MPMs is a critical decision for any Apache deployment, as it affects the performance, resource usage, and scalability of the web server. Both MPMs have their own benefits and limitations, and the best choice depends on the specific use case and deployment scenario. It is important to understand the differences between Prefork and Worker MPMs and to carefully consider the factors that influence their performance and suitability for different deployment scenarios. By taking the time to understand the differences between Prefork and Worker MPMs and to carefully consider their best practices, you can ensure that you make the right choice for your Apache deployment.
