Apache affords quite a lot of multi-processing modules. These are also referred to as MPMs, and are liable for figuring out the way to deal with consumer requests. This permits directors to change its connection dealing with structure merely, shortly, and conveniently.

So, what are these modules?

mpm-prefork

This Apache module creates processes with one thread to deal with every request, and each baby is ready to accommodate one connection at one time. Supplied the amount of requests stays lower than that of processes, this module is able to extraordinarily quick efficiency.

However it might display a severe drop in high quality when the variety of requests passes the variety of processes, which implies this module isn’t at all times the correct possibility.

Each course of with this module has a significant impact on the consumption of RAM, too, which makes it onerous to realize efficient scaling. Nonetheless, it might nonetheless be a stable selection when utilized alongside extra elements constructed with out consideration of threads. E.g. as PHP lacks thread security, this module could possibly be one of the simplest ways to work with mod_php (Apache’s module for processing these particular information) safely.

mpm_worker

Apache’s mpm_worker module is designed to spawn processes able to managing quite a few threads every, with every of these dealing with one connection. Threads show extra environment friendly than processes, so this MPM affords stronger scaling than the module mentioned above.

As there are not any extra threads than processes, recent connections can take up one of many free threads reasonably than ready for one more appropriate course of to return alongside.

mpm_event

Apache’s third module may be thought of just like the aforementioned mpm_worker module within the majority of conditions, although it’s been optimised to accommodate keep-alive connections. Because of this, when utilizing the employee module, connections proceed to carry threads, whether or not or not requests are made actively for the complete interval throughout which the connection stays alive.

It’s clear that Apache’s connection dealing with structure affords appreciable flexibility when choosing numerous connections and request-handling algorithms. Choices supplied are primarily a results of the server’s continued development, in addition to the rising demand for concurrency because the web has modified so dramatically.