What is Entry Process (EP) Limit

To prevent DDos attacks on web servers, the Entry Proccess technology was created - a restriction on the number of input processes, the amount of PHP scripts executed simultaneously. One of the most well-known attacks on a web server is creating multiple HTTP connections that can slow down and disrupt the server's operation. The entry process limit or the limit on the number of concurrent Apache connections is created to mitigate DDos attacks on the server. As soon as the number of concurrent connections reaches its limit, the server issues a page with the error "Resource limit reached 508."

Many people confuse input processes with the number of visitors that can be attracted to a website - this is not the case. The hosting we offer includes:

• limit on concurrent EP connections;
• limit on the number of active processes.

The concept of limited restriction on the number of active processes is clear - it allows functioning for the maximum number of processes specified in the limitation. After all Apache slots are used up, new connections to the server become impossible, leading to its disconnection. In this case, the central processor load will be high, and the Apache page serving speed will be low.

Entry Proccess (EP Connections) Operating Principle

CloudLinux is the most popular operating system for hosting, as Entry Proccess is one of its configurations for the Lightweight Virtual Environment (LVE) feature. The Entry Proccess technology controls the maximum number of entries into the LVE virtual environment. This means that the increase in the EP counter depends on each individual visitor or process in the virtual environment, and the decrease in the EP counter depends on each visitor or process exiting the LVE.

The limit of input processes for a web hosting account is the maximum number of simultaneously running processes that the hosting account can handle. In general, accessing the web server ends instantly, and exceeding the Entry Proccess limit does not occur, so even 110 connections per second cannot affect the website's performance.

Any request to the web server that occurs through PHP generates an LSPHP process - the handler returns the query result to the client's browser. If there are no problems with the account, the process is completed in just 250-300ms. Delaying the process completion for 1 second leads to an increase in the number of launched EP connections by 1. Then each subsequent request to the server will result in processes that have been running for more than 1 second. When the counter reaches the limit specified in the functionality, the resource will crash.

So, if the login process limit for your hosting is 20, this means that 20 visitors can simultaneously open your portal in fractions of a second. Such a limitation is optimal for the correct functioning of the processor and scripts, which will allow you to smoothly serve about 1.2 million visitors per day.

Problems arise in several cases:

• slow processor performance;
• maximum load on the account's processor, due to which processes launched through the web server are processed very slowly;
• the appearance of a variety of DDos attacks - http-flood - a huge number of requests to the site per second;
• additional processes launched by a PHP script.

Those who want to study the principle of the Entry Proccess technology more thoroughly can familiarize themselves with the official CloudLinux documentation.