CGI, FastCGI, PHP-FPM

This article transferred from: http://segmentfault.com/q/1010000000256516

First of all, what does CGI do? CGI is designed to ensure that the data passed by the Web server is in a standard format and facilitates the writer of CGI programs.

Web server, such as Nginx, is simply the publisher of the content. For example, if the request /index.html , then the Web server will go to the file system to find this file, sent to the browser, here is distributed static data. Well, if the request is now /index.php , according to the configuration file, Nginx know that this is not a static file, need to find a PHP parser to deal with, then he will simply handle the request to the PHP parser. What data will the Nginx send to the PHP parser? URL to have it, query string also have to have, post data also have, HTTP header can not be less, good, CGI is to specify what data to pass, in what format to the rear processing the request of the Protocol. Think carefully about where the users you are using in your PHP code come from.

When the Web server receives /index.php this request, it launches the corresponding CGI program, which is the parser for PHP. The PHP parser then parses the php.ini file, initializes the execution environment, then processes the request, and then returns the processed result in a format specified by the CGI, exiting the process. The Web server then returns the results to the browser.

Well, CGI is a protocol, it doesn't matter what the process is. What is that fastcgi? FastCGI is used to improve the performance of CGI programs.

Improve performance, what is the performance problem with CGI programs? "The PHP parser parses the php.ini file, initializes the execution environment," and here it is. The standard CGI performs these steps for each request (no idle fatigue!). Start the process very tired to say! ), so it takes longer to process each time. This is obviously unreasonable! So how did fastcgi do it? First, fastcgi initiates a master, parses the configuration file, initializes the execution environment, and then starts multiple workers. When the request comes in, master passes it to a worker, and then immediately accepts the next request. This avoids duplication of labor, and efficiency is naturally high. And when the worker is not enough, master can pre-boot several workers according to the configuration and so on, of course, the idle worker too much, will also stop some, this improves the performance, also saves the resources. This is FastCGI's management of the process.

What is that php-fpm? is a realization of the FASTCGI program, by the PHP official received.

As we all know, PHP's interpreter is php-cgi. PHP-CGI is just a CGI program, he himself can only parse the request, return the results, will not process management (the emperor, my concubine really do not AH!) So there are some programs that can dispatch php-cgi processes, such as spawn-fcgi separated by LIGHTHTTPD. Well php-fpm is such a thing, after a long period of development, gradually got everyone's approval (to know, in the previous few years everyone complained php-fpm stability is too poor), but also more and more popular.

Some on the internet say that fastcgi is an agreement, and PHP-FPM realizes this agreement.

Some say that PHP-FPM is the manager of the fastcgi process, used to manage the fastcgi process.

Right. The management object of PHP-FPM is php-cgi. But it cannot be said that PHP-FPM is the manager of the fastcgi process, because the fastcgi is a protocol, it seems that no such process exists, even if there is php-fpm can not manage him (at least for now).

Some say that php-fpm is a patch for the PHP kernel.

Used to be right. Because PHP-FPM is not included in the PHP kernel at the beginning, to use this function, we need to find the same version of the source code php-fpm the kernel patch, and then compile. Later, after the PHP kernel integrates php-fpm, it is much easier to use --enalbe-fpm this compilation parameter.

Some said that after modifying the php.ini configuration file, there is no way to smooth the restart, so the birth of PHP-FPM.

Yes, after modifying php.ini, the php-cgi process does not have the means to smooth the restart. PHP-FPM This mechanism is the new worker with a new configuration, the already existing workers can rest after processing the hands of the work, through this mechanism to smooth over.

Some say that php-cgi is the FastCGI manager that comes with PHP, so why get a php-fpm out again.

Wrong. PHP-CGI is just a program that explains PHP scripts.

(RPM) CGI, FastCGI, PHP-FPM