Understand CGI and fastcgi

CGI

CGI(Common Gateway Interface) Public gateway interface ,CGI It's a protocol . To be exact ,CGI It's the app ( Such as PHP) And Web A standard interface for server interaction 、 agreement .

• according to CGI standard , Write applications , It can process the data input by the client , Complete the interaction between the client and the server ;
• CGI Defined Web How the server sends messages to the extended application , How to process the application information after receiving it ;

Let's understand the above content through a picture ：

 

• CGI yes Web The server and Web Applications (php/python etc. ) A protocol for data interaction between ;
• FastCGI And CGI equally , It's also Web The server and Web A protocol for application interaction , It's just FastCGI In terms of efficiency CGI Better ;

CGI Implementation principles and problems

• CGI The program runs in a separate process , And each Web Requests create a process , Destroy at the end . such “ One new process per request ” bring CGI Poor efficiency , Difficult to expand ;
• Under high load , The operating system overhead for process creation and destruction becomes significant ;
• Because the process address space cannot be shared ,CGI The process model limits the reuse of methods , Such as reusing database links ;

FastCGI

Fast universal Gateway Interface (Fast Common GateWay Interface) And CGI equally , It is also a way to make the application and Web Protocol of server communication .FastCGI yes CGI Enhanced version of .

• FastCGI Less Web The server and CGI The cost of interaction between programs , This enables the server to process more web requests at the same time .

Realization

• FastCGI Use persistent processes to process requests , These processes are made up of FastCGI Server management , instead of Web The server .
• FastCGI Like a resident (long-live) Type CGI, It can be carried out all the time , No process creation and termination overhead per request .

FastCGI working principle

1. Web Load when the server starts FastCGI Process Manager ( Such as PHP-FPM);
2. FastCGI Process manager initialization itself , Start multiple CGI Interpreter process and wait for from Web Server connection ;
3. When a client request arrives Web Server time ,FastCGI The process manager selects and connects to a CGI Interpreter .Web The server passes the environment variable and the page request through a socket or TCP connection Pass to FastCGI Subprocesses ;
4. FastCGI After the subprocess finishes processing, standard output and error information are returned from the same connection Web Server. When FastCGI When the child process closes the connection , Request processing completed .FastCGI The subprocess then waits and processes from FastCGI Process Manager ( Running on the Web Server in ) Next connection for .

PHP-CGI

php-cgi yes php Self contained FastCGI Manager .

php-cgi Deficiency

• php-cgi It's changing php.ini Restart after configuration php-cgi To make a new php.ini take effect , Failed to restart smoothly ;
• Kill directly php-cgi process ,php Can't run ;

PHP-FPM

php-fpm yes PHP FastCGI Manager .FastCGI Just a protocol specification , Each language needs to implement ,PHP-FPM Namely PHP Version of FastCGI Protocol implementation .

• Support smooth restart , After receiving the restart signal , First kill Idle worker process , new worker With the new configuration ;
• The pressure can be increased or decreased dynamically according to the request worker Number of processes ;