CGI,FastCGI,PHP-CGI,PHP-FPM,Spawn-FCGI

上面是英文，下面有中文解释。

CGI

• CGI, Common Gateway Interface, is a tool for HTTP server to contact with programs on other servers, which can be used into any languages with standard input, standard output and environmental variables, such as PHP, Perl, or Tcl.

FastCGI

• FastCGI is a kind of CGI which is long-live, which will always be running. With FastCGI, it'll take less time t fork(which is a problem of fork-and-execute mode in CGI). In additional, FastCGI also supports for distributed computing.

• It is also not language related, which is an opened extension of CGI, which is used to keep CGI running in the memory. It's well-known that loading of CGI has been the main reason of low performance.

• the main process of running FastCGI:

  1. Loading the Process Manager of FastCGI when a Web server has booted(IIS ISAPI or Apache Module)
  2. The Process Manager of FastCGI will initiate itself to create several CGI processes, which are used to wait for connection of Web servers.
  3. When requests from clients have reached the Web server, the Process Manager of FastCGI will select a CGI set up before to connect, whose environmental variables and standard input will be sent to the sub process php-cgi of FastCGI.
  4. This sub process will return standard output and error info to the Web server with the same connection. Requests will be finished when it closes the connection.
• Therefore, FastCGI only set once for parsing php.ini, loading extensions and initiating all the data structures.

shortcuts

• Because of multi-processes, FastCGI will cost more memory than CGI, whose each process(PHP-CGI) will cost about 7Mb to 25Mb memory.

• Data from the article: Nginx 0.8x + PHP 5.2.13(FastCGI) is 10 times better than Apache(Edition 6)
• when 30k connection happens in parallel, 10 Nginx processes will only cost 150Mb Mem(15Mb 10), and 64 PHP-CGI will only cost about 1280Mb(20Mb 64).

PHP-CGI

• PHP-CGI is one kind of the Process Manager of FastCGI, which is within php itself.
• The command to boot is as follow:

php-cgi -b 127.0.0.1:9000

shortcuts

• After changing php.ini, you should reboot PHP-CGI to make the new php.ini work.
• When a PHP-CGI process is killed, all the PHP code will cannot run.(PHP-FPM and Spawn-FCGI do not have the same problem)

PHP-FPM(Fast-CGI Process Manager)

• PHP-FPM is another kind of the Process Manager of FastCGI, which can be downloaded here.
• It's actually a patch for PHP, which is used to integrate the Process Manager of FastCGI into PHP, which should be make into PHP before version 5.3.2(5.3.2之后已经集成于php中).
• PHP-FPM can be used to control sub processes of PHP-CGI:

/usr/local/php/sbin/php-fpm [options] # options # --start: start a fastcgi process of php # --stop: force to kill a fastcgi process of php # --quit: smooth to kill a fastcgi process of php # --restart: restart a fastcgi process of php # --reload: smooth to reload php.ini # --logrotate: enable log files again 

Spawn-FCGI

• Spawn-FCGI is a general kind of the Process Manager of FastCGI， which is one part of lighttpd.

 

 

做者：auxten
连接：https://www.zhihu.com/question/30672017/answer/49817021
来源：知乎
著做权归做者全部。商业转载请联系做者得到受权，非商业转载请注明出处。

CGI（Common Gateway Interface）

最初，CGI 是在 1993 年由美国国家超级电脑应用中心（NCSA）为 NCSA HTTPd Web 服务器开发的。

这个 Web 服务器使用了 UNIX shell 环境变量 来保存从 Web 服务器传递出去的参数，而后生成一个运行 CGI 的独立进程。CGI的第一个实现是 Perl 写的[1]。

• 效率低下：每个链接 fork 一个进程处理。
• 功能十分有限：CGI只能收到一个请求，输出一个响应。很难在CGI体系去对Web请求的控制，例如：用户认证等。

正由于这些问题，在CGI诞生后的很长一段时间，各类Web Server都仍是采用API这种强绑定的方式去支持Web开发，其中Apache的mod_php就属于这种方式。因此后面就有大神提出了FastCGI标准。

FastCGI（Fast Common Gateway Interface）

FastCGI使用进程/线程池来处理一连串的请求。这些进程/线程由FastCGI服务器管理，而不是Web服务器。 当进来一个请求时，Web服务器把环境变量和这个页面请求经过一个Socket长链接传递给FastCGI进程。因此FastCGI有以下的优势：

• 性能：经过进程/线程池规避了CGI开辟新的进程的开销。
• 兼容：很是容易改造现有CGI标准的程序。
• 语言无关：FastCGI是一套标准，理论上讲只要能进行标准输出（stdout）的语言均可以做为FastCGI标准的Web后端。
  下面是一个简单FastCGI后端的伪代码

void main(void)
{
int count = 0;
  while(FCGI_Accept() >= 0) {
    printf(“Content-type: text/html\r\n”);
    printf(“\r\n”);
    printf(“Hello world!\r\n”);
    printf(“Request number %d.”, count++);
  }
exit(0);
}

• Web Server隔离：FastCGI后端和Web Server运行在不一样的进程中，后端的任何故障不会致使Web Server挂掉。
• 专利：没有Apache mod_php之类的私有API的知识产权问题。
• 扩展：FastCGI后端和Web Server经过Socket进行通讯，二者能够分布式部署并方便进行横向扩展。

因此FastCGI一推出就几乎得到了全部主流Web Server的支持，Apache、Lighttpd、IIS、Cherokee……

题主说的php-fpm就是一种FastCGI的后端实现。

But，事情老是还有改进的余地的，FastCGI这套工做模式实际上没有什么太大缺陷，可是有些不安分的Python程序猿以为，FastCGI标准下写异步的Web服务仍是不太方便，若是可以收到请求后CGI端去处理，处理完毕后经过Callback回调来返回结果，那样岂不是很Coooool？！因此WSGI就被创造出来了：

WSGI（Web Server Gateway Interface）

Web服务器网关接口（Web Server Gateway Interface，缩写为WSGI）是为Python语言定义的Web服务器和Web应用程序或框架之间的一种简单而通用的接口。

当Web Server收到一个请求后，能够经过Socket把环境变量和一个Callback回调函数传给后端Web应用，Web应用在完成页面组装后经过Callback把内容返回给Web Server。这样作的优势有不少：

• 异步化，经过Callback将Web请求的工做拆解开，能够很方便的在一个线程空间里同时处理多个Web请求。
• 方便进行各类负载均衡和请求转发，不会形成后端Web应用阻塞。

1. Web开发有3P：Perl、Python、PHP。Perl是1987年发布的，Python是1989年，PHP是1995年。CGI标准提出的时候正是Perl如日中天的时候，因此CGI的提出当时也是主要为了解决Perl做为Web编程语言的需求。熟悉正则（regex）的程序员可能知道正则的事实标准叫作pcre（Perl兼容正则表达式，Perl Compatible Regular Expressions），这也从一个侧面体现了Perl做为一个古老的语言在当时对各类业界标准的影响。