FastCGI

FastCGI is a binary protocol for interfacing interactive programs with a web server. It is a variation on the earlier Common Gateway Interface (CGI). FastCGI's main aim is to reduce the overhead related to interfacing between web server and CGI programs, allowing a server to handle more web page requests per unit of time. Common Gateway Interface (CGI) is a protocol for interfacing external applications to web servers. CGI applications run in separate processes, which are created at the start of each request and torn down at the end. This "one new process per request" model makes CGI programs very simple to implement, but limits efficiency and scalability. At high loads, the operating system overhead for process creation and destruction becomes significant. Also, the CGI process model limits resource reuse methods, such as reusing database connections, in-memory caching, etc. To address the scalability shortcomings of CGI, Open Market developed FastCGI and first introduced it in their webserver product in the mid-1990s. Open Market originally developed FastCGI in part as a competitive response to Netscape's proprietary, in-process application programming interfaces (APIs) (Netscape Server Application Programming Interface (NSAPI)) for developing Web applications. While developed first by Open Market, FastCGI was then implemented by several other webserver makers. However, its approach competed against other methods to speed and simplify server-subprogram communication. Apache HTTP Server modules such as mod_perl and mod_php appeared around the same time, and gained popularity quickly. , all of these various methods, including CGI, remain in common use. Instead of creating a new process for each request, FastCGI uses persistent processes to handle a series of requests. These processes are owned by the FastCGI server, not the web server. To service an incoming request, the web server sends environment variable information and the page request to a FastCGI process over either a Unix domain socket, a named pipe, or a Transmission Control Protocol (TCP) connection.