Introduction to FastCGI

In the beginning

One app, one web server

apache.c:

    if (page == "/loginform.html") {
        sendfile("templates/loginform.html");
    } else if (page == "/profile.html") {
        printf("Status: 200 OK\r\n");
        printf("Content-type: text/html\r\n");
        printf("\r\n");
        printf("<h1>Hello %s</h1>", user);

CGI

Generate responses with an external process

Web server does:

$ export REQUEST_URI="/loginform.asp"
$ ./mycgi.exe
Status: 200 OK
Content-Type: text/html

<h1>Please login</h1>
<form action="/dologin">
...

CGI

Requests are passed through envp and stdin

int main(int argc, char **argv, char **envp){
    int len = atoi(getenv("CONTENT_LENGTH"));
    char *req = malloc(len);

    read(STDIN_FILENO, len, req);

{'u','s','e','r','=','m','i','k','e','6','9','&'
 'p','a','s','s','=','t','h','r','i','l','l','7'}

CGI

HTTP GET query string

char *query = getenv("QUERY_STR");

Which page was requested?

char *uri = getenv("REQUEST_URI");

HTTP POST vars? File uploads?

fread(buf, count, 1, stdin);

CGI

Decouples web server from web app

No more embedded:

• mod_php
• mod_python
• mod_ruby
• mod_rack / phusion

CGI

Spawn a new process for each request?

$ export REQUEST_URI="/loginform.asp"
$ ./mycgi.exe
$ export REQUEST_URI="/login.asp"
$ ./mycgi.exe
$ export REQUEST_URI="/profile.asp"
$ ./mycgi.exe
$ export REQUEST_URI="/deleteprofile.asp"
$ ./mycgi.exe
$ export REQUEST_URI="/redirect.asp"
$ ./mycgi.exe

FastCGI

Advantages:

• Fast

FastCGI

Fast:

$ ./myfcgi.exe
    Listening on 127.0.0.1:1337

FastCGI

For each request, web server:

• Connects to fastcgi app
• Sends the request variables
• Reads the reply, forwards it to client

FastCGI

127.0.0.1:1337

or

/tmp/myapp.sock

or

192.168.1.{90,91,92}:1337

Terminal App

Terminal

Problems with FastCGI

Alternatives to FastCGI

SCGI - Simple Common Gateway Interface

WSGI - Web Server Gateway Interface

PSGI - Perl Server Gateway Interface

ISAPI - Internet Server Application Programming Interface

SCGI

Simple

SCGI

Simple protocol

New (2006)

Not widely used

WSGI

Web Server Gateway Interface

Made for Python

They don’t care about everyone else

PSGI

Perl Server Gateway Interface

Made for Perl

They don’t care about everyone else

ISAPI

Internet Server API

Made by Microsoft

They don’t care about everyone else

Uses DLLs and OS services, much tighter coupling

FastCGI Support

Every major webserver can forward requests over FastCGI

Every major language can respond to FastCGI requests

Q&A

Any questions?