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Anonymous, 2008-09-07 22:35


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#!rst
=====================
the FastCGI Interface
=====================

-------------------
Module: mod_fastcgi
-------------------

.. meta::
  :keywords: lighttpd, FastCGI

.. contents:: Table of Contents

Description
===========

lighttpd provides an interface to external programs that 
support the FastCGI interface. The FastCGI Interface is 
defined by http://www.fastcgi.com/ and is a 
platform-independent and server-independent interface between
a web-application and a webserver.

This means that FastCGI programs that run with the Apache 
webserver will run seamlessly with lighttpd and vice versa.

FastCGI
-------

**Warning:** As of php 5.2.3, the cgi binary is installed as "/usr/local/bin/php-cgi" by default, instead of "/usr/local/bin/php". Make sure to substitute the relevant parts in the documentation below.

FastCGI removes a lot of the limitations of CGI programs. 
CGI programs have the problem that they have to be restarted 
by the webserver for every request which leads to really bad 
performance values.

FastCGI removes this limitation by keeping the process running 
and handling the requests by this always running process. This 
removes the time used for the fork() and the overall startup 
and cleanup time which is necessary to create and destroy a 
process.

While CGI programs communicate to the server over pipes, 
FastCGI processes use Unix-Domain-Sockets or TCP/IP to talk 
with the webserver. This gives you the second advantage over 
simple CGI programs: FastCGI don't have to run on the webserver
itself but anywhere in the network. 

lighttpd takes it a little bit further by providing an internal 
FastCGI load-balancer which can be used to balance the load 
over multiple FastCGI Servers. In contrast to other solutions 
only the FastCGI process has to be on the cluster and not the 
whole webserver. That gives the FastCGI process more resources
than a e.g. *load-balancer+apache+mod_php* solution.

If you compare FastCGI against an *apache+mod_php* setup you 
should note that FastCGI provides additional security as the 
FastCGI process can be run under different permissions than 
the webserver and can also live in a chroot which might be 
different than the one the webserver is running in. 

Options
=======

lighttpd provides the FastCGI support via the fastcgi-module 
(mod_fastcgi) which provides 3 options in the config-file:

* fastcgi.debug: a value between 0 and 65535 to set the debug-level in the FastCGI module. Currently only 0 and 1 are used. Use 1 to enable some debug output, 0 to disable it.

Example: ::

    fastcgi.debug = 1

* fastcgi.map-extensions: map multiple extensions to the same fastcgi server

  Example: ::

    fastcgi.map-extensions = ( ".php3" => ".php" )

* fastcgi.server: tell the module where to send FastCGI requests to. Every file-extension can have it own handler. Load-Balancing is done by specifying multiple handlers for the same extension.

  structure of fastcgi.server section: ::

    ( <extension> => 
      (  
        ( "host" => <string> ,
          "port" => <integer> ,
      "socket" => <string>,                 # either socket or host+port
      "bin-path" => <string>,               # optional 
      "bin-environment" => <array>,         # optional 
      "bin-copy-environment" => <array>,    # optional 
          "mode" => <string>,                   # optional
          "docroot" => <string> ,               # optional if "mode" is not "authorizer" 
          "check-local" => <string>,            # optional
      "max-procs" => <integer>,             # optional - when omitted, default is 4
      "broken-scriptfilename" => <boolean>, # optional
          "disable-time" => <integer>,          # optional
          "allow-x-send-file" => <boolean>,     # optional
          "kill-signal" => <integer>,           # optional (v1.4.14+ though option is accepted in earlier versions)
    ),
        ( "host" => ... 
        ) 
      )
    )

* <extension>: is the file-extension or prefix (if started with "/")
* "host":      is hostname/ip of the FastCGI process
* "port":      is tcp-port on the "host" used by the FastCGI process
* "bin-path":  path to the local FastCGI binary which should be started if no local FastCGI is running
* "socket":    path to the unix-domain socket
* "mode":      is the FastCGI protocol mode. Default is "responder", also "authorizer" mode is implemented.
* "docroot":   is optional and is the docroot on the remote host for default "responder" mode. For "authorizer" mode it is MANDATORY and it points to docroot for authorized requests. For security reasons it is recommended to keep this docroot outside of server.document-root tree.
* "check-local": is optional and may be "enable" (default) or "disable". If enabled the server first checks for a file in local *server.document-root* tree and returns 404 (Not Found) if no such file, and does not fall back to FastCGI. If disabled, the server forwards a request to the FastCGI interface without this check.
* "broken-scriptfilename": breaks *SCRIPT_FILENAME* in a way that PHP can extract *PATH_INFO* from it (default: disabled)
* "disable-time": time to wait before a disabled backend is checked again
* "allow-x-send-file": controls if *X-LIGHTTPD-send-file* and *X-Sendfile* headers are allowed 

  If bin-path is set:

* "max-procs": the number of fastcgi processes that will be started
* "bin-environment": put an entry into the environment of the started process
* "bin-copy-environment": clean up the environment and copy only the specified entries into the fresh environment of the spawn process

  New in 1.4.14:
* "kill-signal": By default lighttpd send *SIGTERM(15)* to FastCGI processes, which were spawned by lighttpd. Applications, which link libfcgi_, need to be killed with *SIGUSR1(10)*. This applies to php <5.2.1, lua-magnet_ and others. Option is accepted in prior versions, option is functional in 1.4.14+.

Examples
--------

  Multiple extensions for the same host: ::

    fastcgi.server = ( ".php" =>
      (( "host" => "127.0.0.1", 
         "port" => 1026,
     "bin-path" => "/usr/local/bin/php" 
      )),
      ".php4" =>
      (( "host" => "127.0.0.1",
     "port" => 1026
      ))
    )

  Example with prefix: ::

    fastcgi.server = ( "/remote_scripts/" =>
      (( "host" => "192.168.0.3",
     "port" => 9000,
         "check-local" => "disable",
         "docroot" => "/" # remote server may use 
                      # it's own docroot
      ))
    )

  The request "http://my.example.org/remote_scripts/test.cgi" will
  be forwarded to fastcgi server at "192.168.0.3" and the value
  "/remote_scripts/test.cgi" will be used for the *SCRIPT_NAME*
  variable. Remote server may prepend it with its own 
  document root. The handling of index files is also the 
  responsibility of remote server for this case.

  In the case that the prefix is not terminated with a slash, 
  the prefix will be handled as file and "/test.cgi" would become
  a *PATH_INFO* instead of part of *SCRIPT_NAME*.

  Example for "authorizer" mode: ::

    fastcgi.server = ( "/remote_scripts/" =>
      (( "host" => "10.0.0.2",
     "port" => 9000,
         "docroot" => "/path_to_private_docs",
         "mode" => "authorizer" 
      ))
    )

  Note that if "docroot" is specified then its value will be 
  used in *DOCUMENT_ROOT* and *SCRIPT_FILENAME* variables passed
  to FastCGI server.

Load-Balancing
==============

The FastCGI plugin provides automatically a load-balancing between 
multiple FastCGI servers. ::

  fastcgi.server = ( ".php" => 
     (( "host" => "10.0.0.2", "port" => 1030 ),
      ( "host" => "10.0.0.3", "port" => 1030 ))
    )

To understand how the load-balancing works you can enable the 
*fastcgi.debug* option and will get a similar output as here: ::

  proc: 127.0.0.1 1031  1 1 1 31454
  proc: 127.0.0.1 1028  1 1 1 31442
  proc: 127.0.0.1 1030  1 1 1 31449
  proc: 127.0.0.1 1029  1 1 2 31447
  proc: 127.0.0.1 1026  1 1 2 31438
  got proc: 34 31454
  release proc: 40 31438
  proc: 127.0.0.1 1026  1 1 1 31438
  proc: 127.0.0.1 1028  1 1 1 31442
  proc: 127.0.0.1 1030  1 1 1 31449
  proc: 127.0.0.1 1031  1 1 2 31454
  proc: 127.0.0.1 1029  1 1 2 31447

Even if this for multiple FastCGI children on the local machine 
the following explanation is valid for remote connections too.

The output shows: 

- IP, port, unix-socket (is empty here)
- is-local, state (0 - unset, 1 - running, ... )
- active connections (load)
- PID

As you can see the list is always sorted by the load field. 

Whenever a new connection is requested, the first entry (the one 
with the lowest load) is selected, the load is increased (got proc: ...) 
and the list is sorted again.

If a FastCGI request is done or the connection is dropped, the load on the 
FastCGI proc decreases and the list is sorted again (release proc: ...)

This behaviour is very light-weight in code and still very efficient 
as it keeps the fastcgi-servers equally loaded even if they have different 
CPUs. 

FastCGI and Programming Languages
=================================        

Preparing PHP as a FastCGI program
----------------------------------

One of the most important application that has a FastCGI 
interface is php which can be downloaded from 
http://www.php.net/ . You have to recompile the php from 
source to enable the FastCGI interface as it is normally 
not enabled by default in the distributions.

If you already have a working installation of PHP on a 
webserver execute a small script which just contains ::

  <?php phpinfo(); ?>

and search for the line in that contains the configure call. 
You can use it as the base for the compilation. 

You have to remove all occurrences of `--with-apxs`, `--with-apxs2` 
and the like which would build PHP with Apache support.  Add the
next three switches to compile PHP with FastCGI support::

  $ ./configure \
    --enable-fastcgi \
    --enable-force-cgi-redirect \
    ...

After compilation and installation check that your PHP 
binary contains FastCGI support by calling: ::

  $ php -v
  PHP 4.3.3RC2-dev (cgi-fcgi) (built: Oct 19 2003 23:19:17)

The important part is the (cgi-fcgi).

Starting a FastCGI-PHP
----------------------

Starting with version 1.3.6 lighttpd can spawn the FastCGI 
processes locally itself if necessary: ::

  fastcgi.server = ( ".php" =>
    (( "socket" => "/tmp/php-fastcgi.socket",
       "bin-path" => "/usr/local/bin/php" 
    ))
  )

PHP provides 2 special environment variables which control the number of
spawned workers under the control of a single watching process
(PHP_FCGI_CHILDREN) and the number of requests what a single worker
handles before it kills itself. ::

  fastcgi.server = ( ".php" =>
     (( "socket" => "/tmp/php-fastcgi.socket",
        "bin-path" => "/usr/local/bin/php",
        "bin-environment" => ( 
          "PHP_FCGI_CHILDREN" => "16",
          "PHP_FCGI_MAX_REQUESTS" => "10000" 
        )
     ))
   )

To increase the security of the started process you should only pass 
the necessary environment variables to the FastCGI process. ::

  fastcgi.server = ( ".php" =>
     (( "socket" => "/tmp/php-fastcgi.socket",
        "bin-path" => "/usr/local/bin/php",
        "bin-environment" => ( 
           "PHP_FCGI_CHILDREN" => "16",
           "PHP_FCGI_MAX_REQUESTS" => "10000" ),
        "bin-copy-environment" => (
       "PATH", "SHELL", "USER" )
     ))
   )

Configuring PHP
---------------

If you want to use PATH_INFO and PHP_SELF in you PHP scripts you have to
configure php and lighttpd. The php.ini needs the option: ::

  cgi.fix_pathinfo = 1

and the option "broken-scriptfilename" in your fastcgi.server config: ::

  fastcgi.server = ( ".php" =>
     (( "socket" => "/tmp/php-fastcgi.socket",
        "bin-path" => "/usr/local/bin/php",
        "bin-environment" => ( 
          "PHP_FCGI_CHILDREN" => "16",
          "PHP_FCGI_MAX_REQUESTS" => "10000" ),
        "bin-copy-environment" => (
          "PATH", "SHELL", "USER" ),
        "broken-scriptfilename" => "enable" 
     ))
   )

Why this ? the "cgi.fix_pathinfo = 0" would give you a working *PATH_INFO* 
but no *PHP_SELF*. If you enable it, it turns around. To fix the
*PATH_INFO* `--enable-discard-path` needs a *SCRIPT_FILENAME* which is against the CGI spec, a
broken-scriptfilename. With "cgi.fix_pathinfo = 1" in php.ini and
"broken-scriptfilename => "enable"" you get both.

Please note that the CGI binary has been renamed to php-cgi in 5.2.3, so you'll probably have a path like /usr/local/bin/php-cgi in your config.

Roadsend PHP -- The Other PHP
-----------------------------

Roadsend PHP, freely available from http://code.roadsend.com/pcc, is an alternative implementation of PHP that works with lighttpd. It can run PHP code directly (as Zend PHP does), but it can also compile PHP code directly to native FastCGI binaries.

An example configuration that can be used for interpreting .php files on your server with Roadsend PHP: ::

     fastcgi.server = ( ".php" =>
                         ( "localhost" =>
                             (
                               "host"        =>     "127.0.0.1",
                               "port"        =>     1026,
                               "bin-path"    =>     "/opt/roadsend/pcc/modules/fastcgi/pcc.fcgi",
                             )
                         )
                      )

To deploy a compiled application, you will need mod_rewrite enabled in your lighttpd server. Assuming your app is named "myapp", copy the compiled app "myapp.fcgi" and associated library "libmyapp_u.so" created by pcc to your cgi-bin directory:

     cp myapp.fcgi libmyapp_u.so /usr/lib/cgi-bin/

We use the mod_rewrite module to grab all requests for PHP files in the application's web root directory and re-route them to the FastCGI binary. We also allow for an index.php file ::

     # serve index pages
     url.rewrite-once = ( "^/myapp/$" => "/myapp/index.php" )

     # main fastcgi entry
     $HTTP["url"] =~ "^/myapp/.+\.php$" {

             fastcgi.server = (
                      "/myapp" =>
                                  ( "localhost" =>
                                             ( "bin-path" => "/var/www/localhost/cgi-bin/myapp.fcgi",
                                                "docroot" => "/var/www/localhost/htdocs/myapp",
                                                "host"               =>              "127.0.0.1",
                                                "port"               =>              1026,
                                                "check-local" => "disable" 
                                             )
                                     )
                             )

     } # HTTP[url]

External Spawning
-----------------

Spawning FastCGI processes directly in the webserver has some 
disadvantages like

- FastCGI process can only run locally
- has the same permissions as the webserver
- has the same base-dir as the webserver

As soon as you are using a separate FastCGI Server to
take off some load from the webserver you have to control
the FastCGI process by a external program like "spawn-fcgi".

"spawn-fcgi" is used to start a FastCGI process in its own
environment and set the user-id, group-id and change to 
another root-directory (chroot).

For convenience a wrapper script should be used which takes 
care of all the necessary option. Such a script in included 
in the lighttpd distribution and is call spawn-php.sh.

The script has a set of config variables you should take 
a look at: ::

  ## ABSOLUTE path to the spawn-fcgi binary
  SPAWNFCGI="/usr/local/sbin/spawn-fcgi" 

  ## ABSOLUTE path to the PHP binary
  FCGIPROGRAM="/usr/local/bin/php" 

  ## bind to tcp-port on localhost
  FCGIPORT="1026" 

  ## bind to unix domain socket
  # FCGISOCKET="/tmp/php.sock" 
  ## number of PHP childs to spawn
  PHP_FCGI_CHILDREN=10

  ## number of request server by a single php-process until
  ## is will be restarted
  PHP_FCGI_MAX_REQUESTS=1000

  ## IP adresses where PHP should access server connections
  ## from
  FCGI_WEB_SERVER_ADDRS="127.0.0.1,192.168.0.1" 

  # allowed environment variables separated by spaces
  ALLOWED_ENV="ORACLE_HOME PATH USER" 

  ## if this script is run as root switch to the following user
  USERID=wwwrun
  GROUPID=wwwrun

If you have set the variables to values that fit to your 
setup you can start it by calling: ::

  $ spawn-php.sh
  spawn-fcgi.c.136: child spawned successfully: PID: 6925

If you get "child spawned successfully: PID:" the php 
processes could be started successfully. You should see them 
in your process list: ::

  $ ps ax | grep php
  6925 ?        S      0:00 /usr/local/bin/php
  6928 ?        S      0:00 /usr/local/bin/php
  ...

The number of processes should be *PHP_FCGI_CHILDREN* + 1. 
Here the process 6925 is the master of the slaves which 
handle the work in parallel. Number of parallel workers can 
be set by *PHP_FCGI_CHILDREN*. A worker dies automaticly of 
handling *PHP_FCGI_MAX_REQUESTS* requests as PHP might have 
memory leaks.

If you start the script as user root php processes will be 
running as the user *USERID* and group *GROUPID* to drop the 
root permissions. Otherwise the php processes will run as 
the user you started script as.

As the script might be started from a unknown stage or even 
directly from the command-line it cleans the environment 
before starting the processes. *ALLOWED_ENV* contains all 
the external environement variables that should be available 
to the php-process.

A patch for "spawn-fcgi" so that it can accept a custom configuration file location can be found here:

http://forum.lighttpd.net/topic/446#1294

The patch must be applied in the source directory of lighttpd's source code. The file to patch is "spawn-fcgi.c" and requires a recompile of lighty to have the binary compiled with it as well.

It is required to add the following in the "spawn-php.sh" file: ::

  ## ABSOLUTE path to PHP config
  FCGI_CONFIG="/path/to/php/config/php5.ini" 

After: ::

  ## ABSOLUTE path to the PHP binary
  FCGIPROGRAM="/etc/lighttpd/php" 

And change the similar lines at the bottom of the file to: ::

  if test x$UID = x0; then
    EX="$SPAWNFCGI -p $FCGIPORT -f $FCGIPROGRAM -u $USERID -g $GROUPID -C $PHP_FCGI_CHILDREN -x $FCGI_CONFIG" 
  else
    EX="$SPAWNFCGI -p $FCGIPORT -f $FCGIPROGRAM -C $PHP_FCGI_CHILDREN -x $FCGI_CONFIG" 
  fi

Perl
----

For Perl you have to install the FCGI module from CPAN.

Skeleton for remote authorizer
==============================

The basic functionality of authorizer is as follows (see
http://www.fastcgi.com/devkit/doc/fcgi-spec.html, 6.3 for 
details). ::

  #include <fcgi_stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  int main () {
    char* p;

    while (FCGI_Accept() >= 0) {   
      /* wait for fastcgi authorizer request */

      printf("Content-type: text/html\r\n");

      if ((p = getenv("QUERY_STRING")) == NULL) ||
           <QUERY_STRING is unauthorized>)
           printf("Status: 403 Forbidden\r\n\r\n");

      else printf("\r\n");  
        /* default Status is 200 - allow access */
    }

    return 0;
  }

It is possible to use any other variables provided by 
FastCGI interface for authorization check. Here is only an 
example.

Troubleshooting
===============

fastcgi.debug should be enabled for troubleshooting.

If you get: ::

  (fcgi.c.274) connect delayed:  8
  (fcgi.c.289) connect succeeded:  8
  (fcgi.c.745) unexpected end-of-file (perhaps the fastcgi 
     process died):  8

the fastcgi process accepted the connection but closed it 
right away. This happens if *FCGI_WEB_SERVER_ADDRS* doesn't 
include the host where you are connection from.

If you get ::

  (fcgi.c.274) connect delayed:  7
  (fcgi.c.1107) error: unexpected close of fastcgi connection 
     for /peterp/seite1.php (no fastcgi process on host/port ?)
  (fcgi.c.1015) emergency exit: fastcgi: connection-fd: 5 
     fcgi-fd: 7

the fastcgi process is not running on the host/port you are 
connection to. Check your configuration.

If you get ::

  (fcgi.c.274) connect delayed:  7
  (fcgi.c.289) connect succeeded:  7

everything is fine. The connect() call just was delayed a 
little bit and is completely normal.

.. _libfcgi: http://www.fastcgi.com/
.. _lua-magnet: http://jan.kneschke.de/projects/lua

Some Python (perhaps Flup) information would be nice..
----

Could anyone provide information about C/C++

Updated by Anonymous about 12 years ago · 41 revisions