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FCGI::EV(3pm) User Contributed Perl Documentation FCGI::EV(3pm)


FCGI::EV - Implement FastCGI protocol for use in EV-based applications


This document describes FCGI::EV version v2.0.1


 use FCGI::EV;
 use Some::FCGI::EV::Handler;
 # while in EV::loop, accept incoming connection from web server into
 # $sock, then start handling FastCGI protocol on that connection,
 # using Some::FCGI::EV::Handler for processing CGI requests:
 FCGI::EV->new($sock, 'Some::FCGI::EV::Handler');
 # EXAMPLE: complete FastCGI server (without error handling code)
 #          use FCGI::EV::Std handler (download separately from CPAN)
 use Socket;
 use Fcntl;
 use EV;
 use FCGI::EV;
 use FCGI::EV::Std;
 my $path = '/tmp/fastcgi.sock';
 socket my $srvsock, AF_UNIX, SOCK_STREAM, 0;
 unlink $path;
 my $umask = umask 0;   # ensure 0777 perms for unix socket
 bind $srvsock, sockaddr_un($path);
 umask $umask;
 listen $srvsock, SOMAXCONN;
 fcntl $srvsock, F_SETFL, O_NONBLOCK;
 my $w = EV::io $srvsock, EV::READ, sub {
    accept my($sock), $srvsock;
    fcntl $sock, F_SETFL, O_NONBLOCK;
    FCGI::EV->new($sock, 'FCGI::EV::Std');


This module implement FastCGI protocol for use in EV-based applications. (That mean you have to run EV::loop in your application or this module will not work.)

It receive and parse data from web server, pack and send data to web server, but it doesn't process CGI requests received from web server - instead it delegate this work to another module called 'handler'. For one example of such handler, see FCGI::EV::Std.

FCGI::EV work using non-blocking sockets and initially was designed to use in event-based CGI applications (which able to handle multiple parallel CGI requests in single process without threads/fork). This require from CGI to avoid any operations which may block, like using SQL database - instead CGI should delegate all such tasks to remote services and talk to these services in non-blocking mode.

It also possible to use it to run usual applications. If you will do this using FCGI::EV::Std handler, then only one CGI request will be executed at a time (which is probably not what you expect from FastCGI!), because FCGI::EV::Std doesn't implement any process-manager. But it's possible to develop another handlers for FCGI::EV, which will support process-management and so will handle multiple CGI request in parallel.

This module doesn't require from user to use - any module for parsing CGI params can be used in general (details depends on used FCGI::EV handler module).



    FCGI::EV->new( $sock, $class );

Start talking FastCGI protocol on $sock (which should be socket open to just-connected web server), and use $class to handle received CGI requests.

Module $class should implement "FCGI::EV handler" interface. You can use either FCGI::EV::Std from CPAN or develop your own.

Return nothing. (Created FCGI::EV object will work in background and will be automatically destroyed after finishing I/O with web server.)


Handler class (which name provided in $class parameter to FCGI::EV->new()) must implement this interface:

When FCGI::EV object receive initial part of CGI request (environment variables) it will call $handler_class->new() to create handler object which should process that CGI request.

Parameter $server is FCGI::EV object itself. It's required to send CGI reply. WARNING! Handler may keep only weaken() reference to $server!

After calling new() FCGI::EV object ($server) will continue receiving STDIN content from web server and will call $handler->stdin() each time it get next part of STDIN.

The $data is next chunk of STDIN received from web server. Flag $is_eof will be true if $data was last part of STDIN.

Usually handler shouldn't begin processing CGI request until all content of STDIN will be received.

This method is optional. It will be called when connection to web server is closed and FCGI::EV object going to die (but it's still exists when DESTROY is called - except if DESTROY was called while global destruction stage).

Handler object may use DESTROY to interrupt current CGI request if web server close connection before CGI send it reply.


After handler got %env (in new()) and complete STDIN (in one or more calls of stdin()) it may start handling this CGI request and prepare reply to send to web server. To send this data it should use method $server->stdout(), where $server is object given to new() while creating handler object (it should keep weak reference to $server inside to be able to reply).

CGI may send reply in one or more parts. Last part should have $is_eof set to true. DESTROY method of handler object will be called shortly after handler object will do $server->stdout( $data, 1 ).


This handler will process CGI requests one-by-one (i.e. in blocking mode). On request function main::main() will be executed. That function may use standard module to get request parameters and send it reply using usual print to STDOUT.

There no error-handling code in this example, see FCGI::EV::Std for more details.

 package FCGI::EV::ExampleHandler;
 use Scalar::Util qw( weaken );
 use CGI::Stateless; # needed to re-init state between requests
 sub new {
    my ($class, $server, $env) = @_;
    my $self = bless {
        server  => $server,
        env     => $env,
        stdin   => q{},
    }, $class;
    return $self;
 sub stdin {
    my ($self, $stdin, $is_eof) = @_;
    $self->{stdin} .= $stdin;
    if ($is_eof) {
        local *STDIN;
        open STDIN, '<', \$self->{stdin};
        local %ENV = %{ $self->{env} };
        local $CGI::Q = CGI::Stateless->new();
        local *STDOUT;
        my $reply = q{};
        open STDOUT, '>', \$reply;
        $self->{server}->stdout($reply, 1);


There no errors returned in any way by this module, but there few warning messages may be printed:

"FCGI::EV: IO: %s"
While doing I/O with web server error %s happened and connection was closed.
"FCGI::EV: %s"
While parsing data from web server error %s happened and connection was closed. (That error probably mean bug either in web server or this module.)


Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker at <>. You will be notified automatically of any progress on your issue.

Source Code

This is open source software. The code repository is available for public review and contribution under the terms of the license. Feel free to fork the repository and submit pull requests.


    git clone



Alex Efros <>


This software is Copyright (c) 2009- by Alex Efros <>.

This is free software, licensed under:

  The MIT (X11) License
2018-04-14 perl v5.26.1