Daisuke Maki
and 2 contributors


AnyEvent::FIFO - Simple FIFO Callback Dispatch


    my $fifo = AnyEvent::FIFO->new(
        max_active => 1, # max "concurrent" callbacks to execute per slot

    # send to the "default" slot
    $fifo->push( \&callback, @args );

    # send to the "slot" slot
    $fifo->push( "slot", \&callback, @args );

    # dispatch is done automatically
    # wait for all tasks to complete

    sub callback {
        my ($guard, @args) = @_;

        # next callback will be executed when $guard is undef'ed or
        # when it goes out of scope


AnyEvent::FIFO is a simple FIFO queue to dispatch events in order.

If you use regular watchers and register callbacks from various places in your program, you're not necessarily guaranteed that the callbacks will be executed in the order that you expect. By using this module, you can register callbacks and they will be executed in that particular order.



max_active => $number

Number of concurrent callbacks to be executed per slot.

cv => $cv

Instance of AnyEvent condvar. AnyEvent::FIFO will create one for you if this is not provided.

AnyEvent::FIFO calls $cv->begin() when new task is pushed and $cv->end() when task is completed.

push ([$slot,] $cb [,@args])


The name of the slot that this callback should be registered to. If $slot is not specified, "__default__" is used.


The callback to be executed. Receives a "guard" object, and a list of arguments, as specied in @args.

$guard is the actually trigger that kicks the next callback to be executed, so you should keep it "alive" while you need it. For example, if you need to make an http request to declare the callback done, you should do something like this:

    $fifo->push( sub {
        my ($guard, @args) = @_;

        http_get $uri, sub {
            undef $guard; # *NOW* the callback is done
    } );

List of extra arguments that gets passed to the callback

active ([$slot])

Returns number of active tasks for a given slot.


The name of the slot, "__default__" is used if not specified.

waiting ([$slot])

Returns number of waiting tasks for a given slot.


The name of the slot, "__default__" is used if not specified.

cv ([$cv])

Gets or sets AnyEvent condvar.


A new condvar to assign to this FIFO


Attemps to drain the queue, if possible. You DO NOT need to call this method by yourself. It's handled automatically


Daisuke Maki.

This module is basically a generalisation of the FIFO queue used in AnyEvent::HTTP by Marc Lehmann.


The ZMQ::LibZMQ2 module is

Copyright (C) 2010 by Daisuke Maki

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.0 or, at your option, any later version of Perl 5 you may have available.