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=head2 CLASS->new(%opts)

Constructor. Normally L<Data::Consumer>'s constructor is not called
directly, instead the constructor of a subclass is used.  However to
make it easier to have a data driven load process  L<Data::Consumer>
accepts the C<type> argument which should specify the the short name of
the subclass (the part after C<Data::Consumer::>) or the full name of
the subclass.

Thus

    Data::Consumer->new(type=>'MySQL',%args);

is exactly equivalent to calling

    Data::Consumer::MySQL->new(%args);

except that the former will automatically require or use the appropriate module 
and the latter necessitates that you do so yourself.

Every L<Data::Consumer> subclass constructor supports the following
arguments on top of any that are subclass specific. Additionally some
arguments are universally used, but have different meaning depending on
the subclass. 

=over 4

=item unprocessed

How to tell if the item is unprocessed. 

How this argument is interpreted depends on the L<Data::Consumer>
subclass involved.

=item working

How to tell if the item is currently being worked on.

How this argument is interpreted depends on the L<Data::Consumer>
subclass involved.

=item processed

How to tell if the item has already been worked on.

How this argument is interpreted depends on the L<Data::Consumer>
subclass involved.

=item failed

How to tell if processing failed while handling the item.

How this argument is interpreted depends on the L<Data::Consumer>
subclass involved.

=item max_passes => $num_or_undef

Normally C<consume()> will loop through the data set until it is
exhausted.  By setting this parameter you can control the maximum number
of iterations, for instance setting it to C<1> will result in a single
pass through the data per invocation. If C<0> (or any other false value)
is treated as meaning "loop until exhausted".

=item max_processed => $num_or_undef

Maximum number of items to process per invocation.

If set to a false value there is no limit.

=item max_failed => $num_or_undef

Maximum number of failed process attempts that may occur before consume will stop.
If set to a false value there is no limit. Setting this to 1 will cause processing
to stop after the first failure.

=item max_elapsed => $seconds_or_undef

Maximum amount of time that may have elapsed when starting a new
process. If more than this value has elapsed then no further processing
occurs. If C<0> (or any false value) then there is no time limit.

=item proceed => $code_ref

This is a callback that may be used to control the looping process in
consume via the C<proceed()> method. See the documentation of
C<consume()> and C<proceed()>

=item sweep => $bool

*** NOTE CURRENTLY THIS OPTION IS DISABLED ***

If this parameter is true, and there are four modes defined
(C<unprocessed>, C<working>, C<processed>, C<failed>) then consume will
perform a "sweep up" after every pass, which is responsible for moving
"abandonded" files from the working directory (such as from a previous
process that segfaulted during processing). Generally this should
not be necessary.

=back


=head2 CLASS->register(@alias)

Used by subclasses to register themselves as a L<Data::Consumer>
subclass and register any additional aliases that the class may be
identified as.

Will throw an exception if any of the aliases are already associated to
a different class.

When called on a subclass in list context returns a list of the
subclasses registered aliases,

If called on L<Data::Consumer> in list context returns a list of all
alias class mappings.

=cut