NAME¶
"IO::Async::MergePoint" - resynchronise diverged control flow
SYNOPSIS¶
This module as now been moved to its own dist of Async::MergePoint.
It is kept here as a trivial subclass for backward compatibility. Eventually
this subclass may be removed. Any code using "IO::Async::MergePoint"
should instead use Async::MergePoint.
use Async::MergePoint;
my $merge = Async::MergePoint->new(
needs => [ "leaves", "water" ],
on_finished => sub {
my %items = @_;
# Make tea using $items{leaves} and $items{water}
}
);
Kettle->boil(
on_boiled => sub { $merge->done( "water", $_[0] ) }
);
Cupboard->get_tea_leaves(
on_fetched => sub { $merge->done( "leaves", $_[0] ) }
);
DESCRIPTION¶
Often in program logic, multiple different steps need to be taken that are
independent of each other, but their total result is needed before the next
step can be taken. In synchonous code, the usual approach is to do them
sequentially.
An "IO::Async"-based program could do this, but if each step involves
some IO idle time, better overall performance can often be gained by running
the steps in parallel. A Async::MergePoint object can then be used to wait for
all of the steps to complete, before passing the combined result of each step
on to the next stage.
A merge point maintains a set of outstanding operations it is waiting on; these
are arbitrary string values provided at the object's construction. Each time
the "done" method is called, the named item is marked as being
complete. When all of the required items are so marked, the
"on_finished" continuation is invoked.
When an item is marked as complete, a value can also be provided, which would
contain the results of that step. The "on_finished" callback is
passed a hash (in list form, rather than by reference) of the collected item
values.
AUTHOR¶
Paul Evans <leonerd@leonerd.org.uk>