Perl

Monitor and Cancel a Running DKIM Operation

Demonstrates the Chilkat Dkim.HeartbeatMs and Dkim.AbortCurrent properties, which monitor and cancel a long-running operation such as a DNS public-key lookup. HeartbeatMs sets how often an AbortCheck event fires, and AbortCurrent requests cancellation.

Background: Most Dkim work is instant, but anything touching DNS can stall on a slow or unresponsive server. HeartbeatMs makes the object emit a periodic AbortCheck callback during such calls so an application stays responsive and can show progress, and AbortCurrent — set from that callback or from another thread — breaks a blocked synchronous call out early. Together they turn an otherwise uninterruptible operation into a cancellable one.

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Chilkat2 Perl

use strict;
use warnings;
use Chilkat2;

# Demonstrates the Dkim properties HeartbeatMs and AbortCurrent, which monitor and cancel a
# long-running operation such as a DNS public-key lookup.

my $dkim = Chilkat2::Dkim->new;

# Fire an AbortCheck event callback every 100 ms during method calls.  In programming languages
# where Chilkat supports event callbacks, the callback can request cancellation.
$dkim->HeartbeatMs(100);

# AbortCurrent may be set to 1 to request cancellation of a running operation.  It is
# typically set from another thread, or from within an AbortCheck callback.  Setting it 0
# here ensures the operation is not pre-emptively aborted.
$dkim->AbortCurrent(0);

# PrefetchPublicKey performs a synchronous DNS lookup, which HeartbeatMs monitors and
# AbortCurrent can cancel.
my $success = $dkim->PrefetchPublicKey('myselector', 'example.com');
if (!$success) {
    print $dkim->LastErrorText, "\n";
    exit;
}

print "Public key prefetched.\n";