cancel jobs when it is known fresh device is already discovered

lib/App/Netdisco/Backend/Job.pm

@@ -22,6 +22,7 @@ foreach my $slot (qw/
       log
       device_key
       job_priority
+      is_cancelled
 
       _current_phase
       _last_namespace
@@ -45,6 +46,10 @@ sub BUILD {
     $job->action($1);
     $job->only_namespace($2);
   }
+
+  if (!defined $job->subaction) {
+    $job->subaction('');
+  }
 }
 
 =head1 METHODS
@@ -63,6 +68,19 @@ sub display_name {
     ($job->port || '');
 }
 
+=head2 cancel
+
+Log a status and prevent other stages from runnning.
+
+=cut
+
+sub cancel {
+  my ($job, $msg) = @_;
+  $msg ||= 'unknown reason for cancelled job';
+  $job->is_cancelled(true);
+  return Status->info($msg);
+}
+
 =head2 finalise_status
 
 Find the best status and log it into the job's C<status> and C<log> slots.

lib/App/Netdisco/Worker/Plugin.pm

@@ -36,6 +36,8 @@ register 'register_worker' => sub {
     debug sprintf '-> run worker %s/%s/%s',
       @$workerconf{qw/phase namespace priority/};
 
+    return if $job->is_cancelled;
+
     # check to see if this namespace has already passed at higher priority
     # and also update job's record of namespace and priority
     return $job->add_status( Status->info('skip: namespace passed at higher priority') )

lib/App/Netdisco/Worker/Plugin/Discover/CanonicalIP.pm

@@ -69,17 +69,25 @@ register_worker({ phase => 'main', driver => 'snmp' }, sub {
 
   return if $new_ip eq $old_ip;
 
-  schema('netdisco')->txn_do(sub {
-    # delete target device with the same vendor and serial number
-    schema('netdisco')->resultset('Device')->search({
+  return schema('netdisco')->txn_do(sub {
+    my $existing = schema('netdisco')->resultset('Device')->search({
       ip => $new_ip, vendor => $device->vendor, serial => $device->serial,
-    })->delete;
+    });
+
+    if (($job->subaction eq 'with-nodes') and $existing->count) {
+      $device->delete;
+      return $job->cancel(
+        " [$old_ip] device - cancelling fresh discover: already known as $new_ip");
+    }
+
+    # discover existing device but change IP, need to remove existing device
+    $existing->delete;
 
     # if target device exists then this will die
     $device->renumber($new_ip)
       or die "cannot renumber to: $new_ip"; # rollback
 
-    # is not done in renumber but required otherwise confusing at job end!
+    # is not done in renumber, but required, otherwise confusing at job end!
     schema('netdisco')->resultset('Admin')
       ->find({job => $job->id})->update({device => $new_ip}) if $job->id;
 

lib/App/Netdisco/Worker/Plugin/Discover/WithNodes.pm

@@ -13,8 +13,7 @@ register_worker({ phase => 'main' }, sub {
 
   # if requested, and the device has not yet been
   # arpniped/macsucked, queue those jobs now
-  return unless $device->in_storage
-    and $job->subaction and $job->subaction eq 'with-nodes';
+  return unless $device->in_storage and $job->subaction eq 'with-nodes';
 
   if (!defined $device->last_macsuck and $device->has_layer(2)) {
     jq_insert({