Merge pull request #189 from attie/nosync

added ability to skip datasets... simply set syncoid:no-sync=true

README.md

@@ -118,6 +118,32 @@ If ZFS supports resumeable send/receive streams on both the source and target th
 
 As of 1.4.18, syncoid also automatically supports and enables resume of interrupted replication when both source and target support this feature.
 
+##### Syncoid Dataset Properties
+
++ syncoid:sync
+
+  Available values:
+
+  + `true` (default if unset)
+
+    This dataset will be synchronised to all hosts.
+
+  + `false`
+
+    This dataset will not be synchronised to any hosts - it will be skipped. This can be useful for preventing certain datasets from being transferred when recursively handling a tree.
+
+  + `host1,host2,...`
+
+    A comma separated list of hosts. This dataset will only be synchronised by hosts listed in the property.
+
+    _Note_: this check is performed by the host running `syncoid`, thus the local hostname must be present for inclusion during a push operation // the remote hostname must be present for a pull.
+
+  _Note_: this will also prevent syncoid from handling the dataset if given explicitly on the command line.
+
+  _Note_: syncing a child of a no-sync dataset will currently result in a critical error.
+
+  _Note_: empty properties will be handled as if they were unset.
+
 ##### Syncoid Command Line Options
 
 + [source]

syncoid

@@ -184,6 +184,23 @@ sub syncdataset {
 
 	if ($debug) { print "DEBUG: syncing source $sourcefs to target $targetfs.\n"; }
 
+	my $sync = getzfsvalue($sourcehost,$sourcefs,$sourceisroot,'syncoid:sync');
+
+	if ($sync eq 'true' || $sync eq '-' || $sync eq '') {
+		# empty is handled the same as unset (aka: '-')
+		# definitely sync this dataset - if a host is called 'true' or '-', then you're special
+	} elsif ($sync eq 'false') {
+		if (!$quiet) { print "INFO: Skipping dataset (syncoid:sync=false): $sourcefs...\n"; }
+		return 0;
+	} else {
+		my $hostid = hostname();
+		my @hosts = split(/,/,$sync);
+		if (!(grep $hostid eq $_, @hosts)) {
+			if (!$quiet) { print "INFO: Skipping dataset (syncoid:sync doesn't include $hostid): $sourcefs...\n"; }
+			return 0;
+		}
+	}
+
 	# make sure target is not currently in receive.
 	if (iszfsbusy($targethost,$targetfs,$targetisroot)) {
 		warn "Cannot sync now: $targetfs is already target of a zfs receive process.\n";