Merge pull request #622 from rbike/syncoid-hold

syncoid hold

README.md

@@ -274,7 +274,7 @@ As of 1.4.18, syncoid also automatically supports and enables resume of interrup
 
 + --identifier=
 
-	Adds the given identifier to the snapshot name after "syncoid_" prefix and before the hostname. This enables the use case of reliable replication to multiple targets from the same host. The following chars are allowed: a-z, A-Z, 0-9, _, -, : and . .
+	Adds the given identifier to the snapshot and hold name after "syncoid_" prefix and before the hostname. This enables the use case of reliable replication to multiple targets from the same host. The following chars are allowed: a-z, A-Z, 0-9, _, -, : and . .
 
 + -r --recursive
 
@@ -316,6 +316,9 @@ As of 1.4.18, syncoid also automatically supports and enables resume of interrup
 
 	This argument tells syncoid to create a zfs bookmark for the newest snapshot after it got replicated successfully. The bookmark name will be equal to the snapshot name. Only works in combination with the --no-sync-snap option. This can be very useful for irregular replication where the last matching snapshot on the source was already deleted but the bookmark remains so a replication is still possible.
 
++ --use-hold
+	This argument tells syncoid to add a hold to the newest snapshot on the source and target after replication succeeds and to remove the hold after the next succesful replication. Setting a hold prevents the snapshots from being destroyed. The hold name incldues the identifier if set. This allows for separate holds in case of replication to multiple targets.
+
 + --preserve-recordsize
 
 	This argument tells syncoid to set the recordsize on the target before writing any data to it matching the one set on the replication src. This only applies to initial sends.

syncoid

@@ -24,7 +24,7 @@ my %args = ('sshconfig' => '', 'sshkey' => '', 'sshport' => '', 'sshcipher' => '
 GetOptions(\%args, "no-command-checks", "monitor-version", "compress=s", "dumpsnaps", "recursive|r", "sendoptions=s", "recvoptions=s",
                    "source-bwlimit=s", "target-bwlimit=s", "sshconfig=s", "sshkey=s", "sshport=i", "sshcipher|c=s", "sshoption|o=s@",
                    "debug", "quiet", "no-stream", "no-sync-snap", "no-resume", "exclude=s@", "skip-parent", "identifier=s",
-                   "no-clone-handling", "no-privilege-elevation", "force-delete", "no-rollback", "create-bookmark",
+                   "no-clone-handling", "no-privilege-elevation", "force-delete", "no-rollback", "create-bookmark", "use-hold",
                    "pv-options=s" => \$pvoptions, "keep-sync-snap", "preserve-recordsize", "mbuffer-size=s" => \$mbuffer_size,
                    "delete-target-snapshots")
                    or pod2usage(2);
@@ -362,6 +362,7 @@ sub syncdataset {
 	}
 
 	my $newsyncsnap;
+	my $matchingsnap;
 
 	# skip snapshot checking/creation in case of resumed receive
 	if (!defined($receivetoken)) {
@@ -609,7 +610,7 @@ sub syncdataset {
 		my $bookmark = 0;
 		my $bookmarkcreation = 0;
 
-		my $matchingsnap = getmatchingsnapshot($sourcefs, $targetfs, \%snaps);
+		$matchingsnap = getmatchingsnapshot($sourcefs, $targetfs, \%snaps);
 		if (! $matchingsnap) {
 			# no matching snapshots, check for bookmarks as fallback
 			my %bookmarks = getbookmarks($sourcehost,$sourcefs,$sourceisroot);
@@ -852,6 +853,42 @@ sub syncdataset {
 
 	$replicationCount++;
 
+	# if "--use-hold" parameter is used set hold on newsync snapshot and remove hold on matching snapshot both on source and target
+	# hold name: "syncoid" + identifier + hostname -> in case of replication to multiple targets separate holds can be set for each target by assinging different identifiers to each target. Only if all targets have been replicated all syncoid holds are removed from the matching snapshot and it can be removed
+	if (defined $args{'use-hold'}) {
+		my $holdcmd;
+		my $holdreleasecmd;
+		my $hostid = hostname();
+		my $matchingsnapescaped = escapeshellparam($matchingsnap);
+		my $holdname = "syncoid\_$identifier$hostid";
+		if ($sourcehost ne '') {
+			$holdcmd = "$sshcmd $sourcehost " . escapeshellparam("$sourcesudocmd $zfscmd hold $holdname $sourcefsescaped\@$newsyncsnapescaped");
+			$holdreleasecmd = "$sshcmd $sourcehost " . escapeshellparam("$sourcesudocmd $zfscmd release $holdname $sourcefsescaped\@$matchingsnapescaped");
+		} else {
+			$holdcmd = "$sourcesudocmd $zfscmd hold $holdname $sourcefsescaped\@$newsyncsnapescaped";
+			$holdreleasecmd = "$sourcesudocmd $zfscmd release $holdname $sourcefsescaped\@$matchingsnapescaped";
+		}
+		if ($debug) { print "DEBUG: Set new hold on source: $holdcmd\n"; }
+		system($holdcmd) == 0 or warn "WARNING: $holdcmd failed: $?";
+		# Do hold release only if matchingsnap exists
+		if ($matchingsnap) {
+			if ($debug) { print "DEBUG: Release old hold on source: $holdreleasecmd\n"; }
+			system($holdreleasecmd) == 0 or warn "WARNING: $holdreleasecmd failed: $?";
+		}
+		if ($targethost ne '') {
+			$holdcmd = "$sshcmd $targethost " . escapeshellparam("$targetsudocmd $zfscmd hold $holdname $targetfsescaped\@$newsyncsnapescaped");
+			$holdreleasecmd = "$sshcmd $targethost " . escapeshellparam("$targetsudocmd $zfscmd release $holdname $targetfsescaped\@$matchingsnapescaped");
+		} else {
+			$holdcmd = "$targetsudocmd $zfscmd hold $holdname $targetfsescaped\@$newsyncsnapescaped";				$holdreleasecmd = "$targetsudocmd $zfscmd release $holdname $targetfsescaped\@$matchingsnapescaped";
+		}
+		if ($debug) { print "DEBUG: Set new hold on target: $holdcmd\n"; }
+		system($holdcmd) == 0 or warn "WARNING: $holdcmd failed: $?";
+		# Do hold release only if matchingsnap exists
+		if ($matchingsnap) {
+			if ($debug) { print "DEBUG: Release old hold on target: $holdreleasecmd\n"; }
+			system($holdreleasecmd) == 0 or warn "WARNING: $holdreleasecmd failed: $?";
+		}
+	}
 	if (defined $args{'no-sync-snap'}) {
 		if (defined $args{'create-bookmark'}) {
 			my $bookmarkcmd;
@@ -2039,6 +2076,7 @@ Options:
   --no-sync-snap        Does not create new snapshot, only transfers existing
   --keep-sync-snap      Don't destroy created sync snapshots
   --create-bookmark     Creates a zfs bookmark for the newest snapshot on the source after replication succeeds (only works with --no-sync-snap)
+  --use-hold            Adds a hold to the newest snapshot on the source and target after replication succeeds and removes the hold after the next succesful replication. The hold name incldues the identifier if set. This allows for separate holds in case of multiple targets
   --preserve-recordsize Preserves the recordsize on initial sends to the target
   --no-rollback         Does not rollback snapshots on target (it probably requires a readonly target)
   --delete-target-snapshots With this argument snapshots which are missing on the source will be destroyed on the target. Use this if you only want to handle snapshots on the source.