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feat(syncoid): Sort snapshots by `createtxg` if possible 

It is possible for `creation` of a subsequent snapshot to be in the past
compared to the current snapshot due to system clock discrepancies,
which leads to earlier snapshots not being replicated in the initial
syncoid sync.

Also, `syncoid --no-sync-snap` might not pick up the most recently taken
snapshot if the clock moved backwards before taking that snapshot.

Sorting snapshots by the `createtxg` value is reliable and documented
in `man 8 zfsprops` as the proper way to order snapshots, but it was not
available in ZFS versions before 0.7.  To maintain backwards
compatibility, the sorting falls back to sorting by the `creation`
property, which was the old behavior.

Fixes: https://github.com/jimsalterjrs/sanoid/issues/815
This commit is contained in:
Nick Liu 2023-04-28 00:43:47 -05:00
parent 8fabaae5b8
commit 8907e0cb2f
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GPG Key ID: 1167C5F9C9897637
1 changed files with 14 additions and 6 deletions
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@ -862,9 +862,9 @@ sub syncdataset {
if (defined $args{'delete-target-snapshots'}) {
# Find the snapshots that exist on the target, filter with
# those that exist on the source. Remaining are the snapshots
# that are only on the target. Then sort by creation date, as
# to remove the oldest snapshots first.
my @to_delete = sort { $snaps{'target'}{$a}{'creation'}<=>$snaps{'target'}{$b}{'creation'} } grep {!exists $snaps{'source'}{$_}} keys %{ $snaps{'target'} };
# that are only on the target. Then sort to remove the oldest
# snapshots first.
my @to_delete = sort { sortsnapshots(\%snaps, $a, $b) } grep {!exists $snaps{'source'}{$_}} keys %{ $snaps{'target'} };
while (@to_delete) {
# Create batch of snapshots to remove
my $snaps = join ',', splice(@to_delete, 0, 50);
@ -1480,9 +1480,17 @@ sub readablebytes {
return $disp;
}
sub sortsnapshots {
my ($snaps, $left, $right) = @_;
if (defined $snaps->{'source'}{$left}{'createtxg'} && defined $snaps->{'source'}{$right}{'createtxg'}) {
return $snaps->{'source'}{$left}{'createtxg'} <=> $snaps->{'source'}{$right}{'createtxg'};
}
return $snaps->{'source'}{$left}{'creation'} <=> $snaps->{'source'}{$right}{'creation'};
}
sub getoldestsnapshot {
my $snaps = shift;
foreach my $snap ( sort { $snaps{'source'}{$a}{'creation'}<=>$snaps{'source'}{$b}{'creation'} } keys %{ $snaps{'source'} }) {
foreach my $snap (sort { sortsnapshots($snaps, $a, $b) } keys %{ $snaps{'source'} }) {
# return on first snap found - it's the oldest
return $snap;
}
@ -1496,7 +1504,7 @@ sub getoldestsnapshot {
sub getnewestsnapshot {
my $snaps = shift;
foreach my $snap ( sort { $snaps{'source'}{$b}{'creation'}<=>$snaps{'source'}{$a}{'creation'} } keys %{ $snaps{'source'} }) {
foreach my $snap (sort { sortsnapshots($snaps, $b, $a) } keys %{ $snaps{'source'} }) {
# return on first snap found - it's the newest
writelog('INFO', "NEWEST SNAPSHOT: $snap");
return $snap;
@ -1675,7 +1683,7 @@ sub pruneoldsyncsnaps {
sub getmatchingsnapshot {
my ($sourcefs, $targetfs, $snaps) = @_;
foreach my $snap ( sort { $snaps{'source'}{$b}{'creation'}<=>$snaps{'source'}{$a}{'creation'} } keys %{ $snaps{'source'} }) {
foreach my $snap ( sort { sortsnapshots($snaps, $b, $a) } keys %{ $snaps{'source'} }) {
if (defined $snaps{'target'}{$snap}) {
if ($snaps{'source'}{$snap}{'guid'} == $snaps{'target'}{$snap}{'guid'}) {
return $snap;