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Fix message for sending snapshots from ... about explicitly disable…
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…d datasets, and further in-vivo research (#623)

* lib/ZnapZend.pm: createSnapshot(): be pedantic about "implicit value of org.znapzend:enabled" for sub-datasets

* lib/ZnapZend.pm: createSnapshot(): update comments about creation and cleanup of snapshots on enabled=off sub-datasets

* lib/ZnapZend.pm: refactor listDisabledSourceDescendants() out of createSnapshot() so it can also be used in sendRecvCleanup()

* lib/ZnapZend.pm: refactor listDisabledSourceDescendants() calls to be done in refreshBackupPlans() once

Track the list of names as @{$backupSet->{srcDisabledDescendants}}
---------

Signed-off-by: Jim Klimov <[email protected]>
Co-authored-by: Tobias Oetiker <[email protected]>
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@jimklimov @oetiker
jimklimov and oetiker authored Feb 7, 2024
1 parent 85da5a3 commit 62394b2
Showing 1 changed file with 84 additions and 38 deletions.
122 changes: 84 additions & 38 deletions lib/ZnapZend.pm
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Original file line number Diff line number Diff line change
Expand Up @@ -145,6 +145,58 @@ my $killThemAll = sub {
exit 0;
};

# Return an array of dataset names which are local descendants of the
# provided $backupSet->{src} and have an explicit org.znapzend:enabled=off
# (note that currently each disabled descendant must be explicit - maybe
# an also-explicit recursion handling is a good idea for the future).
# The array may be empty if not in recursive mode, or no descendants
# exist, or none are disabled.
my $listDisabledSourceDescendants = sub {
my $self = shift;
my $backupSet = shift;

#no HUP handler in child
$SIG{HUP} = 'IGNORE';

my @dataSetsExplicitlyDisabled = ();
if ($backupSet->{recursive} eq 'on') {
$self->zLog->info("checking for explicitly excluded ZFS dependent datasets under '$backupSet->{src}'");

# restrict the list to the datasets that are descendant from the current
###my @dataSetList = grep /^$backupSet->{src}($|\/)/, @{$self->zZfs->listDataSets()};
my @dataSetList = @{$self->zZfs->listDataSets(undef, $backupSet->{src}, 1)};

if ( @dataSetList ) {
# the default sub-dataset enablement value is implicitly "on"
# (technically, the value inherited from $backupSet which we
# are currently processing, because it is enabled)
my $enabled_default = 'on';
if (defined($backupSet->{enabled})) {
$enabled_default = $backupSet->{enabled};
}

# for each sub-dataset: if the property "enabled" is set to "off", set the
# newly created snapshot for removal
for my $dataSet (@dataSetList){
# get the value for org.znapzend property
my @cmd = (@{$self->zZfs->priv}, qw(zfs get -H -s local -o value org.znapzend:enabled), $dataSet);
print STDERR '# ' . join(' ', @cmd) . "\n" if $self->debug;
open my $prop, '-|', @cmd;

# if the property does not exist, the command will just return.
# In this case, use the default determined above.
$prop = <$prop> || $enabled_default;
chomp($prop);
if ( $prop eq 'off' ) {
push(@dataSetsExplicitlyDisabled, $dataSet);
}
}
}
}

return \@dataSetsExplicitlyDisabled;
};

my $refreshBackupPlans = sub {
my $self = shift;
my $recurse = shift;
Expand All @@ -160,6 +212,13 @@ my $refreshBackupPlans = sub {
or die "No backup set defined or enabled, yet. run 'znapzendzetup' to setup znapzend\n";

for my $backupSet (@{$self->backupSets}){
$backupSet->{srcDisabledDescendants} = $self->$listDisabledSourceDescendants($backupSet);
if ($self->debug) {
for my $ds (@{$backupSet->{srcDisabledDescendants}}) {
$self->zLog->info('Found disabled sub-dataset: ' . $ds);
}
}

$backupSet->{srcPlanHash} = $self->zTime->backupPlanToHash($backupSet->{src_plan});
#check destination for remote pre-command
for (keys %$backupSet){
Expand Down Expand Up @@ -301,6 +360,11 @@ my $sendRecvCleanup = sub {
my $srcSubDataSets = $backupSet->{recursive} eq 'on'
? $self->zZfs->listSubDataSets($backupSet->{src}) : [ $backupSet->{src} ];

my @dataSetsExplicitlyDisabled = ();
if (defined($backupSet->{srcDisabledDescendants})) {
@dataSetsExplicitlyDisabled = @{$backupSet->{srcDisabledDescendants}};
}

#loop through all destinations
for my $dst (sort grep { /^dst_[^_]+$/ } keys %$backupSet){
my ($key) = $dst =~ /dst_([^_]+)$/;
Expand Down Expand Up @@ -379,7 +443,7 @@ my $sendRecvCleanup = sub {
my $dstDataSet = $srcDataSet;
$dstDataSet =~ s/^\Q$backupSet->{src}\E/$backupSet->{$dst}/;

$self->zLog->debug('sending snapshots from ' . $srcDataSet . ' to ' . $dstDataSet);
$self->zLog->debug('sending snapshots from ' . $srcDataSet . ' to ' . $dstDataSet . ((grep (/^\Q$srcDataSet\E$/, @dataSetsExplicitlyDisabled)) ? ": not enabled, should be skipped" : ""));
{
local $@;
eval {
Expand Down Expand Up @@ -1044,46 +1108,28 @@ my $createSnapshot = sub {
}
}

# Remove snapshots from descendant subsystems that have the property
# "enabled" set to "off", if the "recursive" flag is set to "on",
# so their newly created snapshots are discarded quickly and disk
# space is not abused by something we do not back up subsequently.
# First we snapshot the backupSet recursively and atomically, but
# later we would remove snapshots from descendant subsystems that
# have the property "enabled" set to "off", if the "recursive" flag
# is set to "on", so their newly created snapshots are discarded
# quickly and disk space is not abused by something we do not back
# up subsequently (it might still become blocked if znapzend crashes
# or the host reboots between such snapshot creation and clean-up).
# This only applies if we made a single-command recursive snapshot.
if ($backupSet->{recursive} eq 'on') {

$self->zLog->info("checking for explicitly excluded ZFS dependent datasets under '$backupSet->{src}'");

# restrict the list to the datasets that are descendant from the current
###my @dataSetList = grep /^$backupSet->{src}($|\/)/, @{$self->zZfs->listDataSets()};
my @dataSetList = @{$self->zZfs->listDataSets(undef, $backupSet->{src}, 1)};
if ( @dataSetList ) {

# for each dataset: if the property "enabled" is set to "off", set the
# newly created snapshot for removal
my @dataSetsExplicitlyDisabled = ();
for my $dataSet (@dataSetList){

# get the value for org.znapzend property
my @cmd = (@{$self->zZfs->priv}, qw(zfs get -H -s local -o value org.znapzend:enabled), $dataSet);
print STDERR '# ' . join(' ', @cmd) . "\n" if $self->debug;
open my $prop, '-|', @cmd;

# if the property does not exist, the command will just return. In this case,
# the value is implicit "on"
$prop = <$prop> || "on";
chomp($prop);
if ( $prop eq 'off' ) {
push(@dataSetsExplicitlyDisabled, $dataSet . '@' . $snapshotSuffix);
}
}
my @dataSetsExplicitlyDisabled = ();
if (defined($backupSet->{srcDisabledDescendants})) {
@dataSetsExplicitlyDisabled = @{$backupSet->{srcDisabledDescendants}};
}

# remove the snapshots previously marked
# removal here is non-recursive to allow for fine-grained control
if ( @dataSetsExplicitlyDisabled ){
$self->zLog->info("Requesting removal of marked datasets: ". join( ", ", @dataSetsExplicitlyDisabled));
$self->zZfs->destroySnapshots(\@dataSetsExplicitlyDisabled, 0);
}
# Remove the snapshots previously marked (if any). Note that the
# removal here is non-recursive to allow for fine-grained control:
if (@dataSetsExplicitlyDisabled) {
my @snapshotsToRemove = ();
for my $dataSet (@dataSetsExplicitlyDisabled) {
push (@snapshotsToRemove, $dataSet . '@' . $snapshotSuffix);
}
$self->zLog->info("Requesting removal of marked snapshots from \"disabled\" datasets: ". join( ", ", @snapshotsToRemove));
$self->zZfs->destroySnapshots(\@snapshotsToRemove, 0);
}

#clean up env variables
Expand Down

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