Subversion Repositories zfs_utils

# Execute a command and return its output.

# If called in scalar context, returns the full output as a single string.

# If called in list context, returns the output split into lines.

# If $merge_stderr is true (default), stderr is merged into stdout (only for scalar commands).

# returns empty string or empty list on failure and logs failure message.

sub runCmd {

   my ($cmd, $merge_stderr) = @_;

   $merge_stderr = 1 unless defined $merge_stderr;

   my $output = '';

   if (ref $cmd eq 'ARRAY') {

      # Execute without a shell (safer). Note: stderr is not merged in this path.

      open my $fh, '-|', @{$cmd} or do {

         logMsg("runCmd: failed to exec '@{$cmd}': $!");

         return wantarray ? () : '';

      };

      local $/ = undef;

      $output = <$fh>;

      close $fh;

   } else {

      # Scalar command runs via the shell; optionally merge stderr into stdout.

      my $c = $cmd;

      $c .= ' 2>&1' if $merge_stderr;

      $output = `$c`;

   }

   $output //= '';

   if (wantarray) {

      return $output eq '' ? () : split(/\n/, $output);

   } else {

      return $output;

   }

}

sub makeReplicateCommands {

   my ($sourceSnapsRef, $statusRef, $newStatusRef) = @_;

   $sourceSnapsRef ||= [];

   $statusRef     ||= [];

   $newStatusRef  ||= [];

   # parse snapshots: each line is expected to have snapshot fullname as first token: pool/fs@snap ...

   my %snaps_by_fs;

   foreach my $line (@$sourceSnapsRef) {

      next unless defined $line && $line =~ /\S/;

      my ($tok) = split /\s+/, $line;

      next unless $tok && $tok =~ /@/;

      my ($fs, $snap) = split /@/, $tok, 2;

      push @{ $snaps_by_fs{$fs} }, $snap;

   }

   # nothing to do

   return [] unless keys %snaps_by_fs;

   # figure root filesystem: first snapshot line's fs is the requested root

   my ($first_line) = grep { defined $_ && $_ =~ /\S/ } @$sourceSnapsRef;

   my ($root_fs) = $first_line ? (split(/\s+/, $first_line))[0] =~ /@/ ? (split(/@/, (split(/\s+/, $first_line))[0]))[0] : undef : undef;

   $root_fs ||= (sort keys %snaps_by_fs)[0];

   # helper: find last status entry for a filesystem (status lines contain full snapshot names pool/fs@snap)

   my %last_status_for;

   for my $s (@$statusRef) {

      next unless $s && $s =~ /@/;

      my ($fs, $snap) = split /@/, $s, 2;

      $last_status_for{$fs} = $snap;    # later entries override earlier ones -> last occurrence kept

   }

   # build per-filesystem "from" and "to"

   my %from_for;

   my %to_for;

   foreach my $fs (keys %snaps_by_fs) {

      my $arr = $snaps_by_fs{$fs};

      next unless @$arr;

      $to_for{$fs} = $arr->[-1];

      $from_for{$fs} = $last_status_for{$fs};    # may be undef -> full send required

   }

   # decide if we can do a single recursive send:

   # condition: all 'to' snapshot names are identical

   my %to_names = map { $_ => 1 } values %to_for;

   my $single_to_name = (keys %to_names == 1) ? (keys %to_names)[0] : undef;

   my @commands;

   if ($single_to_name) {

      # check whether any from is missing

      my @from_values = map { $from_for{$_} } sort keys %from_for;

      my $any_from_missing = grep { !defined $_ } @from_values;

      my %from_names = map { $_ => 1 } grep { defined $_ } @from_values;

      my $single_from_name = (keys %from_names == 1) ? (keys %from_names)[0] : undef;

      if ($any_from_missing) {

         # full recursive send from root

         push @commands, sprintf('zfs send -R %s@%s', $root_fs, $single_to_name);

      }

      elsif ($single_from_name) {

         # incremental recursive send

         push @commands, sprintf('zfs send -R -I %s@%s %s@%s',

                           $root_fs, $single_from_name, $root_fs, $single_to_name);

      }

      else {

         # from snapshots differ across children -> fall back to per-filesystem sends

         foreach my $fs (sort keys %to_for) {

            my $to  = $to_for{$fs};

            my $from = $from_for{$fs};

            if ($from) {

               push @commands, sprintf('zfs send -I %s@%s %s@%s', $fs, $from, $fs, $to);

            } else {

               push @commands, sprintf('zfs send %s@%s', $fs, $to);

            }

         }

      }

      # update new status: record newest snap for every filesystem

      foreach my $fs (keys %to_for) {

         push @$newStatusRef, sprintf('%s@%s', $fs, $to_for{$fs});

      }

   } else {

      # not all children share same newest snap -> per-filesystem sends

      foreach my $fs (sort keys %to_for) {

         my $to  = $to_for{$fs};

         my $from = $from_for{$fs};

         if ($from) {

            push @commands, sprintf('zfs send -I %s@%s %s@%s', $fs, $from, $fs, $to);

         } else {

            push @commands, sprintf('zfs send %s@%s', $fs, $to);

         }

         push @$newStatusRef, sprintf('%s@%s', $fs, $to);

      }

   }

   # return arrayref of commands (caller can iterate or join with pipes)

   return \@commands;

}