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#! /usr/bin/env perl

#    snapShot: Manage ZFS snapshots

#    see http://wiki.linuxservertech.com for additional information

#    Copyright (C) 2022  R. W. Rodolico

#

#    version 1.0, 20220423

#       Initial Release

#

#

#    This program is free software: you can redistribute it and/or modify

#    it under the terms of the GNU General Public License as published by

#    the Free Software Foundation, either version 3 of the License, or

#    (at your option) any later version.

#

#    This program is distributed in the hope that it will be useful,

#    but WITHOUT ANY WARRANTY; without even the implied warranty of

#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

#    GNU General Public License for more details.

#

#    You should have received a copy of the GNU General Public License

#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

#

# Warning, this script requires non-standard Perl modules YAML::Tiny and Hash::Merge

# Under Debian:  apt install libyaml-tiny-perl libhash-merge-simple-perl

# Under FreeBSD: cpan -i Hash::Merge::Simple YAML::Tiny

use strict;

use warnings;

use Data::Dumper;

use Time::Local;

use POSIX qw(strftime);

use YAML::Tiny; # apt-get libyaml-tiny-perl under debian, BSD Systems: cpan -i YAML::Tiny

use Hash::Merge::Simple qw/ merge clone_merge /; # apt install libhash-merge-simple-perl or cpan -i Hash::Merge::Simple

# globals

my $CONFIG_FILE_NAME = 'snapShot.yaml';

# This will be read in from snapShot.yaml

my $config;

#

# find where the script is actually located as cfg should be there

#

sub getScriptLocation {

   use strict;

   use File::Spec::Functions qw(rel2abs);

   use File::Basename;

   return dirname(rel2abs($0));

}

#

# Read the configuration file from current location 

# and return it as a string

#

sub readConfig {

   my $scriptLocation = &getScriptLocation();

   if ( -e "$scriptLocation/$CONFIG_FILE_NAME" ) {

      my $yaml = YAML::Tiny->read( "$scriptLocation/$CONFIG_FILE_NAME" );

      # use clone_merge to merge conf file into $config

      # overwrites anything in $config if it exists in the config file

      $config = clone_merge( $config, $yaml->[0] );

      return 1;

   }

   return 0;

}

# parse one single line from the output of `zfs list [-t snapshot]`

sub parseListing {

   my ($line,$keys) = @_;

   chomp $line;

   my %values;

   @values{@$keys} = split( /\s+/, $line );

   return \%values;

}      

# this will parse the date out of the snapshots and put the values into

# the hash {'date'}

sub parseSnapshots {

   my ( $snapShots, $config) = @_;

   my $keys = $config->{'snapshot'}->{'parseFields'};

   foreach my $snapShot ( keys %$snapShots ) {

      my %temp;

      # run the regex, capture the output to an array, then populate the hash %temp

      # using the regex results as the values, and $keys as the keys

      @temp{@$keys} = ( $snapShot =~ m/$config->{'snapshot'}->{'parse'}/ );

      # while we're here, calculate the unix time (epoch). NOTE: month is 0 based

      $temp{'unix'} = timelocal( 0,$temp{'minute'},$temp{'hour'},$temp{'day'},$temp{'month'}-1,$temp{'year'} );

      # put this into our record

      $snapShots->{$snapShot}->{'date'} = \%temp;

   }

}

# run $command, then parse its output and return the results as a hashref

# $command is one of zfs list or zfs list -t snapshot

# In other words, get all datasets/volumes or get all snapshots

sub getListing {

   my ($configuration, $regex, $command )  = @_;

   my %dataSets;

   # get all datasets/volumes or snapshots

   my @zfsList = `$command`;

   foreach my $thisSet ( @zfsList ) {

      # parse the line into its portions. The only one we use right now is name

      my $temp = &parseListing( $thisSet, $configuration->{'listingKeys'} );

      if (  $temp->{'name'} =~ m/^($regex)$/ ) { # it matches the regex we're using, so save it

         $dataSets{$temp->{'name'}} = $temp;

      }

   }

   return \%dataSets; # return all entries we are looking for

}

# will convert something like 1 day to the number of seconds (86400) for math.

# month and year are approximations (30.5 day = a month, 365.2425 days is a year)

# For month and year, use the int function to convert back to integer

sub period2seconds {

   my ($count, $unit) = ( shift =~ m/\s*(\d+)\s*([a-z]+)\s*/i );

   $unit = lc $unit;

   if ( $unit eq 'hour' ) {

      $count *= 3600;

   } elsif ( $unit eq 'day' ) {

      $count *= 86400;

   } elsif ( $unit eq 'week' ) {

      $count *= 864000 * 7;

   } elsif ( $unit eq 'month' ) {

      $count *= int( 864000 * 30.5 );

   } elsif ( $unit eq 'year' ) {

      $count *= int( 86400 * 365.2425 );

   } else {

      die "Unknown units [$unit] in period2seconds\n";

   }

   return $count;

}

# Merges datasets, snapshots and some stuff from the configuration into the datasets

# hash. After this, $config and $snapshots should no longer be necessary

sub mergeData {

   my ($datasets,$snapshots,$config) = @_;

   my $confKeys = $config->{'datasets'};

   foreach my $thisDataset ( keys %$datasets ) {

      # go through each configuration entry and see if we match the current dataset

      foreach my $conf (keys %$confKeys ) {

         if ( $thisDataset =~ m/^$conf$/ ) { # found it, so store the configuration values into the dataset

            $datasets->{$thisDataset}->{'recursive'} = $confKeys->{$conf}->{'recursive'};

            $datasets->{$thisDataset}->{'frequency'} = &period2seconds( $confKeys->{$conf}->{'frequency'} );

            $datasets->{$thisDataset}->{'retention'} = &period2seconds( $confKeys->{$conf}->{'retention'} );

            last; # there is only one, so no need to process any more for this configuration key

         } # if

      } # foreach

      # do the same for the snapshots we found; bind them to the data set

      foreach my $snapshot ( keys %$snapshots ) {

         if ( $snapshot =~ m/^$thisDataset@/ ) { # this is a match

            # copy the snapshot into the dataset

            $datasets->{$thisDataset}->{'snapshots'}->{$snapshot} = $snapshots->{$snapshot};

            # track the latest snapshot (we use this to decide whether it is time to add a new one)

            $datasets->{$thisDataset}->{'lastSnap'} = $snapshots->{$snapshot}->{'date'}->{'unix'}

               if ! defined( $datasets->{$thisDataset}->{'lastSnap'} ) || $datasets->{$thisDataset}->{'lastSnap'} < $snapshots->{$snapshot}->{'date'}->{'unix'};

            # delete the snapshot, to free up memory

            delete $snapshots->{$snapshot};

         } # if

      } # foreach

   } # foreach

} # sub mergeData

# check to see if a particular snapshot is ready to be destroyed, ie right now is greater than the retention period

# if $recurive is true, add the '-r' to the command to do a recursive destroy

sub checkRetention {

   my ( $retentionPeriod, $recursive, $snapshots, $now ) = @_;

   my @toDelete; # an array of destroy commands

   foreach my $thisSnapshot ( keys %$snapshots ) {

      # print "checking $thisSnapshot\n\tNow: $now\n\tDate: $snapshots->{$thisSnapshot}->{date}->{unix}\n\tRetention: $retentionPeriod\n\n";

      if ( $now - $snapshots->{$thisSnapshot}->{'date'}->{'unix'} > $retentionPeriod ) { # it is too old

         push ( @toDelete, ( 'zfs destroy ' . ($recursive ? '-r ' : '') . $thisSnapshot ) ); # list it to be destroyed

      }

   }

   return @toDelete; # just return the list of destroy commands to be executed

}   

# just return the command to create a new snapshot. Very simple, but I wanted the code to be isolated in case something needed

# to change. Basically, zfs snapshot [-r] datasetname@template

sub makeSnapshot {

   my ( $datasetName, $recursive, $snapshotName ) = @_;

   return 

      'zfs snapshot ' . 

      ($recursive ? '-r ' : '') . 

      $datasetName . $snapshotName;

}

# this is the biggie; everything leads to here. We will take every dataset/volume we found, and decide whether some old snapshots

# need to be destroyed, and whether a new snapshot needs to be created.

sub process {

   my ( $datasets, $now, $snapshotName, $slop ) = @_;

   my @toDelete; # will hold all the destroy commands

   my @toAdd; # will hold all the create commands

   foreach my $thisDataset ( keys %$datasets ) { # Look at each dataset/volume in turn

      # if any snapshots need to be destroyed, add them to @toDelete

      push( @toDelete, 

         &checkRetention( 

         $datasets->{$thisDataset}->{'retention'}, 

         $datasets->{$thisDataset}->{'recursive'}, 

         $datasets->{$thisDataset}->{'snapshots'}, 

         $now )

         );

      # if it is time to add a new snapshot, add it to @toAdd

      if ( $datasets->{$thisDataset}->{'lastSnap'} + $datasets->{$thisDataset}->{'frequency'} - $slop < $now ) {

         push @toAdd, &makeSnapshot( $thisDataset, $datasets->{$thisDataset}->{'recursive'}, $snapshotName )

      }

   }

   # return the actions, deletions first, adds second (executed in that order)

   return ( @toDelete, @toAdd );

}   

# Run 0 or more commands

# the first thing on the stack is a flag for testing

# everything after that is an ordered list of commands to be executed.

# If any command fails, all subsequent commands abort

sub run {

   my $testing = shift;

   return 0 unless @_; # bail if there are no commands to run

   if ( $testing ) { # don't do it, just dump the commands to /tmp/snapShot

      open LOG, ">/tmp/snapShot" or die "could not write to /tmp/snapShot: $!\n";

      print LOG join( "\n", @_ ) . "\n";

      close LOG;

   } else { # actually execute the commands

      my $out; # capture all output

      return 'Not running right now'; # temp while testing

      while ( my $command = shift ) { # for each command on the stack

         $out .= `$command` . "\n"; # add it to $out

         if ( $? ) { # we had an error, add debugging text, the end program

            $out .= "Error executing command\n\t$command\n\t";

            if ($? == -1) {

                $out .= "failed to execute $command: $!";

            } elsif ($? & 127) {

                $out .= sprintf( "child died with signal %d, %s coredump", ($? & 127),  ($? & 128) ? 'with' : 'without' );

            } else {

                $out .= sprintf( "child exited with value %d", $? >> 8 );

            }

            $out .= "\n";

            return $out;

         }

      }

   }

   return 0; # we succeeded

}

&readConfig() or die "Could not read config file: $!\n";

# we're pre-calculating some things so we don't do it over and over for each entry

# grab the time once

my $now = time;

# create the string to be used for all snapshots, using $now and the template provided

my $snapshotName = '@' . strftime($config->{'snapshot'}->{'template'},localtime $now);

# Create the dataset regex by joing all of the regexes defined.

$config->{'dataset_regex'} = '(' . join( ')|(', keys %{ $config->{'datasets'} }  ) . ')' unless $config->{'dataset_regex'};

#print $config{'dataset_regex'} . "\n";

$config->{'snapshot_regex'} = '(' . $config->{'dataset_regex'} . ')@' . $config->{'snapshot'}->{'parse'};

#print $config->{'snapshot_regex'} . "\n\n";

#die Dumper( $config ) . "\n";   

# first, find all datasets which match our keys

my $dataSets = &getListing( $config, $config->{'dataset_regex'}, 'zfs list'  );

# and, find all snapshots that match

my $snapshots = &getListing( $config, $config->{'snapshot_regex'}, 'zfs list -t snapshot'  );

# get the date/time of the snapshots and store them in the hash

&parseSnapshots($snapshots, $config );

# mergeData the snapshots into the datasets for convenience

&mergeData( $dataSets, $snapshots, $config );

# Now, let's do the actual processing

my @commands  = &process( $dataSets, $now, $snapshotName, &period2seconds( $config->{'slop'} ) );

#print join ( "\n", @commands ) . "\n";

my $errors;

print "Error: $errors\n" if $errors = &run( $config->{'TESTING'}, @commands );

# print Dumper( $dataSets );

#print Dumper( $snapshots );

#print join ("\n", sort keys( %$dataSets ) ) . "\n\n";

#print join( "\n", sort keys( %$snapshots ) ) . "\n";

1;