#!/bin/bash

# Author: Carl Baldwin & Alan Pippin
# Description: This script takes a snapshot of the given zfs filesystem.
#              It also employs an intelligent algorithm to roll off,
#              or destroy, old snapshots.

test=0

[ $test == 0 ] && exec >> /var/log/zfs-autosnap.log 2>&1

# This script makes the following assumptions/requirements:
#  * this script only handles one zfs filesystem, a wrapper should be created
#    to handle more
#  * this script handles all snapshots that are named in this format:
#    YYYY-MM-DD.hh.mm
#  * It ignores other snapshots that don't follow this naming convention

# This converts the YYYY-MM-DD.hh.mm format to an integer.
datetime_to_minutes() {
  perl -n -e '/(\d+)-(\d+)-(\d+)\.(\d+)\.(\d+)/; print $1 * 527040 + $2 * 44640 + $3 * 1440 + $4 * 60 + $5,"\n"'
}

datetime_to_minutes2() {
  perl -n -e '/(\d+)-(\d+)-(\d+)\.(\d+)\.(\d+)/; $monthadj=int(($2-1)/3)-1; $minadj=int($5/15); $houradj=int($4/3); print $1 * 1048576 + ( $2 + $monthadj ) * 65536 + $3 * 2048 + ( $4 + $houradj ) * 64 + $5 + $minadj,"\n"'
}

# test: if set to 1, no zfs snapshot commands will be run, they will only be echoed
# filesystem: This is the zfs filesystem to snapshot
# mountpoint: This is the mountpoint of the zfs filesystem to snapshot
# numsnapshots: This number is the number of equally spaced snapshots that should exist over any given period in the past
# maxagedays: This is the maximum number of days to keep any snapshot around for (0=infinite) (default=0).
filesystem=$1
mountpoint=$2
numsnapshots=${3-20}
maxagedays=${4-0}

lockdir="/tmp/zfs-admin-lock"
pool=`echo "$filesystem" | awk -F '/' '{ print $1 }'`

if [ -z "$filesystem" ] || [ -z "$mountpoint" ] || [ -z "$numsnapshots" ] || [ -z "$maxagedays" ]; then
   echo "-E- Usage: $0 <filesystem> <mountpoint> <numsnapshots> <maxagedays>"
   exit 1
fi

if [ ! -d "$mountpoint" ]; then
   echo "-E- Unable to find the mountpoint: $mountpoint"
   exit 1
fi

snapshotdir="${mountpoint}/.zfs/snapshot"
if [ ! -d "$snapshotdir" ]; then
   echo "-E- Unable to find the snapshotdir: $snapshotdir"
   exit 1
fi

# Check to see if this zfs pool has a scrub being performed on it now.
# If it does, we cannot perform any snapshot create or destroy operations.
zpool status $pool | grep scrub: | grep "in progress" > /dev/null 2>&1
if [ $? == 0 ]; then
   echo "-W- The zfs pool '$pool' is currently being scrubbed. Skipping all snapshot operations."
   exit 0
fi

# Get the various components of the date
datetime=${ZFSDATETIME:-$(date +%Y-%m-%d.%H.%M)}

# Create the snapshot for this minute
echo "-I- Creating ${filesystem}@${datetime}"
[ $test == 0 ] && zfs snapshot "${filesystem}@${datetime}"

minutes=$(echo $datetime | datetime_to_minutes)

# Check to ensure the zfs filesystem has not been locked down.
# If it has, we cannot perform any snapshot destroy operations.
if [ -d "$lockdir" ]; then
   echo "-W- The zfs filesystem has been locked down. Skipping snapshot cleanup."
   exit 0
fi

# Trim them down
snapshots=$(ls -d ${snapshotdir}/????-??-??.??.?? 2>/dev/null)
for snapshot in $snapshots; do
  snapminutes=$(echo "$snapshot" | sed 's,.*/,,' | datetime_to_minutes)
  snapminutes2=$(echo "$snapshot" | sed 's,.*/,,' | datetime_to_minutes2)
  age=$((minutes - snapminutes))
  window=1
  while true; do
    if [ $age -lt $((window * numsnapshots)) ]; then
      case $((snapminutes2 % window)) in
        0) ;;
        *)
          snapname=${filesystem}$(echo "$snapshot" |
                       sed 's,/\(.*\)/.zfs/snapshot/\(.*\),@\2,')
          echo "-I- Destroying $snapname"
          [ $test == 0 ] && zfs destroy "$snapname"
        ;;
      esac
      break
    fi
    window=$((window*2))
  done
  if [ $maxagedays -gt 0 ] && [ $age -gt $((maxagedays * 24 * 60)) ]; then
    snapname=${filesystem}$(echo "$snapshot" |
                     sed 's,/\(.*\)/.zfs/snapshot/\(.*\),@\2,')
    echo "-I- Destroying old $snapname"
    [ $test == 0 ] && zfs destroy "$snapname"
  fi
done

true