#!/bin/bash 

BACKUP_DIR=/home/
ROTATE_CNT=14

SSH_HOST=cluster.univ@se.imbg.org.ua
SSH_PORT=3322
RSYNC_DEST_BASE=/srv/backups/cluster.univ/home
RSYNC_EXCLUDE=${BACKUP_DIR}/.rsync_exclude
RSYNC_SUDO=yes
#RSYNC_VERBOSE=1

# backup from DRBD-master a-node only
grep -q '/mnt/opt' /proc/mounts || exit 0

# lock in case of looooong backup
LOCK_FILE=/run/lock/rsync-home
[ -f "$LOCK_FILE" ] && exit 0
trap "rm -f $LOCK_FILE" EXIT SIGINT SIGTERM
touch "$LOCK_FILE"

rotation_script () {
cat <<END
#!/bin/bash
cd ${RSYNC_DEST_BASE}

idx_get () {
  if [ -f .rotation_idx ]; then
    cat .rotation_idx
  fi
}

idx_set () {
  echo \$1 > .rotation_idx
}

if [ \$1 == "get" ]; then
  idx_get
elif [ \$1 == "set" ]; then
  idx_set \$2
fi
END
}

do_rsync () {
	local localdir=$1
	local remotedir=$2

	local verbosity="--quiet --no-motd"
	[ -n "${RSYNC_EXCLUDE}" ] && excludefile="--delete-excluded --exclude-from=${RSYNC_EXCLUDE}"
	[ -n "${RSYNC_VERBOSE}" ] && verbosity="--human-readable --progress"
	local rshcmd="ssh"
	[ -n "${SSH_PORT}" ] && rshcmd=ssh\ -p\ ${SSH_PORT}
	[ -n "${RSYNC_SUDO}" ] && rsyncpath=--rsync-path=sudo\ rsync
	[ -n "${RSYNC_DRY_RUN}" ] && dry_run=--dry-run\ --itemize-changes

	rsync --archive --links --recursive \
        	--hard-links --perms --owner --group \
		--devices --specials --times --sparse \
	        --compress --compress-level=9 ${excludefile} \
        	--rsh="$rshcmd" "$rsyncpath" --delete ${dry_run} \
		--numeric-ids ${verbosity} $RSYNC_LINK_DEST \
	        "${localdir}" "${remotedir}"
}

# put the simple script to manage /home rotation index
rotation_script | ssh -p ${SSH_PORT} ${SSH_HOST} "cat > $RSYNC_DEST_BASE/rotation_idx.sh"

# execute the script to get last rotation index (to set rsync link-dest)
last_idx=$( ssh -p ${SSH_PORT} ${SSH_HOST} "/bin/bash $RSYNC_DEST_BASE/rotation_idx.sh get" )

if [ -n "$last_idx" ]; then
  RSYNC_LINK_DEST=" --link-dest=../$( printf %02d $last_idx )"
fi

# obtain next index to sync to
next_idx=$(( $last_idx + 1 ))
[ $next_idx -gt $ROTATE_CNT ] && next_idx=1

# rsync it
RSYNC_DEST_URL="${SSH_HOST}:${RSYNC_DEST_BASE}/$( printf %02d $next_idx )"
do_rsync ${BACKUP_DIR} ${RSYNC_DEST_URL}

# increase saved index 
if [ $? -eq 0 ]; then
  ssh -p ${SSH_PORT} ${SSH_HOST} "/bin/bash $RSYNC_DEST_BASE/rotation_idx.sh set $next_idx"
fi

# RHEL GFS2 Guide reccommeds to drop caches to reduces the time required by other nodes 
# to regain ownership of their cluster locks/caches
echo -n 3 >/proc/sys/vm/drop_caches