server-scripts/zsc-sync.sh

#!/bin/bash

# ZSC-Sync - zfs snapshot cron sync
# Usage: <script> <remote> <remote_dataset>

ZSC_CONFIG="$HOME/.zsc"

REMOTE=$1
if test -z "$REMOTE"; then
	echo "No remote specified"
	exit -1
fi

REMOTE_ROOT_DATASET=$2
if test -z "$REMOTE_ROOT_DATASET"; then
	echo "No remote root dataset specified"
	exit -1
fi


### LOCK ###
echo "Locking $0"
if ! lockfile-create -p -r 2 "$0"; then
	echo "Another backup is running, aborting"
	exit 49
fi


echo "Fetching remote snapshots..."
remote_snapshots=$(ssh $REMOTE zfs list -H -t snapshot -o name -s creation)

echo "Fetching subdatasets..."
remote_subdatasets=$(ssh $REMOTE zfs list -H -o name -s creation -r "$REMOTE_ROOT_DATASET")

echo "Fetching resume tokens..."
resume_tokens=$(ssh $REMOTE zfs get -H -p receive_resume_token -o name,value -t filesystem)


### Resume existing transfer ###
# Returns 0 if no action was performed, 1 if a transfer was resumed and finished successfully, -1 if there was an error during resumed transfer
resume_transfer() {
	remote_dataset=$1

	RESUME_TOKEN=$(echo -e "$resume_tokens" | grep -P "^$remote_dataset\t.*\$" | cut -d$'\t' -f2)
	if [ "$RESUME_TOKEN" != "" ] && [ "$RESUME_TOKEN" != "-" ]; then
		echo "Resuming interrupted transfer..."
		zfs send -v -t "$RESUME_TOKEN" | ssh $REMOTE zfs receive -F -s "$remote_dataset" || return -1
		echo "Resumed transfer finished."
		return 1
	fi

	return 0
}


handle_dataset() {
	DATASET=$1
	RECURSIVE=$2
	D=$3
	W=$4
	M=$5
	Y=$6

	PREFIX=$7
	if test -z "$PREFIX"; then
		PREFIX="zsc-"
	fi

	if test "!no_prefix!" = "$PREFIX"; then
		PREFIX=""
	fi

	TARGET_REMOTE_DATASET="$REMOTE_ROOT_DATASET/"$(echo -e "$DATASET" | sed -r "s/\//_/g")

	echo "[$DATASET -> $TARGET_REMOTE_DATASET]"
	echo -e


	resume_transfer "$TARGET_REMOTE_DATASET" || return 0


	### Sync existing snapshots ###
	REMOTE_SNAPSHOTS=($(echo -e "$remote_snapshots" | grep "$TARGET_REMOTE_DATASET@" | cut -d"@" -f 2))
	LOCAL_SNAPSHOTS=($(zfs list -H -t snapshot -o name -s creation "$DATASET" | cut -d"@" -f 2))

	echo "Remote snapshots: ${#REMOTE_SNAPSHOTS[@]}"
	echo "Local snapshots: ${#LOCAL_SNAPSHOTS[@]}"
	echo -e

	for local_snapshot in "${LOCAL_SNAPSHOTS[@]}"; do
		found=false
		for remote_snapshot in "${REMOTE_SNAPSHOTS[@]}"; do
			if [ "$remote_snapshot" = "$local_snapshot" ] ; then
				found=true
				break
			fi
		done

		if [ $found = true ] ; then
			echo "> $local_snapshot found remotely"
			FROM_SNAPSHOT=$local_snapshot
			TO_SNAPSHOT=""
		else
			echo "> $local_snapshot needs sync"
			TO_SNAPSHOT=$local_snapshot
		fi
	done

	echo "Snapshots are synchronized up to $FROM_SNAPSHOT"
	echo -e

	if test ! -z "$TO_SNAPSHOT"; then
		echo "Synchronizing snapshots from $FROM_SNAPSHOT to $TO_SNAPSHOT ..."

		if test ! -z "$FROM_SNAPSHOT"; then
			incr="-I $FROM_SNAPSHOT"
		fi
		if [ $RECURSIVE = true ] ; then
			recu="-R"
		fi
		zfs send -v -p $recu $incr "$DATASET@$TO_SNAPSHOT" | ssh $REMOTE zfs receive -F -s "$TARGET_REMOTE_DATASET" || return 1

		echo "Done"
	fi
}

init_subdataset() {
	DATASET=$1
	PARENT_DATASET=$2

	TARGET_REMOTE_DATASET="$REMOTE_ROOT_DATASET/"$(echo -e $PARENT_DATASET | sed -r "s/\//_/g")"/"${DATASET:$(echo -e "$PARENT_DATASET" | wc -c)}


	resume_transfer "$TARGET_REMOTE_DATASET" || return 0

	if [ $(echo -e "$remote_subdatasets" | grep -e "^$TARGET_REMOTE_DATASET\$" | wc -l) -eq 0 ]; then
		echo "Subdataset not found on $TARGET_REMOTE_DATASET, initializing..."

		LOCAL_SNAPSHOT=($(zfs list -H -t snapshot -o name -s creation "$DATASET" | cut -d"@" -f 2 | tail -n 1))

		if test -z "$LOCAL_SNAPSHOT"; then
			echo "No local snapshot"
			return 1
		fi

		echo "[$DATASET@$LOCAL_SNAPSHOT -> $TARGET_REMOTE_DATASET]"
		zfs send -v -p "$DATASET@$LOCAL_SNAPSHOT" | ssh $REMOTE zfs receive -F -s "$TARGET_REMOTE_DATASET" || return 1

		echo -e "Done"
	fi
}


for line in $(cat "$ZSC_CONFIG") ; do
	IFS=: read dataset recursive d w m y prefix <<< "$line"
	echo "| ##### Dataset: $dataset Recursive: $recursive Prefix: $prefix d: $d w: $w m: $m y: $y #####"

	if [ $recursive = "true" ]; then
		SUBDATASETS=($(zfs list -o name | grep "$dataset/"))
		echo -e "| Subdatasets: ${SUBDATASETS[@]}"
		echo -e '|'
		for p in "${SUBDATASETS[@]}"; do
			init_subdataset $p $dataset | awk '{print "| " $0}' || exit 1
		done
	fi

	handle_dataset $dataset $recursive $d $w $m $y $prefix | awk '{print "| " $0}' || exit 1

	echo -e "----------------------------------------------------------------------"
done


### UNLOCK ###
echo "Unlocking $0"
lockfile-remove "$0"