From 18a7200beee704fe82e554d16d04f27de50a9f30 Mon Sep 17 00:00:00 2001
From: Alice Gaudon <alice@gaudon.pro>
Date: Mon, 8 Mar 2021 12:56:08 +0100
Subject: [PATCH] zsc-sync.sh: reduce ssh calls by preloading remote info

---
 zsc-sync.sh | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/zsc-sync.sh b/zsc-sync.sh
index 0c4d5b9..517dd64 100755
--- a/zsc-sync.sh
+++ b/zsc-sync.sh
@@ -26,12 +26,22 @@ if ! lockfile-create -p -r 2 "$0"; then
 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=$(ssh $REMOTE zfs get -H -p receive_resume_token -o value "$remote_dataset")
+	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
@@ -60,7 +70,7 @@ handle_dataset() {
 		PREFIX=""
 	fi
 
-	TARGET_REMOTE_DATASET="$REMOTE_ROOT_DATASET/"$(echo -e $DATASET | sed -r "s/\//_/g")
+	TARGET_REMOTE_DATASET="$REMOTE_ROOT_DATASET/"$(echo -e "$DATASET" | sed -r "s/\//_/g")
 
 	echo "[$DATASET -> $TARGET_REMOTE_DATASET]"
 	echo -e
@@ -70,15 +80,14 @@ handle_dataset() {
 
 
 	### Sync existing snapshots ###
-	REMOTE_SNAPSHOTS=($(ssh $REMOTE zfs list -H -t snapshot -o name -s creation $TARGET_REMOTE_DATASET | cut -d"@" -f 2))
-	LOCAL_SNAPSHOTS=($(zfs list -H -t snapshot -o name -s creation $DATASET | cut -d"@" -f 2))
+	REMOTE_SNAPSHOTS=($(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
-		echo "Syncing local snapshot $local_snapshot ..."
 		found=false
 		for remote_snapshot in "${REMOTE_SNAPSHOTS[@]}"; do
 			if [ "$remote_snapshot" = "$local_snapshot" ] ; then
@@ -88,18 +97,16 @@ handle_dataset() {
 		done
 
 		if [ $found = true ] ; then
-			echo "> Found remotely, setting as last snapshot"
+			echo "> $local_snapshot found remotely"
 			FROM_SNAPSHOT=$local_snapshot
 			TO_SNAPSHOT=""
 		else
-			echo "> Needs sync"
+			echo "> $local_snapshot needs sync"
 			TO_SNAPSHOT=$local_snapshot
 		fi
-
-		echo -e
 	done
 
-	echo "Snapshot are synchronized up to $FROM_SNAPSHOT"
+	echo "Snapshots are synchronized up to $FROM_SNAPSHOT"
 	echo -e
 
 	if test ! -z "$TO_SNAPSHOT"; then
@@ -122,21 +129,11 @@ init_subdataset() {
 	PARENT_DATASET=$2
 
 	TARGET_REMOTE_DATASET="$REMOTE_ROOT_DATASET/"$(echo -e $PARENT_DATASET | sed -r "s/\//_/g")"/"${DATASET:$(echo -e "$PARENT_DATASET" | wc -c)}
-	REMOTE_DATASETS=($(ssh $REMOTE zfs list -H -o name -s creation -r $REMOTE_ROOT_DATASET))
 
 
 	resume_transfer "$TARGET_REMOTE_DATASET" || return 0
 
-
-	found=false
-	for d in "${REMOTE_DATASETS[@]}"; do
-		if [ "$TARGET_REMOTE_DATASET" == "$d" ]; then
-			found=true
-			break
-		fi
-	done
-
-	if [ $found = false ]; then
+	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))