Prevent file corruption by writing to a backup file before writing to the real board file

server-data/board-test.json.2019-06-25T11:52:32.336Z.bak

@@ -1 +0,0 @@
-!{"tjp1lbrm74":{"type":"new","id":"tjp1lbrm74","color":"#1913b0","size":27,"x":552,"y":251,"tool":"Text","txt":""},"tjp1lbszvk":{"type":"new","id":"tjp1lbszvk","color":"#1913b0","size":27,"x":957,"y":385,"tool":"Text","txt":""},"tjp1lc73bo":{"type":"new","id":"tjp1lc73bo","color":"#1913b0","size":27,"x":962,"y":370,"tool":"Text","txt":""},"sjp1ly7ztg":{"type":"straight","id":"sjp1ly7ztg","color":"#1913b0","size":10,"x":498,"y":547,"tool":"Straight line","x2":652,"y2":698},"sjp1lybvdw":{"type":"straight","id":"sjp1lybvdw","color":"#1913b0","size":39,"x":407,"y":177,"tool":"Straight line","x2":407,"y2":177},"ljp2gfjkp8":{"type":"line","id":"ljp2gfjkp8","color":"#1913b0","size":10,"tool":"Pencil","_children":[{"type":"child","parent":"ljp2gfjkp8","x":502,"y":430,"tool":"Pencil"},{"type":"child","parent":"ljp2gfjkp8","x":513,"y":433,"tool":"Pencil"},{"type":"child","parent":"ljp2gfjkp8","x":585,"y":434,"tool":"Pencil"},{"type":"child","parent":"ljp2gfjkp8","x":738,"y":405,"tool":"Pencil"},{"type":"child","parent":"ljp2gfjkp8","x":845,"y":398,"tool":"Pencil"},{"type":"child","parent":"ljp2gfjkp8","x":868,"y":399,"tool":"Pencil"}]},"ljp2gfknc8":{"type":"line","id":"ljp2gfknc8","color":"#1913b0","size":10,"tool":"Pencil","_children":[{"type":"child","parent":"ljp2gfknc8","x":655,"y":281,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":675,"y":283,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":825,"y":248,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":999,"y":251,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1037,"y":272,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1089,"y":292,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1113,"y":311,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1130,"y":325,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1143,"y":333,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1160,"y":350,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1174,"y":388,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1169,"y":429,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1151,"y":460,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1136,"y":480,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1131,"y":485,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1127,"y":485,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1120,"y":445,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1108,"y":398,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1107,"y":401,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1098,"y":462,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1097,"y":478,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1094,"y":448,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1092,"y":445,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1084,"y":472,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1084,"y":470,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1082,"y":446,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1077,"y":460,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1075,"y":467,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1068,"y":448,"tool":"Pencil"},{"type":"child","parent":"ljp2gfknc8","x":1060,"y":460,"tool":"Pencil"}]},"sjp2gg3jeu":{"type":"straight","id":"sjp2gg3jeu","color":"#1913b0","size":10,"x":777,"y":743,"tool":"Straight line","x2":1343,"y2":638},"sjp2gg4rts":{"type":"straight","id":"sjp2gg4rts","color":"#1913b0","size":10,"x":1340,"y":649,"tool":"Straight line","x2":1055,"y2":916},"sjp2gg69zj":{"type":"straight","id":"sjp2gg69zj","color":"#1913b0","size":10,"x":929,"y":630,"tool":"Straight line","x2":1422,"y2":1139},"rjp2gg8dyo":{"type":"rect","id":"rjp2gg8dyo","color":"#1913b0","size":10,"x":1060,"y":61,"x2":1394,"y2":245,"tool":"Rectangle"}}

server/boardData.js

@@ -163,14 +163,25 @@ BoardData.prototype.save = function (file) {
 	this.lastSaveDate = Date.now();
 	this.clean();
 	if (!file) file = this.file;
+	var tmp_file = backupFileName(file);
 	var board_txt = JSON.stringify(this.board);
 	var that = this;
-	fs.writeFile(file, board_txt, function onBoardSaved(err) {
+	function afterSave(err) {
 		if (err) {
-			console.trace(new Error("Unable to save the board: " + err));
+			log("board saving error", {
+				'err': err,
+				'tmp_file': tmp_file,
+			});
 		} else {
-			log("saved board", { 'name': that.name });
+			log("saved board", {
+				'name': that.name,
+				'delay_ms': (Date.now() - that.lastSaveDate)
+			});
 		}
+	}
+	fs.writeFile(tmp_file, board_txt, function onBoardSaved(err) {
+		if (err) afterSave(err);
+		else fs.rename(tmp_file, file, afterSave);
 	});
 };
 
@@ -235,10 +246,10 @@ BoardData.load = function loadBoard(name) {
 				boardData.board = {}
 				if (data) {
 					// There was an error loading the board, but some data was still read
-					var backupFileName = boardData.file + '.' + new Date().toISOString() + '.bak';
-					log("Writing the corrupted file to " + backupFileName);
-					fs.writeFile(backupFileName, data, function (err) {
-						if (err) log("Error writing " + backupFileName + ": " + err);
+					var backup = backupFileName(boardData.file);
+					log("Writing the corrupted file to " + backup);
+					fs.writeFile(backup, data, function (err) {
+						if (err) log("Error writing " + backup + ": " + err);
 					});
 				}
 			}
@@ -247,4 +258,8 @@ BoardData.load = function loadBoard(name) {
 	});
 };
 
+function backupFileName(baseName) {
+	return baseName + '.' + new Date().toISOString() + '.bak';
+}
+
 module.exports.BoardData = BoardData;