localfilesystem storage must fsync writes

Closes #465

red/storage/localfilesystem.js

@@ -121,6 +121,25 @@ function getFileBody(root,path) {
     return body;
 }
 
+/** 
+ * Write content to a file using UTF8 encoding.
+ * This forces a fsync before completing to ensure
+ * the write hits disk.
+ */
+function writeFile(path,content) {
+    return when.promise(function(resolve,reject) {
+        var stream = fs.createWriteStream(path);
+        stream.on('open',function(fd) {
+            stream.end(content,'utf8',function() {
+                fs.fsync(fd,resolve);
+            });
+        });
+        stream.on('error',function(err) {
+            reject(err);
+        });
+    });
+}
+
 var localfilesystem = {
     init: function(_settings) {
         settings = _settings;
@@ -175,8 +194,7 @@ var localfilesystem = {
         } else {
             flowData = JSON.stringify(flows);
         }
-        
-        return nodeFn.call(fs.writeFile, flowsFullPath, flowData);
+        return writeFile(flowsFullPath, flowData);
     },
 
     getCredentials: function() {
@@ -208,8 +226,7 @@ var localfilesystem = {
         } else {
             credentialData = JSON.stringify(credentials);
         }
-        
-        return nodeFn.call(fs.writeFile, credentialsFile, credentialData)
+        return writeFile(credentialsFile, credentialData);
     },
     
     getSettings: function() {
@@ -230,7 +247,7 @@ var localfilesystem = {
         return when.resolve({});
     },
     saveSettings: function(settings) {
-        return nodeFn.call(fs.writeFile,globalSettingsFile,JSON.stringify(settings,null,1),'utf8');
+        return writeFile(globalSettingsFile,JSON.stringify(settings,null,1));
     },
     
     
@@ -254,7 +271,7 @@ var localfilesystem = {
     saveFlow: function(fn,data) {
         var file = fspath.join(libFlowsDir,fn+".json");
         return promiseDir(fspath.dirname(file)).then(function () {
-            return nodeFn.call(fs.writeFile, file, data);
+            return writeFile(file,data);
         });
     },
 
@@ -301,7 +318,7 @@ var localfilesystem = {
             }
         }
         return promiseDir(fspath.dirname(fn)).then(function () {
-            nodeFn.call(fs.writeFile, fn, headers+body);
+            writeFile(fn,headers+body);
         });
     }
 };