Mongoose findOne inside async.each - asynchronous

Question

I want to loop through a array and check if the object exists in mongodb and then insert or update.
For which I am using async.each and then call Model.findOne inside it. But the findOne is never getting executed.
exports.ProcessNasVirtualDevices = function ProcessNasVirtualDevicesInfo (virtualDevices, callback)
{
console.log("Started Virtual Devices");
var virtualDeviceIds = [];
if (virtualDevices != null) {
//Loop through the virtual devices
async.each(virtualDevices, function (objVirtualDevice, cb) {
NasVirtualDevice.findOne({ VirtualDeviceName: nasVirtualDeviceName, PhysicalDeviceName: nasPhysicalDeviceName }, function (err, virtualDevices) {
if (err) {
cb("", err);
}
else {
console.log("Found Virtual Device");
if (virtualDevices) {
console.log(nasVirtualDeviceName + " found");
for (virtualDeviceProps in objVirtualDevice) {
console.log("Properties - " + virtualDeviceProps);
virtualDevices[virtualDeviceProps] = objVirtualDevice[virtualDeviceProps];
}
virtualDevices.save(function (err) {
if (err) {
cb("", err);
}
console.log("NasVirtualDevice " + objVirtualDevice.VirtualDeviceName + " updated");
cb();
});
}
else {
var nasVirtualDevice = new NasVirtualDevice();
for (virtualDeviceProps in objVirtualDevice) {
console.log("Properties - " + virtualDeviceProps);
nasVirtualDevice[virtualDeviceProps] = objVirtualDevice[virtualDeviceProps];
}
nasVirtualDevice.save(function (err) {
if (err) {
cb("", err);
}
console.log("NasVirtualDevice " + objVirtualDevice.VirtualDeviceName + " added");
cb();
});
}
}
});
}, function (err) {
// if any of the file processing produced an error, err would equal that error
if (err) {
// One of the iterations produced an error.
// All processing will now stop.
console.log('A Nas Virtual Device Failed');
} else {
console.log('All Virtual Device completed successfully');
}
});
callback("Nas Virtual Devices Completed");
}
}