Express response doesn't work when using mongoose and async - node.js

Question

I'm using express and mongoose. I have a weird issue when I'm using mocha test to run this endpoint.
exports.broadcastMessages = function(req, res, next) {
User.find({}, function(err, users) {
if(err) return next(err);
var push = function(user, callback) {
user.messages.push(req.body.message);
user.save(function(err) {
callback(err);
});
};
var fin = function(err) {
if (err) {
return next(err);
}
console.log('aaaaaaaaaa');
return res.send('ok');
};
async.each(users, push, fin);
});
};
Then I got a timeout error. There is only one user. So it's not a time issue. And I'm sure res.send('ok') was called. But when I removed user.save(). It worked...
exports.broadcastMessages = function(req, res, next) {
User.find({}, function(err, users) {
if(err) return next(err);
var push = function(user, callback) {
user.messages.push(req.body.message);
callback(err);
};
var fin = function(err) {
if (err) {
return next(err);
}
console.log('aaaaaaaaaa');
return res.send('ok');
};
async.each(users, push, fin);
});
};
I don't know why. Why added one more user.save() it doesn't work? res.send is called but no response.
The version of express is 3.4.7. Mongoose is 3.8.2.

Answer 1

When you say "I got a timeout error" do you mean mocha failed your test for taking too long? If so that is probably a problem in your mocha test itself not calling done() correctly. The above code looks OK to me and I think it should work. Some misc points:
Whenever you have this pattern:
user.save(function(err) {
callback(err);
});
You don't need that extra wrapper function that does nothing but call the callback. Just do:
user.save(callback);
Also, looping through the users and saving each one is much less efficient than just having mongodb do them all for you in a single command:
User.update({}, {$push: {messages: req.body.message}}, function (error) {...});