Sequelizejs model create callback is not running synchronously? - node.js

Question

I'm using Sequelize and PostgreSQL in my node.js application. I have two tables with one-to-one relationship - Customers and Users.
There is foreign key UserId in the Customers table. So, I firstly insert into the Users table and then insert into the Customers with the last inserted UserId. Here is my controller code:
var self = this;
async.each(data, function(row, callback) {
var userData = {
name: row.name,
/** **/
}
// self.User is User model
self.User.create(userData).then(function(user) {
console.log("[User.create] succeeded");
/** **/
// self.Model is Customer model
self.Model.create(cusData).then(function(customer) {
console.log("[Customer.create] succeeded");
/** **/
}).catch(function(err) {
throw err;
}); // EOL self.Model.create
}).catch(function(err) {
throw err;
}); // EOL self.User.create
callback();
}, function(err){
if (err) {
throw err;
}
}
I'm using async.each() to loop the array of 2 records synchronously. When I inserted the two records, the console output is:
[User.create] succeeded
[User.create] succeeded
[Customer.create] succeeded
[Customer.create] succeeded
What I expected is:
[User.create] succeeded
[Customer.create] succeeded
[User.create] succeeded
[Customer.create] succeeded
I think it could be a problem of synchronous flow in asynchronous programming. What am I wrong? I think I'm using the callbacks correctly.

Answer 1

You're initiating the two inserts asynchronously, so you've no guarantee on the order of the follow-up queries. For all you know, depending on locks, you could get the current or your expected result.
To force the order, move the iteration forward from within the inner callback:
self.Model.create(cusData).then(function(customer) {
console.log("[Customer.create] succeeded");
/** move the iterator forward here, using e.g. recursion **/
})