High frequency calls leads to duplicates with findOrCreate in Waterline & Sails - postgresql

Question

How to handle high frequency updateOrCreate requests with Waterline in Sails for a Postgresql database ?
I tried to use findOrCreate and then update the item, I tried findOne and then update or create the item, I tried to put a beforeCreate, a beforeValidation hook method to check if the item exists but without any success.
Should I add an error handler to get errors from the unique index and try again?
In the Waterline docs, there is a warning about it but no direction to solve this problem.
Thank you for any tips.

Answer 1

Should I add an error handler to get errors from the unique index and try again?
That's going to be the only option until such time as Waterline implements transactions. Something like:
// This will hold the found or created user
var user;
// Keep repeating until we find or create a user, or get an error we dont expect
async.doUntil(
function findOrCreate(cb) {
// Try findOrCreate
User.findOrCreate(criteria, values).exec(function(err, _user) {
// If we get an error that is not a uniqueness error on the
// attribute we expect collisions on, bail out of the doUntil
if (err &&
(
!err.invalidAttributes["myUniqueAttribute"] ||
!_.find(err.invalidAttributes["myUniqueAttribute"], {rule: 'unique'})
)
) {
return cb(err);
}
// Otherwise set the user var
// It may still be undefined if a uniqueness error occurred;
// this will just cause doUntil to run this function again
else {
user = _user;
return cb();
}
},
// If we have a user, we are done. Otherwise go again.
function test() {return user},
// We are done!
function done(err) {
if (err) {return res.serverError(err);}
// "user" now contains the found or created user
}
});
Not the prettiest, but it should do the trick.