Why you do not use the findAndModify method? This method can create an
document when it is not find via the upsert: true parameter. This method
has the advantage to be atomic like a transaction and you get no problems
when you run multiple node process which execute your findOrCreate method.
Am Sonntag, 29. Juli 2012 03:12:40 UTC+2 schrieb Jaime Morales:
>
> Hi,
>
> I am running into an issue trying to run multiple findOrCreate methods in
> parallel.
>
> Here is the code:
>
> var findOrCreate = exports.findOrCreate = function (data, callback) {
> if (!data.source) {
> return callback(new ParamError('Missing account.source.'));
> }
> if (!data.external_id) {
> return callback(new ParamError('Missing account.external_id'));
> }
>
> Account.findOne({
> source: data.source,
> external_id: data.external_id
> }, function (err, account) {
> if (err) {
> return callback(err);
> }
> if (account) {
> return callback(err, account);
> }
> account = new Account(data);
> account.save(function (err) {
> return callback(err, account);
> });
>
> });
>
> };
>
> The issue is that I may have multiple queries for the same
> source/external_id combo. I am using async.parallel to handle them. But
> since the callbacks in mongoose are pushed onto the next tick, I end up in
> a situation where
>
> 1. a find is performed (pushing the create to the next tick)
> 2. another find is performed for the same source/external_id (pushing
> the create to the next tick)
> 3. a create is performed (for the first find)
> 4. an attempt is made to create again, but this time a duplicate key
> error is thrown (since I already created that account)
>
> I originally tried to get around this by doing an upsert instead of find
> or create, but that didn't work since I need access the the resulting item.
> I am not sure what the best way to handle this scenario is. any ideas?
>
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