Concurrency issues with findOneAndUpdate

[guri...@gmail.com]

Our Node.js application uses findOneAndUpdate API in order to update a document. 

Per MongoDB documentation findOneAndModify is atomic API and update document if current approach should avoid data inconsistency or conflicts.  

I've noticed that findOneAndUpdate not always behaves as an atomic API. 

The scenario is as follows:

The application retrieves a document from MongoDB using the following query:

Collection.find({"Posted" : { $exists: false} }, queryOptions)

Thereafter, it calls the findOneAndUpdate API to set the 'Posted' field. 

Collection.findOneAndUpdate(

{"SId" : eventDoc.SId, "SequenceNumber": eventDoc.SequenceNumber, "Posted" : { $exists: false}},

{$set : {"Posted" : "processing"},

{returnOriginal: false},

function(updtErr, updtEventDoc) {

if (updtErr) {

// handle error

}

else if (updtEventDoc.value == null) {

// document was updated by another process

}

else {

// document has been modified successfully 

}

});

I expect the update to modify the document only if the 'Posted' field was not set by another process since the find query.

However, sometimes the same document is updated successfully by multiple processes - findOneAndUpdate returns the modified document with the 'Posted' field set to 'processing' (when I expect only one process to get the updated document while others get 'null').

Another issue I see with the API is that the callback function is never called (although, the document is updated in DB). 

The issue is intermittent. 

Is that a known issue?

MongoDB version is 2.6.9

Thanks 

Anna

[Stephen Steneker]

Hi Anna,

I noticed you've also posted this to Jira as a possible bug (NODE-574) and there is ongoing investigation if anyone would like to watch the issue there.

Regards,

Stephen

[Asya Kamsky]

As Stennie said, the investigation should continue in Jira ticket, however I do want to point out that there is no MongoDB API called findOneAndModify (or findOneAndModify) - that seems to be a Mongoose thing - and under the hood it's probably using findAndModify thought Node.js driver.

Asya

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[guri...@gmail.com]

That's correct, I opened a JIRA ticket and working with the team to provide the requested data for further investigation. 

The issue happens in  Node.js when using findOneAndUpdate API.

Thanks

Anna

[guri...@gmail.com]

Thanks Stephen, I'll use the JIRA ticker for further investigation.