bulkSave promise result, updateResult.getWriteErrorCount is not a function

[kYem]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.8.2

Node.js version

20.18.3

MongoDB server version

6.10.0

Typescript version (if applicable)

5.5.4

Description

This seems to only happen from time to time, maybe cause we are sending a large list of updates, potentially (1-5100) updates in bulk save.

    const updateResult = await TrackerValue.bulkSave(toUpdateValues);
   // Error updateResult.getWriteErrorCount is not a function
    result.failCount = updateResult.getWriteErrorCount();
    result.success = true;
    return result;

Steps to Reproduce

Unfortunately not easy way to produce. Will try to create separate isolated case, but hopefully even without it would be easy to narrow down when getWriteErrorCount is not a function

Expected Behavior

Should either throw error or TypeScrip types are not correct, as getWriteErrorCount is not always available?

[vkarpov15]

I'm unable to repro, the following script works as expected:

const mongoose = require('mongoose');

const trackerValueSchema = new mongoose.Schema({ value:{ type: Number, unique: true } });
const TrackerValue = mongoose.model('TrackerValue', trackerValueSchema);

(async () => {
  await mongoose.connect('mongodb://127.0.0.1:27017/test');
  await TrackerValue.deleteMany({});

  const docs = Array.from({ length: 5001 }, (_, i) => new TrackerValue({ value: i }));
  await TrackerValue.insertMany(docs);

  const toUpdateValues = await TrackerValue.find();
  toUpdateValues.forEach((doc) => (doc.value *= 5000));

  const updateResult = await TrackerValue.bulkSave(toUpdateValues);
  console.log(updateResult.getWriteErrorCount());

  await mongoose.disconnect();
})();

Are you passing options to bulkSave()? If you're not passing options to bulkSave() and not using bulkWrite middleware, I'm not sure this particular error is possible. We did find a potential edge case where bulkSave() can theoretically return null, but that wouldn't result in the error message you're seeing. Can you please modify the above repro script to try to demonstrate the issue you're seeing?

[kYem]

Nope, no options, only array of models to be saved.

• no middleware for bulkSave

It only happen a few times recently, that Sentry was able to catch, both cases indicate multiple request happening for the same model.

Given that the actual bulkSave can take 3-6s, it's likely that the same underlying documents are being updated in two separate request 🤔. Even though the logs indicate they are sequential.

Note that model is big, have embedded history within the document (so it can grow for frequently updated entries), it also the large collection, over 5 million documents, with a lot of indexes.

So it's not easy to reproduce, and it happens quite rarely as you can see, these are all the entries from Sentry we have.

I'm on holiday right now. I will try to spend more time on reproducible case once I'm back (10 days)

[vkarpov15]

@kYem can you please try upgrading to 8.12.2 and see if that upgrade fixes the issue?