Post save middleware: reading from database the saved file

[marcosmartinez7]

Prerequisites

• I have written a descriptive issue title

Mongoose version

7.0.2

Node.js version

16.0.14

MongoDB version

5.4

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

20.04

Issue

Hello,

Im using post save middleware and I dont know which is the expected behavior. Didn't found any official docs about this situation:

Basically my FileSchema is implementing a post save

FileSchema.post<FileDocument>('save', async function (doc, next) {
    try {
      const fileModel = this.$model('File');

     
      console.log('the id ', doc._id);
      const file = await fileModel.findById(doc._id);
      console.log('The file ', file);

    } catch (err) {
      console.log('ERROR', err);
      next(err);
    }
  },
});

in that hook im just querying the database for the persisted document.

I get null as a result

If I wrap the entire code into a setTimeout to give the hook 1 second or so, the file is returned.

I was expecting that the post save hook context ensures that the documents are persisted on the database. But it seems that it could happen that there are not present already (the setTimeOut validates that)

Which is the expected behavior?

Regards

[IslandRhythms]

Please update what your mongoose version is, 9.2.0 is not a thing
I'll be testing on latest

[IslandRhythms]

No problems for me. See if you can modify this script to demonstrate your issue.

const mongoose = require('mongoose');

const testSchema = new mongoose.Schema({
  name: String
});

testSchema.post('save', async function (doc, next) {
  console.log('what is doc', doc);
  const model = this.$model('Test');
  const res = await model.findById(doc._id);
  console.log('what is res', res);
});

const Test = mongoose.model('Test', testSchema);

async function run() {
  await mongoose.connect('mongodb://localhost:27017');
  await mongoose.connection.dropDatabase();

  await Test.create({
    name: 'Test Testerson'
  });

  const doc = await Test.findOne();
  doc.name = 'Run Hook';
  await doc.save();
  console.log('done');
}

run();

[marcosmartinez7]

No problems for me. See if you can modify this script to demonstrate your issue.

const mongoose = require('mongoose');

const testSchema = new mongoose.Schema({
  name: String
});

testSchema.post('save', async function (doc, next) {
  console.log('what is doc', doc);
  const model = this.$model('Test');
  const res = await model.findById(doc._id);
  console.log('what is res', res);
});

const Test = mongoose.model('Test', testSchema);

async function run() {
  await mongoose.connect('mongodb://localhost:27017');
  await mongoose.connection.dropDatabase();

  await Test.create({
    name: 'Test Testerson'
  });

  const doc = await Test.findOne();
  doc.name = 'Run Hook';
  await doc.save();
  console.log('done');
}

run();

This works on my local machine but doesn't on MongoAtlas.

I forgot to mention that.

On mongo atlas it seems that I need to add a timeout to delay the execution of the query and give time to the database to persist the object

Does it make sense?

[vkarpov15]

@rahulkumawat30 your comments are off topic. Please open a new issue and follow the issue template.

[vkarpov15]

@marcosmartinez7 the script runs fine for me against Atlas. Can immediately read the update.

Below is what my connection string looks like:

mongodb+srv://foo:bar@host.XYZ.mongodb.net/db?retryWrites=true&w=majority

Can you please provide what your query string looks like, with credentials and hostname excluded? If you don't have w=majority in the connection string and you set a readPreference, this may explain the issue you're seeing.

[marcosmartinez7]

Hi @vkarpov15

"mongodb+srv://XXXX:XXXXX@XXXX.mongodb.net/test"

I do not have the w=majority

Can you explain me why it is related with the issue?

Also my string connection is the "Default" string, so I expected this to work with default configuration. Is not the case?

Thanks

[vkarpov15]

Are you also setting a read preference anywhere? Can you try and see if you still have this issue with w=majority in your connection string?

[marcosmartinez7]

Are you also setting a read preference anywhere? Can you try and see if you still have this issue with w=majority in your connection string?

Not really. Just defaults.

I will try to reproduce it with w=majority. Couldn't find any docs that relate that with this issue, what do you have in mind about it?

Regards

[vkarpov15]

The idea behind w=majority is you're telling MongoDB to not report any write operations (like save()) as complete until the write has replicated to a majority of the replica set. I'm not 100% familiar with how Atlas is configured under the hood, but it is possible that you may need w=majority to avoid this issue. I'd imagine this might be a reason why Atlas always includes w=majority in sample connection strings.

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