Question 303404 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – How can I use multiple MongoDB databases in a NestJS application, with Mongoose?

Overview

FYI : I uploaded a complete project to GitHub. Feel free to download and see for yourself.

I created this project to identify a problem with NestJS, Mongoose and MongoDB. At a high level, the problem is targeting multiple databases from within the project. It seems like NestJS wants to add the suffix 'Model' somewhere in the process.

In my actual application, I am trying to ensure a document is uploaded to MongoDB (…which is easy enough). I have to do some transformation work on the documents later, like on a scheduled job. Once the job is complete, I want to store the transformed document in a separate container.

I use the term "container" generically, here — I don’t care if it’s a database or a collection in the same database.

I would prefer to not modify my data such that I am sticking with the easy route (which means everything goes in the generic fs.files and fs.documents collections in the same database). I mean, the mechanisms are there and pretty well documented, so not sure why this vanilla example isn’t working. Also, yes, I assumed that I would have to use two, separate databases since I don’t imagine MongoDB (let alone Mongoose) provides the mechanisms for renaming those two collections. I am identifying the two, separate connections in the root AppModule as firstCxn and secondCxn so they can be referred to in their respective Module definitions.

A Few Things I’ve Tried

  • I thought there might be some kind of undocumented, explicit naming convention I was missing out on, so I went back and renamed the entities. I added 'Model' to the ends of their names. That’s when I started seeing this whole '...ModelModel' issue.
  • When referencing the models in decorators, I used explicit string values where strings are allowed. For example, in the first.server.ts, I added @InjectModel('First') instead of @InjectModel(FirstModel.name).
  • Added a reference to the FirstModel class in the FirstModule definition, right before the MongooseModule.forFeature(...).
    • This seemed to provide some forward progress. Well…at least, when I changed it in the FirstModule, I started getting the same error for the SecondModule.

Error Output

This is what I get as the output in my debug console…

Debugger attached.                                                                                                                                                                                                                                                                          
(node:27751) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.                                                                                                                                                                  
(Use `node --trace-deprecation ...` to show where the warning was created)                                                                                                                                                                                                                  
[Nest] 27751  - 12/11/2023, 2:57:23 PM     LOG [NestFactory] Starting Nest application...                                                                                                                                                                                                   
[Nest] 27751  - 12/11/2023, 2:57:23 PM     LOG [InstanceLoader] SecondModel dependencies initialized +41ms                                                                                                                                                                                  
[Nest] 27751  - 12/11/2023, 2:57:23 PM     LOG [InstanceLoader] MongooseModule dependencies initialized +0ms                                                                                                                                                                                
[Nest] 27751  - 12/11/2023, 2:57:23 PM     LOG [InstanceLoader] MongooseModule dependencies initialized +0ms                                                                                                                                                                                
[Nest] 27751  - 12/11/2023, 2:57:23 PM   ERROR [ExceptionHandler] Nest can't resolve dependencies of the FirstsService (?). Please make sure that the argument "FirstModelModel" at index [0] is available in the FirstModule context.

It seems that NestJS is looking for something with an additional 'Model' at the end of the name.

Questions

  1. Has anyone seen this before?
    • …anything obvious jumping out?
  2. Are there any good examples of using NestJS, Mongo and Mongoose with multiple databases/collections out there?

Bonus Questions

  1. If teflon is so awesome, why does it stick to the pan?
  2. Will the Sonny ever get some Trix? …is Sonny still even alive?
  3. If a duck eats lunch and then goes swimming right away, does it get a cramp?
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    [Insert :facepalm: HERE]

    Looks like what I was glossing over as a kind of "belt and suspenders" approach is actually just "the approach".

    When injecting the model name in @InjectModel, it is absolutely required to specify the connection name there as well. So, my code looks like this:

    constructor(
    @InjectModel(FirstModel.name, 'firstCxn')
    private firstModel: Model<FirstModel>,
  ) {}

  2. 0 
    **Yes**, we can used multiple mongoose databases in nestjs application.
but nestjs is the first mongoose import considered as a database and ignores the second mongoose import database link.

    The Below code is nestjs for multiple Mongoose database uses:-

app.module.ts

    MongooseModule.forRoot(process.env.DB_URL, {
          dbName: 'atlas_db',
        }),
        MongooseModule.forRoot('mongodb://127.0.0.1:27017/',{
          dbName:'local_db'
        })


    imports: [MongooseModule.forFeature([
        { name: Job.name, schema: JobSchema },
        { name: Local.name, schema: LocalSchema }
      ])],
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