Multiple connections with models located in separate files

[weblogics]

Do you want to request a feature or report a bug?

feature

What is the current behavior?

When initialising more than one connection (different hosts / servers) its impossible to separate models from the initial app. I have tried to implement useDb(), but this seems to be for the same connection with different DB's hosted on this.

I have also tried to implement mongoose.connections[index].model('ModelName', Schema), this doesn't work if the connection hasn't been run yet (Please note: I'm using mongoose.createConnection()). Using TypeScript imports need to be the first thing in the file and therefore there's no way to create these connections prior to loading the models.

There really needs to be a better way to separate models from connections. Is there nothing that can be done to use a connection such as a useConnection function? The current implementation is unreliable and it's hard to work with.

Has anyone else managed to solve this issue?

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.

MongoDB: 4.0.3
Node: v11.12.0
Mongoose: 5.7.5

[vkarpov15]

useConnection is an interesting idea, but we aren't likely to support it because it encourages changing the connection when using the model.

The right design pattern here is to export a schema, not a model. Then have a separate file that exports a function which registers models on a connection.

import fooSchema from './fooSchema';

export default function(conn) {
  conn.model('Foo', fooSchema);
}

[lauti7]

@vkarpov15 I am having same issue and in the docs, i saw that i have to create exported function but where i am supposed to run this function?

[vkarpov15]

@lauti7 there's a couple possibilities. First is to have separate connection files:

// conn1.js
const config = require('./config');
const mongoose = require('mongoose');

const db = mongoose.createConnection(config.mongodbUri);
require('./decorateModels')(db);

module.exports = db;

// conn2.js
const config = require('./config');
const mongoose = require('mongoose');

const db = mongoose.createConnection(config.mongodbUri);
require('./decorateModels')(db);

module.exports = db;

Where decorateModels() is a function that attaches models to a connection.

Another alternative is to use a DI framework or some other IOC pattern. These days I just use ramda's applySpec() for IOC.

[vkarpov15]

Will close this in favor of #8679