[buggy silence] Mongoose should throw Error if model created on dumb (without config opts) connection

[nodkz]

In my app I'm switched from default connection to "manual" connections:

// main db file which creates several connections
const db1 = mongoose.createConnection(uri, opts);

// in model file
const User = db1.model('User', UserSchema);
User.find(...);

But in one file I forgot to change default mongoose connection on "manual" connection:

// main db file
// does not setup default connection any more 
// mongoose.connect(uri, opts);

// in model file
const Article = mongoose.model('Article', ArticleSchema);

And when try to make some request on Article, my app hang express requests (freeze them in pending status). How I understood it waiting when default connection will be initialized for proceeding operation. But connection will never be initialized.

@vkarpov15 it will be cool if you somehow add checking if a connection is not initialized and user performs some query operation on model with such dumb connection. I suppose operation (find, count, update ...) should throw an error (cb(err) or reject if promise).

PS. This case very hard to diagnose if using bunch of logic wrappers on top of mongoose. In my case express - react-relay-network-layer:batchExpressMiddleware - graphql-express - graphql-compose - graphql-compose-mongoose - mongoose.

PSS. For me, it's no error anymore, but further users may be blocked by this buggy silence.

[vkarpov15]

Yeah this is something we're planning on changing in 5.0. Buffering was really meant to minimize the number of callbacks necessary but that's much less of a problem now than it was in 2012. Not something we can really change right now without being backwards breaking though.

[vkarpov15]

I think we can close this one now that we have bufferTimeoutMS, which means that you'll at least get some error message after 10 seconds by default if you're using a model that is tied to a connection that you never called connect() on.