Does JS Driver Support `appName` in Connection String?

The JS code:

const url = process.env.MONGO_URL;
const mongoClient = await MongoClient.connect(url);

The .env file:


These codes cause the following error:

MongoServerSelectionError: failed to handle command request "ismaster": error processing client metadata: expected app name to be composed of: <appID>:<svc>:<authProvider>, got [object Object]

I think the error shows something wrong with the appName parameter.

I first thought it was a Realm problem, but the connection string properly works in CLI (i.e. the mongo command), so I’m now thinking this is related to JS Driver. (FYI: I’m using ver 3.6.2)

Is this an expected behavior or a bug?

Hi @Toshi,

The Node JS driver with latest versions should work with Realm wire protocols:

Do you see any server side logging for this attempts?


1 Like

Hi Pavel, thanks for the response. Firstly, I can’t find any logs recorded in the Realm UI unfortunately.

Actually, you can reproduce the problem in a couple of minutes:

# in empty directory
npm init -y
npm install mongodb
touch index.js


const MongoClient = require('mongodb');

const main = async () => {
  await MongoClient.connect(MONGO_URL);

main().catch(err => {

If you use a normal Atlas url, it works properly. (i.e. mongodb+srv://<username>:<password>

On the other hand, if you use a Realm url, you’ll see the
expected <appID>:<svc>:<authProvider>, got [object Object]” error.

I’d appreciate it if you could check.

I tried several more attempts with some guesswork (still not working).
I guess there is possibly something wrong with dealing with colons.

1. Using the string copied form Realm UI (“Data Source” page)

The connection string which has


will produce this error:
expected ... <appID>:<svc>:<authProvider>, got [object Object]

2. Using URL encoded one (colon → %3A)


will produce the same error:
expected ... <appID>:<svc>:<authProvider>, got [object Object]

3. Using a plain string without colons


This time the param was not converted to an [object Object].
The error message says it got the string instead:
expected ... <appID>:<svc>:<authProvider>, got application-0-xxxxx

Again, the connection string correctly worked with CLI (the mongo command). It seems it is not working only with Node.js SDK.

1 Like

Is there any solution to this? We are working on migration process that will happen on our servers using old Realm GraphQL and new MongoDB using mongoose.

The problem is that when we connect directly to the cluster, changes are not propagated to the realm so I guess we need to connect as this special mongodb realm url? However, it does not work in Node :frowning:


Has there been any resolution to this. I am encountering this error now.