startSession() hangs

[lahiruchandima]

I am using mongoose to connect to my Mongodb Atlas cluster through my nodejs server.

There is a certain operation which is done as a transaction. I call mongoose.startSession() to start the transaction. Very infrequently, this mongoose.startSession() call hangs indefinitely.

I noticed that there had been a primary node failover in the cluster at the time at which the issue occurred, so this could be caused due to not correctly identifying the failover. I do not have capability to manually do a failover, so I am unable to try to reproduce this by doing failovers.

Following is the code I use to start session.

log.info('starting session');
const mongoSession = await mongoose.startSession();
log.info('session started');

In above code, starting session. gets logged, but session started doesn't get logged when issue occurs.

I connect to the db like below:

const dburl = 'mongodb+srv://myuser:mypassword@myapp.mongodb.net/mydb?retryWrites=true&w=majority';
mongoose.connect(dburl, {useNewUrlParser: true}, err => {
    if (err) {
        log.warn('Error occurred when connecting to database. ' + err);
    }
});

Can this be an issue in Mongoose?

[endze1t]

I'm currently facing the exact same issue.

Starting my app normally with 3 Replicas. Transactions works perfectly. I just shutdown on 1 Replica. Transactions doesn't work anymore, till I restart mongoose and starting the replica again.

[vkarpov15]

@lahiruchandima @endbay what version of Mongoose are you using?

[endze1t]

Newest but I found out, it was probably the MongoDB bug with useUnifiedTopology: true here:

https://jira.mongodb.org/browse/NODE-2231?jql=text%20~%20%22useUnifiedTopology%22

Since I've using old deprecated useUnifiedTopology, everything is working without issues anymore.

[marvellouschandan]

In my case, I was creating session the wrong way like you did.

mongoose.startSession()

Rather you should create the session with the mongo connection you created.

I have written a stackoverflow answer after I was able to solve my issue. Please refer if you are still stuck.
https://stackoverflow.com/a/77698358/9148833