unhandledRejection MongoServerError: Transaction with { txnNumber: 4 } has been committed

[Raz_Buchnik]

I have an express endpoint that updates a user entity - just putting some data into its document.
The update is done using transaction with a session.
It works - if I abort, the user entity remains without any change - and if I commit the change applies.

However there some weird issues with that. Because if I do the same operation, or just any other HTTP requests to the backend api - even requests that sent to another endpoints - over and over again, then I try the same operation of updating the same user entity, and I got this error:

unhandledRejection MongoServerError: Transaction with { txnNumber: 4 } has been committed.

I have read the docs carefully and there is not a single place stating how to work with the sessions.

1. Should I create one session for the whole mongo client to be reused for every transaction, and just when gracefully shutting down the node process, should I also end the session? (just before doing client.close() )?

2. Should I create a new session for every transaction (on the same mongo client), and just after either commit or abort to also end the session?

I have tried both to solve the issue I have with these but both of them yield the same results.

Also, a general question: should I interact with the database 100% with transactions? is it a good or bad practice?

[Kushagra_Kesav]

Hey @Raz_Buchnik,

Welcome to the MongoDB Community

@Raz_Buchnik

The update is done using transaction with a session.
It works - if I abort, the user entity remains without any change - and if I commit the change applies.

It is advisable to minimize the use of transactions in your workflow by ensuring that your schema is designed to primarily target a single document with each update, approximately 99.9% of the time. Transactions should be used less and should be very much reserved for exceptional cases or edge-case scenarios.

@Raz_Buchnik

1. Should I create one session for the whole mongo client to be reused for every transaction, and just when gracefully shutting down the node process, should I also end the session? (just before doing client.close() )?
2. Should I create a new session for every transaction (on the same mongo client), and just after either commit or abort to also end the session?

You can reuse a session for multiple transactions. Please refer to the Transactions and Sessions documentation to read more.

@Raz_Buchnik

should I interact with the database 100% with transactions? is it a good or bad practice?

It is recommended to minimize the use of transactions to avoid increased contention. Typically, you should do less operation (< 1%) using transactions.

I hope it helps. Please let us know if you have any further questions related to the above information.

Best regards,
Kushagra