BulkWriter.writeToMultipleCollections breaks transaction support

[IsNull]

We have observed that transactions do not propagate with the new multi collection Bulk update, as soon as multiple collections are involved.
I think I tracked the issue down to here: https://github.com/spring-projects/spring-data-mongodb/blob/main/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/BulkWriter.java#L110C1-L111C1

The BulkWritter.writeToMultipleCollections uses MongoTemplate.doWithClient(client -> client.bulkWrite(, and does not use the overload with the client-session. In contrast to this, the single collection path uses MongoTemplate.execute which seems to pass on the client session.

I hope this helps to resolve the issue.

[christophstrobl]

Thank you for getting in touch. If you'd like us to spend some time investigating, please take the time to provide a complete minimal sample (something that we can unzip or git clone, build, and deploy) that reproduces the problem.

[n0daft]

I've created a minimal sample project which uses TestContainers to illustrate that the new BulkWriter is not capable of handling Transactions. The tests show this by showing rollback not working as well as read-your-own-writes not working while being seemingly within the transaction.

For details see the Readme of the project. Hope this helps.