spring - How to configure a MongoDB cluster which supports sessions?

Question

I want to explore the new transaction feature of MongoDB and use Spring Data MongoDB. However, I get the exception message "Sessions are not supported by the MongoDB cluster to which this client is connected". Any hint regarding the config of MongoDB 3.7.9 is appreciated.

The stacktrace starts with:

com.mongodb.MongoClientException: Sessions are not supported by the MongoDB cluster to which this client is connected at com.mongodb.MongoClient.startSession(MongoClient.java:555) ~[mongodb-driver-3.8.0-beta2.jar:na] at org.springframework.data.mongodb.core.SimpleMongoDbFactory.getSession(SimpleMongoDbFactory.java:163) ~[spring-data-mongodb-2.1.0.DATAMONGO-1920-SNAPSHOT.jar:2.1.0.DATAMONGO-1920-SNAPSHOT]

Answer 1

I was having the same issue when I was trying to connect it to a single standalone mongo instance, however as written in the official documentation, that Mongo supports transaction feature for a replica set. So, I then tried to create a replica set with all instances on MongoDB 4.0.0, I was able to successfully execute the code. So, Start a replica set (3 members), then try to execute the code, the issue will be resolved.

NB : you can configure a replica set on the same machine for tests https://docs.mongodb.com/manual/tutorial/deploy-replica-set-for-testing/