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• To use MongoDB Transactions - we have to have the MongoDB setup in ReplicSet mode AND we have to make configuration/setup changes with our ESR Microservices.

MongoDB ReplicaSets

Simply put, a MongoDb ReplicaSet is a cluster in primary/secondary mode. All writes are sent to the master and then the data is propagated to the secondaries. You can setup a MongoDB ReplicaSet with just one node - this is good for testing Transactions but a single node ReplicaSet is not a good idea for production use cases.

If a MongoDB is setup in ReplicaSet mode, it will generally have “replicaSet=” within it’s MongoDB connection string. Here’s an example of a mongodb connection string for a replicaset:mongodb://txuser:txpass@mongo1.hee.com:27011,mongo2.hee.com:27012,mongo3.hee.com:27013/transdb?authSource=transdb&replicaSet=rs0

• For further details see

  • https://docs.mongodb.com/manual/reference/connection-string/

  • https://docs.mongodb.com/manual/tutorial/deploy-replica-set/

  • https://docs.mongodb.com/manual/replication/

NOTE: if we want to use MongoDB Transactions we must point to a MongoDB in ReplicaSet mode AND setup the code to use Transactions.

• We cannot have the code to setup to use transactions and point to a MongoDB not in ReplicaSet (Transaction supporting) mode.

• We cannot have the code setup without transaction support and point to a MongoDB in ReplicaSet (Transaction supporting) mode.

• If we have the code setup with transaction support we must point to a MongoDB in ReplicaSet (Transaction supporting mode)

• If the code is setup without transaction support we must point to a MongoDB not in ReplicSet (Transaction supporting mode)

In the code, there are 3 steps required to use MongoDB Transactions.

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