MongoDB is a free and open source cross-platform, document-oriented database program that can run in cluster mode (using shards and ReplicaSets). In this example, we will run a three-node MongoDB ReplicaSet as that is much easier to configure than a full sharded cluster and is sufficient to demonstrate the principle of storing container state data persistently.
If you would like to learn more about MongoDB and advanced sharded cluster components, please refer to the official documentation: https://docs.mongodb.com/manual/core/sharded-cluster-components/.
Our MongoDB ReplicaSet architecture will look as follows:
The primary node is responsible for managing all write operations, and there can only be one primary in a ReplicaSet. The secondary nodes are only replicating the primary's oplog and apply the data operations so that their...