High Availability on K8S

HA solutions for MongoDB

In production environments it's recommended to use a managed database service from a cloud provider, Azure, AWS and Google Cloud all provide MongoDB compatible services. These services have built-in HA and can scale dynamically depending on the required load.

If a highly available database is required inside the k8s cluster, then there are publicly available solutions that can deploy a MongoDB Replica Set. For a k8s cluster, MongoDB provides an operator for deploying a Replica Set:

https://www.mongodb.com/docs/kubernetes-operator/master/tutorial/deploy-replica-set/

HA deployment for MDSS

MDSS containers can be scaled independently depending on the availability and performance requirements. For example, just the webclientand apigateway pods can be replicated to provide high availability to outside requests and for the web interface.

mdss_components:

  webclient:

    replicas: 3

  apigateway:

    replicas: 3

3rd party services should not be replicated from the helm chart but the can be replaced with managed external services:

• mongodb: The MongoDB database, see above for HA solutions
• rabbitmq: The RabbitMQ service used by MDSS pods to communicate with each other
• redis: Redis cache service

The mongomigrationsservice is used to keep the database up to date at startup and provides no benefits if replicated .