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Cluster architecture

Shipper defines two kinds of Kubernetes clusters, management clusters and application clusters.

Management clusters

Management clusters are where Shipper itself runs. It has the Shipper Custom Resource Definitions installed, and is where application developers interact with the Application or Release objects. The management cluster stores the set of Cluster objects and associated Secrets that enable Shipper to connect to the application clusters.

Typically you have one of these per large deployment, or one with a standby.

Application clusters

Application clusters are where Shipper installs and rolls out user workloads. Shipper does not run any custom software in the application clusters: it only needs a service account and associated RBAC configuration.

Patterns

One management, many application

This is the standard arrangement if you have a fleet of Kubernetes clusters that you would like to manage with Shipper. The single management cluster provides application developers with a single place to interface with Shipper's objects and orchestrate their rollouts.

One-and-the-same

It is totally fine if the management cluster and the application cluster are the same. This is how Shipper is developed, and also how you would use Shipper if you only have a single Kubernetes cluster in your infrastructure. You can think about this configuration as using Shipper to provide a better Deployment object, but without any multi-cluster federation.

Multiple management, each with own set of application

While Shipper fully supports namespaces as units of multi-tenancy, it does not yet have any way to limit the set of clusters that an Application can select. So, if your organization has multiple groups of Kubernetes clusters that are consumed by disjoint sets of users, it might make sense to create a management cluster for each group of application clusters that need strong isolation between each other.