Description

Use Case

Running an OpenShift Update Service instance in a cluster is appealing for OpenShift clusters in restricted networks or for administrators that want to provide their own customized upgrade graph data.

About the OpenShift Update Service

The OpenShift Update Service is the on-premise release of Red Hat’s hosted update service. It performs the task of providing upgrade graph information to OpenShift clusters showing the recommended versions that can be safely updated to. This provides administrators with a seamless user experience for applying updates to OpenShift clusters in a restricted network.

Components

Graph Builder fetches OpenShift release payload information (primary metadata) from any container registry (compatible with Docker registry V2 API) and builds a directed acyclic graph (DAG) representing valid upgrade edges. It is responsible for verifying that the graph described by the releases is acyclic and connected.

Policy Engine is in charge of altering a client's view of the graph by applying a set of filters which are defined within the particular Policy Engine instance. Both the input to and the output from Policy Engines is a graph, allowing multiple Policy Engines to be chained together. The first Policy Engine in a chain will fetch its graph from the Graph Builder and the last Policy Engine in a chain will serve the modified graph to the client.

Cluster Version Operator (CVO) (running on the OpenShift 4 cluster) is the end consumer of the release payloads. The client periodically queries the Policy Engine for updates and applies them if available.