...
The design proposes to enhance the current concept of HA node groups by enabling organization administrators to create HA /CA node groups at any time in the lifecycle of a node. Further, the design proposes to loosen the current restriction that all services deployed to a node in an HA /CA group are deployed on all nodes in the group, enabling the use of heterogeneous node equipment within a group. Note that for the purposes of this design, the HA node group concept is intended to provide both HA and CA for the services running on those nodes. Following are the key design constraints which define a new HA /CA node group concept:
- Nodes in an HA group MAY have different node policies.
- Adding a node to an HA Group MUST NOT terminate/restart running services.
- Nodes MAY be placed into an HA Group after node registration.
- A node MUST be in 0 or 1 HA Groups. A node MUST NOT be in more than 1 HA Group.
- A node specifies the other nodes in it's HA Group by Id. All nodes in an HA Group MUST specify all the other nodes in the group. Can we get the exchange to enforce this part of the model?
- A user MUST have permission to modify all the node's (resources) in an HA Group in order to form the group.
- A service that is deployed to all the nodes in an HA Group MUST be upgraded in a rolling restart in order to avoid a complete outage of the service.
- The node agent on nodes in an HA Group MUST be upgraded in a rolling restart in order to avoid a complete outage of the agent itself.
...