Kubernetes users running on premises that want an easy way to expose their services outside a cluster on their datacenter network can use external-IPs.
Although external-IPs are simple, they represent a single point of failure for the service and require manual allocation and configuration on the nodes. When there are many to configure, this can be tedious and prone to error. Romana VIPs are a solution to these problems.
Romana VIPs are defined by an annotation in a service spec. Romana then automatically brings up that IP on a node. Romana chooses a node with a pod running locally to avoid network latency within the cluster. When a node with a Romana VIP fails, Romana will bring up the VIP on a new node, providing failover for external services.
Romana VIPs are useful for exposing services on datacenter LANs that only need simple kubeproxy load balancing across pods. Romana VIPs can also be used to expose individual pods when a stable IP is required, such as Cassandra and other Big Data applications. Romana VIPs work in conjunction with Romana DNS, which can be deployed as a service discovery mechanism for individual pods exposed outside of a cluster.
Romana VIP failover requires that all nodes be on the same network segment. Addresses for Romana VIPs must be manually provisioned on the network.
The example below shows a RomanaIP (192.168.99.101) configured on a node for
the nginx service by adding the romanaip annotation to the spec.
...
kind: Service
metadata:
name: nginx
annotations:
romanaip: '{"auto": false, "ip": "192.168.99.101"}'
...
The complete service spec is available here