public Target getConnection(final NodeInfo node) {
        Target t = node.getConnection();
        if (t == null || !t.isValid()) {
            t = node.setConnection(supervisor.connect(new Spec(node.getRpcAddress())));
        }
        return t;
    }
Responsible for doing RPC requests to storage nodes.
This class is not thread-safe.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/rpc/RPCCommunicator.java