private static DocapiCommon.ClusterState toProtoClusterState(String stateStr) {
        return DocapiCommon.ClusterState.newBuilder().setStateString(stateStr).build();
    }
Implementation of MessageBus message request/response serialization built around Protocol Buffers.
documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/RoutableFactories80.java