@Override
    public Optional<RequestHandler> getRequestHandler(TenantName tenantName) {
        if (instance == null) {
            throw new IllegalStateException("RpcServer instance has not been registered");
        }
        return instance.getRequestHandler(tenantName);
    }
This is a hack to avoid a cyclic dependency involving {@link RpcServer}, {@link DefaultRpcAuthorizerProvider} and {@link TenantRepository}.

@author bjorncs
configserver/src/main/java/com/yahoo/vespa/config/server/rpc/RpcRequestHandlerProvider.java