private static boolean isConnected(final RpcClient rpcClient, final Endpoint endpoint) {
        return rpcClient.checkConnection(endpoint);
    }
Abstract RPC client service based.
@author boyan (boyan@alibaba-inc.com)
@author jiachun.fjc
jraft-core/src/main/java/com/alipay/sofa/jraft/rpc/impl/AbstractClientService.java