public void sendResponse(final Message msg) {
        if (!STATE_UPDATER.compareAndSet(this, PENDING, RESPOND)) {
            LOG.warn("A response: {} sent repeatedly!", msg);
            return;
        }
        this.rpcCtx.sendResponse(msg);
    }
RPC request Closure encapsulates the RPC contexts.

@author boyan (boyan@alibaba-inc.com)
@author jiachun.fjc
jraft-core/src/main/java/com/alipay/sofa/jraft/rpc/RpcRequestClosure.java