同步发送消息，失败重试

同步发送消息的失败重试
同步模式下，最多发送 3 次，当前轮次发送失败，下次选择另外一个 broker（如果存在）发送
如果设置了 sendLatencyFaultEnable 参数，会把当前的 broker 隔离一段时间

发送失败的情形
1. 消息未发出

// 消息未发出，通过 ChannelFuture 的状态得知
channel.writeAndFlush(request).addListener(new ChannelFutureListener() {
    @Override
    public void operationComplete(ChannelFuture f) throws Exception {
        if (f.isSuccess()) {
            responseFuture.setSendRequestOK(true);
            return;
        } else {
            responseFuture.setSendRequestOK(false);
        }

        responseTable.remove(opaque);
        responseFuture.setCause(f.cause());
        responseFuture.putResponse(null);
        log.warn("send a request command to channel <" + addr + "> failed.");
    }
});

2. 消息发出，等待响应超时

RemotingCommand responseCommand = responseFuture.waitResponse(timeoutMillis);

3. 消息发出，响应错误

 

当消息发送成功，等待 broker 的响应时发生超时，客户端有理由认为是网络不好，数据没有到达 broker，因此重复发送消息，也就是这种情况会导致 broker 存在重复消息。当发生 RemotingException 或 MQClientException 时，会重复发送。

// org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#sendDefaultImpl
for (; times < timesTotal; times++) {
    String lastBrokerName = null == mq ? null : mq.getBrokerName();
    MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName);
    if (mqSelected != null) {
        mq = mqSelected;
        brokersSent[times] = mq.getBrokerName();
        try {
            beginTimestampPrev = System.currentTimeMillis();
            if (times > 0) {
                //Reset topic with namespace during resend.
                msg.setTopic(this.defaultMQProducer.withNamespace(msg.getTopic()));
            }
            long costTime = beginTimestampPrev - beginTimestampFirst;
            if (timeout < costTime) {
                callTimeout = true;
                break;
            }

            sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout - costTime);
            endTimestamp = System.currentTimeMillis();
            this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false);
            switch (communicationMode) {
                case ASYNC:
                    return null;
                case ONEWAY:
                    return null;
                case SYNC:
                    if (sendResult.getSendStatus() != SendStatus.SEND_OK) {
                        if (this.defaultMQProducer.isRetryAnotherBrokerWhenNotStoreOK()) {
                            continue;
                        }
                    }

                    return sendResult;
                default:
                    break;
            }
        } catch (RemotingException e) {
            endTimestamp = System.currentTimeMillis();
            this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
            log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
            log.warn(msg.toString());
            exception = e;
            continue;
        } catch (MQClientException e) {
            endTimestamp = System.currentTimeMillis();
            this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
            log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
            log.warn(msg.toString());
            exception = e;
            continue;
        } catch (MQBrokerException e) {
            endTimestamp = System.currentTimeMillis();
            this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, true);
            log.warn(String.format("sendKernelImpl exception, resend at once, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
            log.warn(msg.toString());
            exception = e;
            switch (e.getResponseCode()) {
                case ResponseCode.TOPIC_NOT_EXIST:
                case ResponseCode.SERVICE_NOT_AVAILABLE:
                case ResponseCode.SYSTEM_ERROR:
                case ResponseCode.NO_PERMISSION:
                case ResponseCode.NO_BUYER_ID:
                case ResponseCode.NOT_IN_CURRENT_UNIT:
                    continue;
                default:
                    if (sendResult != null) {
                        return sendResult;
                    }

                    throw e;
            }
        } catch (InterruptedException e) {
            endTimestamp = System.currentTimeMillis();
            this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false);
            log.warn(String.format("sendKernelImpl exception, throw exception, InvokeID: %s, RT: %sms, Broker: %s", invokeID, endTimestamp - beginTimestampPrev, mq), e);
            log.warn(msg.toString());

            log.warn("sendKernelImpl exception", e);
            log.warn(msg.toString());
            throw e;
        }
    } else {
        break;
    }
}