542928492 commented on issue #2223:
URL: https://github.com/apache/rocketmq/issues/2223#issuecomment-668014843
`Reproduce code`
import org.apache.rocketmq.client.common.ThreadLocalIndex;
import org.apache.rocketmq.common.message.MessageQueue;
import java.util.ArrayList;
import java.util.List;
public class MQTEST {
public static List<MessageQueue> messageQueueList = new ArrayList<>();
private static volatile ThreadLocalIndex sendWhichQueue = new
ThreadLocalIndex();
public static void main(String[] args) {
for (int i=0;i<8;i++){
MessageQueue mq = new MessageQueue();
mq.setBrokerName("b1");
mq.setQueueId(i);
mq.setTopic("TT");
messageQueueList.add(mq);
}
for (int i=0;i<8;i++){
MessageQueue mq = new MessageQueue();
mq.setBrokerName("b2");
mq.setQueueId(i);
mq.setTopic("TT");
messageQueueList.add(mq);
}
for (int i=0;i<8;i++){
MessageQueue mq = new MessageQueue();
mq.setBrokerName("b3");
mq.setQueueId(i);
mq.setTopic("TT");
messageQueueList.add(mq);
}
MessageQueue mq = new MessageQueue();
mq.setBrokerName("c1");
mq.setQueueId(0);
mq.setTopic("TT");
messageQueueList.add(mq);
MessageQueue mq2 = new MessageQueue();
mq2.setBrokerName("c2");
mq2.setQueueId(0);
mq2.setTopic("TT");
messageQueueList.add(mq2);
MessageQueue mqtmp = null;
for ( int times = 0; times < 3; times++) {
String lastBrokerName = null == mqtmp ? null :
mqtmp.getBrokerName();
mqtmp= selectOneMessageQueue(lastBrokerName);
System.out.println(mqtmp.getBrokerName());
}
}
public static MessageQueue selectOneMessageQueue(final String
lastBrokerName) {
if (lastBrokerName == null) {
return selectOneMessageQueue();
} else {
int index = sendWhichQueue.getAndIncrement();
for (int i = 0; i < messageQueueList.size(); i++) {
int pos = Math.abs(index++) % messageQueueList.size();
if (pos < 0)
pos = 0;
MessageQueue mq = messageQueueList.get(pos);
if (!mq.getBrokerName().equals(lastBrokerName)) {
return mq;
}
}
return selectOneMessageQueue();
}
}
public static MessageQueue selectOneMessageQueue() {
int index = sendWhichQueue.getAndIncrement();
int pos = Math.abs(index) % messageQueueList.size();
if (pos < 0)
pos = 0;
return messageQueueList.get(pos);
}
}
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