rocketMQTemplate.asyncSend throws ConcurrentModificationException at MessageDecoder.messageProperties2String

Question

I am using rocketmq-spring to send message which version is 2.1.0, sometimes i got ConcurrentModificationException at org.apache.rocketmq.common.message.MessageDecoder.messageProperties2String(MessageDecoder.java:414),the following is a detailed log. Thanks!

#[xx, 10.xx.52] INFO  2022-05-07 15:31:11.043 [XNIO-1 task-74, 29de7f06241a3313, 29de7f06241a3313] com.xx.common.IpProducerService.asyncSendMessage:45 - contentMap{refNo=xx, system=xx, ip=null, platformId=xx, userId=xxx}
#[fp, 10.xx.52] INFO  2022-05-07 15:31:11.043 [XNIO-1 task-74, 29de7f06241a3313, 29de7f06241a3313] com.xx.rocketmq.producer.RocketMqProducer.asyncInfo:19 - -=-=-= [Async Sending Message] -=-=-= 
 Topic                = TOPIC_xx_xx
 Tag                   = 
 MessageId        = null
 DelayLevel        = 0
 Content            = {"refNo":"xx","system":"xx","platformId":"xx","userId":"xx"}

#[fp, 10.xx.52] ERROR 2022-05-07 15:31:11.044 [AsyncSenderExecutor_3, , ] com.xx.rocketmq.producer.ProduceCallBack.onException:32 - asyncSendMessage caused exception.
java.util.ConcurrentModificationException: null
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
    at java.util.HashMap$EntryIterator.next(HashMap.java:1471)
    at java.util.HashMap$EntryIterator.next(HashMap.java:1469)
    at org.apache.rocketmq.common.message.MessageDecoder.messageProperties2String(MessageDecoder.java:414)
    at org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl.sendKernelImpl(DefaultMQProducerImpl.java:790)
    at org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl.sendDefaultImpl(DefaultMQProducerImpl.java:584)
    at org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl.access$300(DefaultMQProducerImpl.java:97)
    at org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl$4.run(DefaultMQProducerImpl.java:511)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
#[xx, 10.xx.52] INFO  2022-05-07 15:31:11.044 [AsyncSenderExecutor_3, , ] com.xx.common.IpProducerService.handleResult:49 - async produce status is F

Answer 1

use different rocketMQTemplates instance to send same message.

asyncSend is doing on ThreadPool in rocketMQTemplates, there are lots of threads there, so you can't send same message(same message use the same propertiy HashMap, not thread-safe) using different rocketMQTemplates.