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Posted to dev@rocketmq.apache.org by GitBox <gi...@apache.org> on 2022/04/12 11:21:00 UTC
[GitHub] [rocketmq] mz0113 opened a new issue, #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
mz0113 opened a new issue, #4154:
URL: https://github.com/apache/rocketmq/issues/4154
mq.setBrokerName(notBestBroker);
mq.setQueueId(tpInfo.getSendWhichQueue().getAndIncrement() % writeQueueNums);
this method of selectOneMessageQueue is executed by multiThread when send a message but the mq (messageQueue) is a shared object , thread A modify it`s brokerName to brokerB,but have not modify it queueId, still 1 , then thread B send msg and use this queue,but now,this queue `s brokerName is brokerB but it`s queueId is 1, in this case , wo can`t sure that brokerB really have queue which queueId is 1
Isn't that really a problem?
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[GitHub] [rocketmq] ni-ze commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
ni-ze commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097608746
```java
int writeQueueNums = tpInfo.getQueueIdByBroker(notBestBroker);
...
mq.setBrokerName(notBestBroker);
mq.setQueueId(tpInfo.getSendWhichQueue().incrementAndGet() % writeQueueNums);
```
a messageQueue's brokerName and queueId is consistent, because writeQueueNums is belong to the same brokerName, which is notBestBroker in this case.
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[GitHub] [rocketmq] mz0113 commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
mz0113 commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097543543
> I do not think so.
>
> ```java
> tpInfo.getSendWhichQueue().incrementAndGet()
> ```
>
> the index is a thread local variable, would change with thread.if thread switched, index will change.
It is precisely because the index has changed that other threads have the opportunity to use this queue
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[GitHub] [rocketmq] mz0113 closed issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
mz0113 closed issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
URL: https://github.com/apache/rocketmq/issues/4154
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[GitHub] [rocketmq] lwclover commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
lwclover commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097467953
> 
>
> mq.setBrokerName(notBestBroker); mq.setQueueId(tpInfo.getSendWhichQueue().getAndIncrement() % writeQueueNums);
>
> this method of selectOneMessageQueue is executed by multiThread when send a message but the mq (messageQueue) is a shared object , thread A modify it`s brokerName to brokerB,but have not modify it queueId, still 1 , then thread B send msg and use this queue,but now,this queue `s brokerName is brokerB but it`s queueId is 1, in this case , wo can`t sure that brokerB really have queue which queueId is 1
>
> Isn't that really a problem?
I think you are right, to be more precise, constructors should be used.
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[GitHub] [rocketmq] ni-ze commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
ni-ze commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097489919
I do not think so.
```java
tpInfo.getSendWhichQueue().incrementAndGet()
```
the index is a thread local variable, would change with thread.if thread switched, index will change.
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[GitHub] [rocketmq] lwclover commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
lwclover commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097511342
> I do not think so.
>
> ```java
> tpInfo.getSendWhichQueue().incrementAndGet()
> ```
>
> the index is a thread local variable, would change with thread.if thread switched, index will change.
There's a mod
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[GitHub] [rocketmq] MatrixHB commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
MatrixHB commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1100837679
The core problem is that the shared object `messageQueueList.get(pos)` cannot be modified after being obtained.
I've proposed a PR [#4179 ](https://github.com/apache/rocketmq/pull/4179) please review it. @mz0113
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[GitHub] [rocketmq] ni-ze commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
ni-ze commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1274193768
seems like does not matter.
sunhangda ***@***.***>于2022年4月13日 周三11:20写道：
> I do not think so.
>
> tpInfo.getSendWhichQueue().incrementAndGet()
>
> the index is a thread local variable, would change with thread.if thread
> switched, index will change.
>
> There's a mod
>
> —
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[GitHub] [rocketmq] mz0113 commented on issue #4154: maybe there is a Thread Safe problem when send a message in the 'MQFaultStrategy#selectOneMessageQueue' code
Posted by GitBox <gi...@apache.org>.
mz0113 commented on issue #4154:
URL: https://github.com/apache/rocketmq/issues/4154#issuecomment-1097686739
no, that is not my mean , you are right in some aspect,but what i want to say is messagequeue it self is a shared object , it means all threads will use the same messageQueue object, for current thread, the messageQueue with is consistent,but for other thread, it may not be consistent ,
`org.apache.rocketmq.client.impl.producer.TopicPublishInfo#selectOneMessageQueue() `
` public MessageQueue selectOneMessageQueue() {
int index = this.sendWhichQueue.getAndIncrement();
int pos = Math.abs(index) % this.messageQueueList.size();
if (pos < 0)
pos = 0;
return this.messageQueueList.get(pos);
}
`
this method will not sure it`s return value(messageQueue) is always belong to notBestBroker，so the method may be return a mq from brokerA or brokerB ,etc .for example, when this.sendWhichQueue is too big to becoming a number less than zero, the pos will be zero, and
return this.messageQueueList.get(pos); will return a messageQueue object which may not belong to notBestBroker
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