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https://issues.apache.org/jira/browse/ROCKETMQ-107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15882156#comment-15882156
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ASF GitHub Bot commented on ROCKETMQ-107:
-----------------------------------------
Github user shroman commented on the issue:
https://github.com/apache/incubator-rocketmq/pull/68
I also think that using `synchronized` fits well here.
But I would do it in the following way:
1. Make `serviceState` volatile
```java
private volatile ServiceState serviceState;
```
2. Synchronize only blocks that needs to be atomic (possibly making
synchronized methods -- current huge `start` chunk of code doesn't look nice)
And, of course, provide comments to public methods ;)
> Access ServiceState is not thread safe when start() or shutdown()
> -----------------------------------------------------------------
>
> Key: ROCKETMQ-107
> URL: https://issues.apache.org/jira/browse/ROCKETMQ-107
> Project: Apache RocketMQ
> Issue Type: Bug
> Components: rocketmq-client
> Reporter: Jaskey Lam
> Assignee: Jaskey Lam
> Priority: Minor
>
> When start() or shutdown(), service's state is not thread safe which may
> break happen-before.
> For example:
> {code}
> switch (this.serviceState) {
> case CREATE_JUST:
> log.info("the consumer [{}] start beginning. messageModel={},
> isUnitMode={}", this.defaultMQPushConsumer.getConsumerGroup(),
> this.defaultMQPushConsumer.getMessageModel(),
> this.defaultMQPushConsumer.isUnitMode());
> this.serviceState = ServiceState.START_FAILED;
> ..// do some start job here
> this.serviceState = ServiceState.RUNNING;
> break;
> case RUNNING:
> case START_FAILED:
> case SHUTDOWN_ALREADY:
> throw new MQClientException("The PushConsumer service state
> not OK, maybe started once, "//
> + this.serviceState//
> + FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK),
> null);
> default:
> break;
> }
> {code}
> 1. If the user is start twice in two thread, the resources may initize twice.
> 2. if the user start in threadA and shutdown very quicky in another thread B,
> shutdown may not reclaim the resources.
> Though the sceniro is very uncommon, but it is indeed a bug here. Fix is
> actually quite trivial.
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