[ROCKETMQ-107] Access ServiceState is not thread safe when start() or shutdown()

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 4.0.0-incubating
• Fix Version/s: 4.1.0-incubating
• Component/s: rocketmq-client
• Assignee: Jaskey Lam
• Reporter: Jaskey Lam
• Created: 21/Feb/17 08:08
• Updated: 20/Apr/17 07:10
• Resolved: 20/Apr/17 07:10

Description

When start() or shutdown(), service's state is not thread safe which may break happen-before.

For example:

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;
        }

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.

Issue Links

• links to: GitHub Pull Request #68