Fork and Join: a problem with parallel execution of two regions in spring state machine

Question

I tried to use the "fork/join" structure for the parallel execution of the state machine in the regions of state "S2". Configuration of state machine was based on uml model. And I have a problem with parallel work of these two regions. First, the state machine goes through states S20 to S23 and then pass states from S30 to S33.

Where can the problem be? Thank you in advance for your help.

This is my state machine config:

@Slf4j
@Configuration
@EnableStateMachine
public class StateMachineConfig extends StateMachineConfigurerAdapter<String, String> {

    @Override
    public void configure(StateMachineModelConfigurer<String, String> model) throws Exception {
        model
                .withModel()
                .factory(modelFactory());
    }

    @Bean
    public StateMachineModelFactory<String, String> modelFactory() {
        Resource model = new ClassPathResource("/uml/simple-forkjoin.uml");
        return new UmlStateMachineModelFactory(model);
    }


     @Override public void configure(StateMachineConfigurationConfigurer<String, String> config) throws Exception {
     config
     .withConfiguration()
     .listener(new StateMachineListener())
     .autoStartup(true);
     }
}

Example class representing the state:

@Slf4j
@WithStateMachine
public class S22 {


    @OnTransition(target = "S22")
    public void onTransition(StateContext<String, String> stateContext) {
        log.info(Colours.ANSI_BLUE + "target = \"S22\", getState().getId(): "
                + stateContext.getStateMachine().getState().getId()
                + Colours.ANSI_RESET);
        Sleep.sleep(1000);
    }

    @OnStateChanged(target = "S22")
    public void onStateChanged(StateContext<String, String> stateContext) {
        log.debug(Colours.B_HI_ANSI_GREEN + "S22 EXPECTS_ORDERS stateChanged :: Current state ID :: {}",
                stateContext.getStateMachine().getState().getId() + Colours.ANSI_RESET);
        Sleep.sleep(1000);
    }
}

logs:

2019-03-21 12:25:01.746  INFO 7648 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 8 ms
2019-03-21 12:25:01.780  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S0
2019-03-21 12:25:01.788  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S0          : target = "S0, getState().getId(): SI
2019-03-21 12:25:01.791 DEBUG 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S0          : S0 EXPECTS_ORDERS stateChanged :: Current state ID :: S0
2019-03-21 12:25:01.791  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: SI to S0
2019-03-21 12:25:01.791  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S1
2019-03-21 12:25:01.792  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S1          : target = "S1", getState().getId(): S0
2019-03-21 12:25:01.794  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S21
2019-03-21 12:25:01.794  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S21         : target = "S21", getState().getId(): S2
2019-03-21 12:25:02.795  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S22
2019-03-21 12:25:02.797  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S22         : target = "S22", getState().getId(): S2
2019-03-21 12:25:03.799  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S23
2019-03-21 12:25:03.801  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S23         : target = "S23", getState().getId(): S2
2019-03-21 12:25:04.803  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: S22 to S23
2019-03-21 12:25:04.803  INFO 7648 --- [nio-8080-exec-2] o.s.s.support.LifecycleObjectSupport     : started org.springframework.statemachine.support.DefaultStateMachineExecutor@76b2b847
2019-03-21 12:25:04.803  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : State machine started :: S2
2019-03-21 12:25:04.804  INFO 7648 --- [nio-8080-exec-2] o.s.s.support.LifecycleObjectSupport     : started S23 S22 S20 S21  / S23 / uuid=51391415-d1f5-440f-9c8e-677c00bcdd50 / id=null
2019-03-21 12:25:04.805 DEBUG 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S22         : S22 EXPECTS_ORDERS stateChanged :: Current state ID :: S2
2019-03-21 12:25:05.806  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: S21 to S22
2019-03-21 12:25:05.806 DEBUG 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S21         : S21 EXPECTS_ORDERS stateChanged :: Current state ID :: S2
2019-03-21 12:25:06.807  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: S20 to S21
2019-03-21 12:25:06.808 DEBUG 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S20         : S20 EXPECTS_ORDERS stateChanged :: Current state ID :: S2
2019-03-21 12:25:07.809  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: null to S20
2019-03-21 12:25:07.809  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S31
2019-03-21 12:25:07.810  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S31         : target = "S31", getState().getId(): S2
2019-03-21 12:25:08.211  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S32
2019-03-21 12:25:08.212  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S32         : target = "S32", getState().getId(): S2
2019-03-21 12:25:08.613  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S33
2019-03-21 12:25:08.614  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S33         : target = "S33", getState().getId(): S2
2019-03-21 12:25:09.015  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S3
2019-03-21 12:25:09.016  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S3          : target = "S3", getState().getId(): S2
2019-03-21 12:25:09.016  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : transition started! target state: S3
2019-03-21 12:25:09.017  INFO 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S3          : target = "S3", getState().getId(): S2
2019-03-21 12:25:09.018  INFO 7648 --- [nio-8080-exec-2] o.s.s.support.LifecycleObjectSupport     : stopped org.springframework.statemachine.support.DefaultStateMachineExecutor@76b2b847
2019-03-21 12:25:09.018  INFO 7648 --- [nio-8080-exec-2] o.s.s.support.LifecycleObjectSupport     : stopped S23 S22 S20 S21  /  / uuid=51391415-d1f5-440f-9c8e-677c00bcdd50 / id=null
2019-03-21 12:25:09.019 DEBUG 7648 --- [nio-8080-exec-2] com.fj.forkJointest.forkJoin.S4          : S4 EXPECTS_ORDERS stateChanged :: Current state ID :: S4
2019-03-21 12:25:09.020  INFO 7648 --- [nio-8080-exec-2] c.f.f.config.StateMachineListener        : state changed from: S2 to S4

This is my github project

score 0 · Answer 1 · answered Mar 22 '19 at 09:41

0

Spring State Machine uses TaskExecutor for region executions and by default it's synchronous. To achieve async execution you need to override the default task executor.

You can do it in a couple of ways:

Using the StateMachineConfigurationConfigurer:

@Override
public void configure(StateMachineConfigurationConfigurer<States, Events> config) throws Exception {
    config
        .withConfiguration()
            //other configs
            .taskExecutor(myAsyncTaskExecutor())
}

public TaskExecutor myAsyncTaskExecutor() {
    ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
    taskExecutor.setCorePoolSize(5);
    return taskExecutor;
}

Or simply declaring a bean, which will be auto-picked up from SM:

@Bean(name = StateMachineSystemConstants.TASK_EXECUTOR_BEAN_NAME)
public TaskExecutor taskExecutor() {
    ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
    taskExecutor.setCorePoolSize(5);
    return taskExecutor;
}

answered Mar 22 '19 at 09:41

hovanessyan

30,580
6
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83

Thank You Hovanessyan, Your method worked by declaring Bean. But only when I changed the Fork structure in UML. Instead of two arrows pointing two machines ( [UML not working](https://i.stack.imgur.com/9p9n2.jpg) ) I used one ([UML working](https://i.stack.imgur.com/uqDtF.jpg) ) indicating the state S2 that has them. Otherwise, everything is executed on the same thread (eTaskExecutor-3) except for the SI state initiating the main state machine (eTaskExecutor-1). Your first option caused an error: ...Error creating bean with name 'stateMachine': ... ThreadPoolTaskExecutor not initialized – Brutus Mar 25 '19 at 09:42
What can the problem be? – Brutus Mar 25 '19 at 09:43
@Brutus just follow the official example for fork/join and adopt accordingly to your case https://docs.spring.io/autorepo/docs/spring-statemachine/1.2.x-SNAPSHOT/reference/html/statemachine-examples-tasks.html Also if the answer solved your problem, consider accepting it so that others can see it solves the issue described in the question – hovanessyan Mar 25 '19 at 09:50
@Brutus I tried changing the UML as you have mentioned, but it does not run for me. – Ankur Singhal Jul 15 '20 at 14:40

score 0 · Answer 2 · answered Jul 15 '20 at 14:38

Executor needs to be defined as below

public TaskExecutor myAsyncTaskExecutor() {
            ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
            taskExecutor.setCorePoolSize(5);
            taskExecutor.initialize();
            return taskExecutor;
        }

State Machine Configuration

.taskExecutor(myAsyncTaskExecutor()).taskScheduler(new ConcurrentTaskScheduler())

Fork and Join: a problem with parallel execution of two regions in spring state machine

2 Answers2