【BUG】use HystrixTimer execute fallback will cause fallback execute twice?

[Yaccc]

Because hystrixtimer and workerThread do not synchronize, this can cause this problem!

when run() method throw a exception,workerThread will execute the fallback() method.

import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandProperties;
import rx.Observable;
import rx.Subscriber;
import java.io.IOException;

public class HystrixUse extends HystrixCommand<String> {
   public static ThreadLocal<String> threadLocal=new ThreadLocal<>();
    private String name;

    public HystrixUse(String name) {
        super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("Semaphore Echo"))
                .andCommandKey(HystrixCommandKey.Factory.asKey("Echo"))
                .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                        .withExecutionIsolationStrategy(HystrixCommandProperties.ExecutionIsolationStrategy.THREAD)
                        .withExecutionIsolationSemaphoreMaxConcurrentRequests(2).withExecutionIsolationThreadTimeoutInMilliseconds(2000)
                .withExecutionIsolationThreadInterruptOnTimeout(true).withFallbackIsolationSemaphoreMaxConcurrentRequests(1)));
        this.name = name;

    }

    @Override
    protected String run() throws Exception {

        int [] a=new int[5];
        System.out.println("execute run");
        //cause  exception
        int i = a[6];
        return "hello" + name;
    }

    @Override
    protected String getFallback() {
        System.out.println("execute -fallback"+Thread.currentThread());

        return "fallback";
    }

    public static void main(String[] args) {

        HystrixUse hystrixUse=new HystrixUse("nn");
        Observable<String> stringObservable = hystrixUse.toObservable();
        stringObservable.subscribe(new Subscriber<String>() {
            @Override
            public void onCompleted() {
                System.out.println("completed");
            }

            @Override
            public void onError(Throwable e) {
                System.out.println(e);
            }

            @Override
            public void onNext(String s) {
                System.out.println(s);
            }
        });

        try {
            System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

when execute run，use a breakpoint hang the workerThread on HystrixCommond object ,then wait time is timeout.the HystrixTimer will execute fallback.the result is as follows

execute run
execute -fallbackThread[hystrix-Semaphore Echo-1,5,main]
execute -fallbackThread[HystrixTimer-1,5,main]
fallback
completed

fallback method execute twice, this is a bug? or other reasons

my version is 1.3.16

[mattrjacobs]

Executing the fallback twice is definitely a bug. Are you able to upgrade to the latest Hystrix (or even something in the 1.4.x series) and see if the bug occurs there?

[Yaccc]

@mattrjacobs I can't find pull request in CHANGELOG. can you give me a bugfixed version? thank you very much!!

[mattrjacobs]

I'm not sure what you're looking for. Many things have changed since 1.3.16 - that's at least 3 years old. If you have a reliable way of reproducing your issue in 1.3.16, it would be great to know if you an repro it in a newer version.

[Yaccc]

i'm a member of Base component team , Many business R & D teams use our components,I have to make sure a hystrix version is available.In this case, I can only test each version.

Thank you for your reply!