A sample code to reproduce an issue that the unsubscription thread is sometimes different from the subscription thread.

UsingResourceSample.java

import rx.Observable;
import rx.Subscriber;
import rx.Subscription;
import rx.schedulers.Schedulers;

public class UsingResourceSample {
    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 10; i++) {
            Observable.using(() -> {
                System.out.println("Getting @" + Thread.currentThread());
                return null;
            }, Observable::just, (aVoid) -> System.out.println("Closing @" + Thread.currentThread()))
                    .subscribeOn(Schedulers.io())
                    .subscribe()
                    .unsubscribe();
        }
    }
}