我的申请必须做两件事:
这就是我实施它的方式:
public class RequestsLocker {
private volatile boolean isLocked;
public <T> Observable.Transformer<T, T> applyLocker() {
if(!isLocked()) {
return observable -> observable
.doOnSubscribe(() -> {
lockChannel();
})
.doOnUnsubscribe(() -> {
freeChannel();
});
} else {
return observable -> Observable.error(new ChannelBusyException("Channel is busy now."));
}
}
private void lockChannel() {
isLocked = true;
}
private void freeChannel() {
isLocked = false;
}
public boolean isLocked() {
return isLocked;
}
}
看起来不错。
现在我的retryWhen
实施:
public static Observable<?> retryWhenAnyIoExceptionWithDelay(Observable<? extends Throwable> observable) {
return observable.flatMap(error -> {
// For IOExceptions, we retry
if (error instanceof IOException) {
return Observable.timer(2, TimeUnit.SECONDS);
}
// For anything else, don't retry
return Observable.error(error);
});
}
我有如何使用它:
public Observable<List<QueueCarItem>> finishService(int id, PaymentType paymentType, String notes) {
return carsQueueApi.finishService(id, new FinishCarServiceRequest(paymentType.getName(), notes))
.compose(requestsLocker.applyLocker(RequestsLocker.RequestChannel.CHANGE));
}
...
public void finishCarService(QueueCarItem carItem, PaymentType paymentType,
String notes, Subscriber<List<QueueCarItem>> subscriber) {
queueApiMediator.finishService(carItem.getId(), paymentType, notes)
.subscribeOn(ioScheduler)
.observeOn(uiScheduler)
.doOnError(this::handleError)
.retryWhen(RxOperatorsHelpers::retryWhenAnyIoExceptionWithDelay)
.subscribe(subscriber);
}
doOnUnsubscribe()
调用任何错误然后锁定器的主要问题是对任何新请求打开,直到计时器到期并再次进行重新订阅。那就是问题所在。当计时器正在滴答作响时,用户可以再次提出请求。
我如何解决?
答案 0 :(得分:2)
问题在于您将变压器应用于源可观察源,即retrywhen
之前。
如果出现错误,您将始终取消订阅,然后重新订阅源可观察对象
导致doOnUnsubscribe
被调用。
我建议你试试
public Observable<List<QueueCarItem>> finishService(int id, PaymentType paymentType, String notes) {
return carsQueueApi.finishService(id, new FinishCarServiceRequest(paymentType.getName(), notes));
}
public void finishCarService(QueueCarItem carItem, PaymentType paymentType,
String notes, Subscriber<List<QueueCarItem>> subscriber) {
queueApiMediator.finishService(carItem.getId(), paymentType, notes)
.subscribeOn(ioScheduler)
.observeOn(uiScheduler)
.doOnError(this::handleError)
.retryWhen(RxOperatorsHelpers::retryWhenAnyIoExceptionWithDelay)
.compose(requestsLocker.applyLocker(RequestsLocker.RequestChannel.CHANGE));
.subscribe(subscriber);
}
PS:应用锁定器变换器看起来有点不同,即它不会在您链接的代码中使用参数。
答案 1 :(得分:1)
使用retryWhen,为了避免取消订阅onError,您必须使用 onErrorResumeNext ,它不会取消订阅。
看看这个例子
/**
* Here we can see how onErrorResumeNext works and emit an item in case that an error occur in the pipeline and an exception is propagated
*/
@Test
public void observableOnErrorResumeNext() {
Subscription subscription = Observable.just(null)
.map(Object::toString)
.doOnError(failure -> System.out.println("Error:" + failure.getCause()))
.retryWhen(errors -> errors.doOnNext(o -> count++)
.flatMap(t -> count > 3 ? Observable.error(t) : Observable.just(null)),
Schedulers.newThread())
.onErrorResumeNext(t -> {
System.out.println("Error after all retries:" + t.getCause());
return Observable.just("I save the world for extinction!");
})
.subscribe(s -> System.out.println(s));
new TestSubscriber((Observer) subscription).awaitTerminalEvent(500, TimeUnit.MILLISECONDS);
}
关于并发性,如果在flatMap运算符中执行操作,则可以指定Max concurrent。
public final <R> Observable<R> flatMap(Func1<? super T, ? extends Observable<? extends R>> func, int maxConcurrent) {
if (getClass() == ScalarSynchronousObservable.class) {
return ((ScalarSynchronousObservable<T>)this).scalarFlatMap(func);
}
return merge(map(func), maxConcurrent);
}
您可以在此处查看更多示例https://github.com/politrons/reactive
答案 2 :(得分:0)
我目前的解决方案不是在IoException上解锁RequestLocker,因为在这种情况下请求将在延迟后重复。
public <T> Observable.Transformer<T, T> applyLocker() {
if(!isLocked()) {
return observable -> observable.doOnSubscribe(() -> {
lockChannel();
}).doOnNext(obj -> {
freeChannel();
}).doOnError(throwable -> {
if(throwable instanceof IOException) {
return; // as any request will be repeated in case of IOException
}
freeChannel(channel);
});
} else {
return observable -> Observable.error(new ChannelBusyException("Channel is busy now"));
}
}