Combining timeout () with retryWhen ()
I am creating a simple application to connect to bluetooth devices using the RxAndroidBle library (Cheers Guys for a great job!). What I am experiencing is sometimes when I connect to a device I get a Gatt error with a status of 133. I know this can happen, so I want to retry everything when this error occurs. This is not a problem, I can easily do it with a statement retryWhen()
, however I have another requirement - the thread should terminate after 30 seconds if no connection has been made. I used to do this timeout()
, but the problem is when restarting the timer starts again.
So the question is how to link the timeout () statement with retryWhen (), so I can repeat some specific error, but keep counting.
I have some ideas with a concatenation of observables or some separate observables that will check the state of the connection after a wait period, but I am pondering if I can do this in a single observable.
My code looks like this:
public Observable<ConnectingViewState> connectToDevice(String macAddress) {
final RxBleDevice rxBleDevice = rxBleClient.getBleDevice(macAddress);
return rxBleDevice.establishConnection(false)
.subscribeOn(Schedulers.io())
.map(rxBleConnection -> new ConnectingViewState.ConnectedViewState(rxBleConnection))
.cast(ConnectingViewState.class)
.timeout(40, TimeUnit.SECONDS)
.startWith(new ConnectingViewState.ConnectingInProgressViewState())
.retryWhen(errors -> errors.flatMap(error -> {
if (isDefaultGattError(error)) {
return Observable.just(new Object());
} else {
return Observable.error(error);
}
}
))
.onErrorReturn(throwable -> new ConnectingViewState.ErrorState(throwable));
}
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As discussed, I wrote a test with RxJava2. The code was taken from the book "Reactive Programming with RxJava" (p. 257)
private final static int ATTEMPTS = 10;
@Test
public void name() throws Exception {
Subject<Integer> establishConnection = PublishSubject.create();
TestScheduler testScheduler = new TestScheduler();
Observable<Integer> timeout = establishConnection.
retryWhen(failures -> failures
.zipWith(Observable.range(1, ATTEMPTS), (err, attempt) ->
{
// check here for your error if(...)
if (attempt < ATTEMPTS) {
long expDelay = (long) Math.pow(2, attempt - 2);
return Observable.timer(expDelay, TimeUnit.SECONDS, testScheduler);
} else {
return Observable.error(err);
}
}
)
.flatMap(x -> x))
.timeout(30, TimeUnit.SECONDS, testScheduler)
.onErrorResumeNext(throwable -> {
if (throwable instanceof TimeoutException) {
return Observable.just(42);
}
return Observable.error(throwable);
});
TestObserver<Integer> test = timeout.test();
testScheduler.advanceTimeBy(10, TimeUnit.SECONDS);
establishConnection.onError(new IOException("Exception 1"));
testScheduler.advanceTimeBy(20, TimeUnit.SECONDS);
establishConnection.onError(new IOException("Exception 2"));
testScheduler.advanceTimeBy(31, TimeUnit.SECONDS);
test.assertValue(42);
}
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