How to add a timeout to detect that an Observable didn't emit for a while

Question

My use-case is following:

I created an Observable to access a remote server to fetch some data. However there could be no response and no exception from it forever due

Answer 1

You can use timeout() operator together with retryWhen():

Observable.fromEmitter(fetchNetwork->...)
     .timeout(TIMEOUT_VALUE, TimeUnit.SECONDS)
     .retryWhen(observable -> observable.flatMap(error -> {
                if (error instanceof TimeoutException) {
                    return Observable.just(new Object());
                } else {
                    return Observable.error(error);
                }
            }))
     .subscribe(handleResult)

this will timeout the request after TIMEOUT_VALUE seconds, and will retry as long the request was timeout, other errors will be propagate as usual to the subscriber onError().