Scheduling Page Requests example code

SchedulingPageRequests.java

// This function takes a page, which defines the limit and offset
// and makes the web service call using that limit/offset
Function<RequestPager.Page, List<MyObject>> function = (page) -> {
    try {
        return service.someApiCall(page.getLimit(), page.getOffset())
                .get(timeout.toMillis(), TimeUnit.MILLISECONDS);
    } catch (Exception e) {
        throw new RuntimeException("A page request failed", e);
    }
};

// You'll need to know how many objects you're trying to retrieve.
// I'm assuming you have an API call to return this count.
int expectedCount = service.countMyObjects();

// define our parameters
int pageSize = 50;
int retryAttempts = 2
int threadCount = 3      // Number of simultaneous REST calls

// -- 1. Create a new Request pager
RequestPager<List<MyObject>> pager = new RequestPager<>(function, retryAttempts, threadCount);

// -- 2. Here we generate a runner which has our Supplier queue, ExecutorService and 
//       the Observable we subscribe to to consume the web service return values
RequestPager.Runner<List<MyObject>> runner = pager.build(expectedCount, pageSize);

// -- 3. We get the observable from the runner and set up our subscribers
Observable<List<MyObject>> observable = runner.getObservable();
observable.subscribeOn(Schedulers.io())
    .subscribe(xs -> System.out.println("Retrieved " xs.size() + " objects"),
               ex -> System.err.println("Bummer ... Exception was thrown"),
               () -> System.out.println("All page requests were completed"));

// -- 4. Start fetching data
runner.run()