api/metrics-api-jaxrs/src/main/java/org/hawkular/metrics/api/servlet/rx/ObservableServlet.java
public static Observable<Void> create(final ServletOutputStream out) {
        return Observable.unsafeCreate(subscriber -> {
            final ServletWriteListener listener = new ServletWriteListener(subscriber, out);
            out.setWriteListener(listener);
        });
    }
public static Observable<Void> create(final ServletOutputStream out) {
        return Observable.unsafeCreate(subscriber -> {
            final ServletWriteListener listener = new ServletWriteListener(subscriber, out);
            out.setWriteListener(listener);
        });
    }
Observes {@link ServletOutputStream}.

<p>
This method uses Servlet 3.1 non-blocking API callback mechanisms. When the
container notifies that HTTP response can be written, the subscribed
{@code Observer}'s {@link Observer#onNext onNext} method is invoked.

<p>
Before calling this method, a web application must put the corresponding HTTP
request into asynchronous mode.

@param out servlet output stream
@return Observable of HTTP response write ready events