code: public void doProgressiveLog( StaplerRequest req, StaplerResponse rsp) throws IOException {
          AnnotatedLargeText text = obtainLog();
          if(text!=null) {
              text.doProgressText(req,rsp);
              return;
          }
          rsp.setStatus(HttpServletResponse.SC_OK);
      }
docs: Handles incremental log output.