// putIfAbsent lifespan only
      f = c.putAsync("k", "v3");
      assertNull(f.get());
      f = c.putIfAbsentAsync("k", "v4", 1000, TimeUnit.MILLISECONDS);
      markStartTime();
      assert f != null;
      assert !f.isCancelled();
      assertEquals("v3", f.get()); //here's the problem!!