code: public void stop() {
          if (log.isDebugEnabled()) {
              log.debug("stop");
          }
          try {
              engine.stop();
          } catch (IllegalStateException e) {
              if (log.isTraceEnabled()) {
                  log.warn("stop caught an IllegalStateException", e);
              } else if (log.isDebugEnabled()) {
                  log.debug("stop caught an IllegalStateException");
              }
          }
      }
docs: {@inheritDoc}