code: public void shutdown() {
          if (state != null) {
              for (HystrixRequestVariableDefault<?> v : state.keySet()) {
                  // for each RequestVariable we call 'remove' which performs the shutdown logic
                  try {
                      HystrixRequestVariableDefault.remove(this, v);
                  } catch (Throwable t) {
                      HystrixRequestVariableDefault.logger.error("Error in shutdown, will continue with shutdown of other variables", t);
                  }
              }
              // null out so it can be garbage collected even if the containing object is still
              // being held in ThreadLocals on threads that weren't cleaned up
              state = null;
          }
      }
docs: Shutdown {@link HystrixRequestVariableDefault} objects in this context.
  <p>
  <b>NOTE: This must be called if <code>initializeContext()</code> was called or a memory leak will occur.</b>