private static void reportTooManyInstances() {
        String resourceType = HashedWheelTimer.class.getSimpleName();
        LOG.error("You are creating too many {} instances.  {} is a shared resource that must be "
                  + "reused across the JVM, so that only a few instances are created.", resourceType, resourceType);
    }
Returns the number of pending timeouts of this {@link Timer}.
jraft-core/src/main/java/com/alipay/sofa/jraft/util/timer/HashedWheelTimer.java