public synchronized void tearDownIfUnused() {
      if (users.get() != 0) {
        LOG.warn("Non-zero user count preventing client tear down: users=" + users.get() + " expired=" + expiredFromCache);
      }

      if (users.get() == 0 && expiredFromCache) {
        this.tearDown();
      }
    }
Attempt to tear down the client connection.
The connection will be closed if the following conditions hold:
 1. There are no active user holding the client.
 2. The client has been evicted from the cache.
metastore/src/java/org/apache/hadoop/hive/metastore/HiveClientCache.java