本文主要是针对internalReleaseLease这个方法进行代码详解
/**
* Move a file that is being written to be immutable.
* @param src The filename
* @param lease The lease for the client creating the file
* @param recoveryLeaseHolder reassign lease to this holder if the last block
* needs recovery; keep current holder if null.
* @throws AlreadyBeingCreatedException if file is waiting to achieve minimal
* replication;<br>
* RecoveryInProgressException if lease recovery is in progress.<br>
* IOException in case of an error.
* @return true if file has been successfully finalized and closed or
* false if block recovery has been initiated.