Allow overwrites during rename. This is required for doing atomic puts. #210
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To implement atomic writes/puts, you need to write to a temporary file (non-atomic operation) and then rename the temporary file to the destination in a single (atomic) operation. Since rename does not currently support this (i.e. if the destination file already exists rename will fail and thus a delete and then rename is required, which is not atomic), added an option to pass the
renameoptions="overwrite"to the WebHDFS rename API. This is received by this code here: https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/web/resources/NamenodeWebHdfsMethods.java#L749Which in turn calls: https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java#L545
Which is documented as being atomic.
Haven't updated or run any hdfs tests - this is tested and works though in my own code base.