[GitHub] [hadoop] fapifta commented on pull request #3579: HADOOP-17975 Fallback to simple auth does not work for a secondary DistributedFileSystem instance.

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fapifta commented on pull request #3579:
URL: https://github.com/apache/hadoop/pull/3579#issuecomment-958358986


   @symious actually the connection is not two different connection, but the same connection to the same DataNode. The problem is with what we send via the connection. In a secure environment, we are doing a SASL handshake, and for that we are sending a SASL auth header, but a DataNode expecting a single auth does not expect the SASL auth header, it expects an int with a version, and for that reads the first 4 bytes, which in the SASL auth case is 0xDEAD which translates to the first cryptic -8531 in the DN log.
   
   The setupIOStreams method works based on configuration, and server defaults coming in via the DfsClient (if I remember correctly), and the shared atomicBoolean is set to control the behaviour of the SASLDataTransferClient inside the DfsClient, so that the SASLDataTransferClient does not try to do a SASL auth, does not set a SASL header, but sends the plain request.
   
   The first client behaves correctly, but when the second client tries to connect to the DN, its shared atomicBoolean (instantiated in the DfsClient constructor) is not set before the patch, so it sends a SASL header and initiates a SASL handshake first, and fails because of the EOF it gets, as the DN closes the connection when the exception happens on its side.


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