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From "Goldstein Lyor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SSHD-936) Track SFTP put successful completion
Date Thu, 01 Aug 2019 15:52:00 GMT

    [ https://issues.apache.org/jira/browse/SSHD-936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16898166#comment-16898166
] 

Goldstein Lyor commented on SSHD-936:
-------------------------------------

There is no such operation called "put" in the SFTP protocol - what the command does is OPEN
+ n * WRITE + CLOSE - all of them reflected by the {{SftpEventListener}}. Furthermore, surprisingly,
there is such thing as a "successful" or "aborted" state of  a file transfer. There is no
indication to the server how many bytes the client intends to write so there is no way to
"track" the upload. The client might decide to close the transfer after having written only
part of  the file due to some client-side reasons - the server will simply see the same OPEN+WRITE+CLOSE
sequence as if the full file was transferred (less WRITE(s) of course). Furthermore, there
is no "close reason code" to tell the server that this transfer has been aborted. Furthermore,
the client might decide to send *more* than the actual file size (by re-sending the same block
of data several times) and even send the data "out-of-sequence" - i.e., write block 100 before
block 99.

I believe I have seen this request in the past and pretty much gave the same answer - if you
want an all-or-nothing indication then SCP and SFTP is the way - in SCP the client tells the
server how many bytes are going to be uploaded, and the server makes sure that *exact* number
of bytes is sent. You can use an {{ScpTransferEventListener}} to monitor such transfers.

> Track SFTP put successful completion
> ------------------------------------
>
>                 Key: SSHD-936
>                 URL: https://issues.apache.org/jira/browse/SSHD-936
>             Project: MINA SSHD
>          Issue Type: Wish
>    Affects Versions: 2.1.0
>            Reporter: Logan
>            Priority: Major
>
> While we can track sftp events with SftpEventListener, there is no event/hook to indicate
the sftp put is completed successfully. "Successfully" here means file transfer was done
without being terminated/aborted for various reasons (user intentional termination, broken
connection because of network error....). I think this was tried in earlier versions through
[FileUploadAware|[https://github.com/apache/mina-sshd/pull/11/files]]. Is this something possible
or just a limitation of protocol?
>  
> FYI - close method of SftpEventListener is called for successfully transfers as well
as aborted connections.



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