[paramiko] closing SFTP connections

[Robey Pointer]

On 10 Dec 2006, at 16:53, Michael Gratton wrote:

> Hi guys,
>
> We're using Paramiko for some SFTP transfers and are occasionally  
> seeing
> connections not getting closed down correctly. This results in the
> python process seeming to hang. After doing an strace/lsof on such a
> process, it is continually select'ing an SSH connection.
>
> We are closing the connection by calling SFTPClient.close. Looking
> through the code base it seems that this calls Channel.close but not
> Transport.close.
>
> I'm going to try to work around the problem by calling Transport.close
> explicitly after closing the client, but is this something that should
> happen in SFTPClient.close automatically?

An SSH transport can host more than one open channel at a time.  For  
example, you could have two open SFTP sessions and a shell session  
all over the same transport.  So having Channel or SFTPClient close  
the Transport might prematurely close other sessions.

(I think we used to have a __del__ method on Transport, that would  
automatically close itself if it was garbage-collected, but python  
interacts badly with __del__ in many cases and I think we decided it  
was safer to not have it.)

Since all Channel and SFTPClient objects belong to a single  
Transport, if you close the Transport (or SSHClient), it should  
automatically close all of its channels.  That will let you still  
have only one "close()" call.

Hope that helps1
robey