[paramiko] Paramiko connection does not react well to sync

[Robey Pointer]

On 24 Jul 2007, at 8:59, Matthews, James wrote:

> Greetings,
>
>             I have been furiously testing a Python (v2.4.3)  
> application built on wx.Python (v) that uses paramiko (v1.7) for an  
> SSH connection to essentially a “bare-bones” Linux box running  
> dropbear (v0.49).  The setup was working great except for one  
> annoying bug that kept popping up in different locations.  Namely,  
> it appears to happen in very random places during a very long  
> process in which the application connects to the Linux box, moves a  
> few files around, updates the image on the box, and then mounts two  
> particular partitions to restore some files (namely for convenience  
> so I don’t have to do it manually after the image update).  Now the  
> problem appeared after somebody else went in and added some lines  
> of code which they thought would make this process more reliable.   
> I don’t know if this is exactly what was causing the problem, but  
> after weeks of debugging, tracing, and cursing I found what I  
> believe the problem to be.  Apparently, they had added a function  
> to open a new session to execute a Linux command on the box, which  
> just so happened to be the ‘sync’ command.  They had put this in  
> after every time I mounted a partition in order to access it, and  
> their comments said something along the lines of, “#Make sure the  
> File System is aware”, or “#Give the File System time before  
> accessing the file”.  It seems that around this command in the  
> code, the 10 second connection check would sense a downed connection.
>
>             I’m sorry for the length of this email, but basically  
> my question is… Is it even necessary to perform a ‘sync’ operation  
> after just a simple partition mount?  And further more, would it  
> make any sense for this to cause paramiko to close the Transport  
> unexpectedly?

Sorry for the late reply; I've been on vacation.

I can't think of a reason why a 'sync' would cause paramiko to  
disconnect.  But I also don't think it's necessary.  The 'mount'  
command should not complete until the filesystem is mounted.  Maybe  
someone else can correct me if I'm wrong.

robey