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Re: [libvirt-users] stream finish throws exception via python API



On 25.04.16 09:11, Cole Robinson wrote:
> On 04/25/2016 08:10 AM, Shahar Havivi wrote:
> > On 17.04.16 15:41, Shahar Havivi wrote:
> >> Hi,
> >> The following snippet works fine e.g. receiving the data but when calling
> >> stream.finish() we get the following error:
> >>
> >> stream = con.newStream()
> >> vol.download(stream, 0, 0, 0)
> >> buf = stream.recv(1024)
> >> stream.finish()
> >>
> >> libvirt: I/O Stream Utils error : internal error: I/O helper exited abnormally
> >> Traceback (most recent call last):
> >>   File "./helpers/kvm2ovirt", line 149, in <module>
> >>     download_volume(vol, item[1], diskno, disksitems, pksize)
> >>   File "./helpers/kvm2ovirt", line 102, in download_volume
> >>     stream.finish()
> >>   File "/usr/lib64/python2.7/site-packages/libvirt.py", line 5501, in finish
> >>     if ret == -1: raise libvirtError ('virStreamFinish() failed')
> >> libvirt.libvirtError: internal error: I/O helper exited abnormally
> >>  
> 
> The error message sucks, I'll send patches to improve it a little at least.
> 
> What's happening here is that the you haven't read all the data you requested
> (it's vol.download(path, offset, length, flags), length == 0 means read the
> whole file which I suspect you haven't done). In this case the iohelper
> program that libvirt uses won't complete feeding us all the data, and it exits
> with SIGPIPE when we close the read end of the pipe.
> 
> Now whether that should actually be an error condition is open to debate.
> virStreamFinish docs make it sound like it's legitimate to throw an error if
> it appears that all requested data wasn't read.
Thanks checking...
> 
> /**
>  * virStreamFinish:
>  * @stream: pointer to the stream object
>  *
>  * Indicate that there is no further data to be transmitted
>  * on the stream. For output streams this should be called once
>  * all data has been written. For input streams this should be
>  * called once virStreamRecv returns end-of-file.
>  *
>  * This method is a synchronization point for all asynchronous
>  * errors, so if this returns a success code the application can
>  * be sure that all data has been successfully processed.
>  *
>  * Returns 0 on success, -1 upon error
>  */
> 
> So maybe in your case you want virStreamAbort instead (which also
> unconditionally throws an error which is also an issue IMO but can be ignored)
> 
> CCing danpb for this thoughts on the erroring semantics
> 
> - Cole


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