Re: [Qemu-devel] [Qemu-block] [PATCH] docs: Update preferred NBD device syntax

[John Snow <jsnow@redhat.com>]

On 9/3/19 3:02 PM, Eric Blake wrote:
> [adding libvirt list]
> 
> On 9/3/19 1:50 PM, John Snow wrote:
>>
>>
>> On 9/3/19 10:56 AM, Eric Blake wrote:
>>> Mention the preferred URI form, especially since NBD is trying to
>>> standardize that form: https://lists.debian.org/nbd/2019/06/msg00012.html
>>>
>>> Signed-off-by: Eric Blake <eblake@redhat.com>
>>> ---
>>>  qemu-doc.texi | 16 +++++++++++-----
>>>  1 file changed, 11 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/qemu-doc.texi b/qemu-doc.texi
>>> index 577d1e837640..c83fb347d77e 100644
>>> --- a/qemu-doc.texi
>>> +++ b/qemu-doc.texi
>>> @@ -297,7 +297,14 @@ qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
>>>
>>>  @item NBD
>>>  QEMU supports NBD (Network Block Devices) both using TCP protocol as well
>>> -as Unix Domain Sockets.
>>> +as Unix Domain Sockets.  With TCP, the default port is 10809.
>>>
>>> -Syntax for specifying a NBD device using TCP
>>> +Syntax for specifying a NBD device using TCP, in preferred URI form:
>>> +``nbd://<server-ip>[:<port>]/[<export>]''
>>> +
>>> +Syntax for specifying a NBD device using Unix Domain Sockets; remember
>>> +that '?' is a shell glob character and may need quoting:
>>> +``nbd+unix:///[<export>]?socket=<domain-socket>''
>>> +
>>> +Older syntax that is also recognized:
>>
>> Deprecated officially, or no?
>>
>>>  ``nbd:<server-ip>:<port>[:exportname=<export>]''
>>>
>>> -Syntax for specifying a NBD device using Unix Domain Sockets
>>>  ``nbd:unix:<domain-socket>[:exportname=<export>]''
> 
> I didn't feel like starting a deprecation clock, in part because libvirt
> is still using nbd:host:port:exportname during migration, similarly code
> in virstoragefile.c is using only the old form.  Do we want to start a
> deprecation (as a separate patch), to prod faster changes in libvirt in
> switching to the newer form where sensible?
> 

Yeah, understood -- I was merely curious for wording purposes. Some
people might wonder what "Older syntax" means and perhaps why they
shouldn't use it. It sounds like we do want to wander away from it
eventually but aren't prepared to do that yet.

I think largely such a deprecation clock is up to the workload of
whoever would have to update the libvirt workflow (You, Peter?) and how
much benefit we'd gain by dropping it in QEMU (little?)

If you don't have motivation for doing it unprompted I have little
reason to coerce you into it.

>>>
>>>  Example for TCP
>>>  @example
>>> -qemu-system-i386 --drive file=nbd:192.0.2.1:30000
>>> +qemu-system-i386 --drive file=nbd://192.0.2.1:30000
>>>  @end example
>>>
>>>  Example for Unix Domain Sockets
>>>  @example
>>> -qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket
>>> +qemu-system-i386 --drive "file=nbd+unix:///?socket=/tmp/nbd-socket"
>>>  @end example
>>>
>>>  @item SSH
>>>
>>
>> Reviewed-by: John Snow <jsnow@redhat.com>
> 
> Thanks; will queue through my NBD tree (regardless of whether we decide
> I should add more patches to start a deprecation cycle).
>