[libvirt] [PATCH v2 2/2] virsh: Enhance the detailed output of domblklist for networked source

[Lin Ma]

在 2015年09月04日 18:53, John Ferlan 写道:
>
> On 09/04/2015 04:26 AM, Michal Privoznik wrote:
>> On 03.09.2015 22:47, John Ferlan wrote:
>>>
>>> On 09/02/2015 11:58 AM, Michal Privoznik wrote:
>>>> From: Lin Ma <lma at suse.com>
>>>>
>>>> Format & output more detailed information about networked source
>>>>
>>>> e.g: The output without the patch:
>>>> $ virsh domblklist $DOMAIN --details
>>>> Type       Device     Target     Source
>>>> ------------------------------------------------
>>>> network    disk       vda        test-pool/image
>>>> network    disk       vdb        iqn.2015-08.org.example:sn01/0
>>>> network    disk       vdc        /image.raw
>>>> network    disk       vdd        -
>>>> network    disk       vde        -
>>>> network    disk       vdf        image1
>>>> network    disk       vdg        test-volume/image.raw
>>>>
>>>> The output with the patch:
>>>> $ virsh domblklist $DOMAIN --details
>>>> Type       Device     Target     Source
>>>> ------------------------------------------------
>>>> network    disk       vda        rbd://monitor1.example.org:6321/test-pool/image
>>>> network    disk       vdb        iscsi://192.168.124.200:3260/iqn.2015-08.org.example:sn01/0
>>>> network    disk       vdc        http://192.168.124.200:80/image.raw
>>>> network    disk       vdd        nbd+unix:///var/run/nbdsock
>>>> network    disk       vde        nbd://192.168.124.200:12345
>>>> network    disk       vdf        sheepdog://192.168.124.200:6000/image1
>>>> network    disk       vdg        gluster://192.168.124.200/test-volume/image.raw
>>> Is the goal to just format in some "standard" format or to use the
>>> format that would be used by qemu in the command line?
>> While it's the former, I think we should at least cover asses and
>> document that these strings have no special meaning and can change later
>> if we find a better way of expressing them. Or should we?
>>
> Since the Source path is provided whether or not --details is supplied,
> I guess I'd be concerned if we've ever made any "guarantees" about the
> format of the output for default displays and what a change like this
> could break. I can tell you that when there was a change to add an extra
> leading space to some display output, there were virt-tests that just
> began failing because the difference between seeing "# ..." and " # ..."
> in the output wasn't handled properly.
>
> Anyway, the man page says:
>
> Print a table showing the brief information of all block devices
> associated with I<domain>. If I<--inactive> is specified, query the
> block devices that will be used on the next boot, rather than those
> currently in use by a running domain. If I<--details> is specified,
> disk type and device value will also be printed. Other contexts
> that require a block device name (such as I<domblkinfo> or
> I<snapshot-create> for disk snapshots) will accept either target
> or unique source names printed by this command.
>
>
> Which a naive user could be led to believe that by grabbing the value in
> the "Source" column (such as "nbd://192.168.124.200:12345") they could
> feed that into "virsh domblkinfo $dom $Source" and it would work. In
> fact, someone that can write scripts better than I could be currently
> stripping that last field off and using it as input to their domblkinfo
> command in order to get the Capacity, Allocation, Physical values in
> some form. Yes, of course those would be "broken" today for network.
> Since the test environment is already set up, Lin Ma can you at least
> see what happens for the various formats if one just cut-n-pasted that
> column for domblkinfo?

For networked disks which were attached directly, domblkinfo can't 
recognize them:
virsh domblkinfo $dom $Target
will output the error message with related protocol:
"error: internal error: missing storage backend for network files using 
%s protocol"

virsh domblkinfo $dom $Source
will output "error: invalid argument: invalid path $Source not assigned 
to domain"

> One option/adjustment perhaps is we only print the "details" of the
> network source if --details is provided (and document it).  Or we could
> add something like the following after the first sentence to virsh.pod
> (for the CYA needs):
>
> For networked storage the Source displayed uses the domain XML to
> extract source protocol, transport, host name, host port, and source
> name or socket data in order to format and display in a standard manner
> starting with the protocol, such as:
>
> "$protocol[+$transport]://[$host:$port][{/$name|:$socket}]"
>
>
> That could be ugly difficult to display and I don't see any other
> current example in a quick scan through virsh.pod.
>
> John
>