Fails to compose KVM machine with storage from disk pool

[Brett Milford]

When composing a VM which contains storage from a virsh 'disk' pool Maas fails with the following:

(/var/snap/maas/common/log/regiond.log
2020-03-27 04:29:43 maasserver.websockets.protocol: [critical] Error on request (40) pod.compose: Pod unable to compose machine: Unable to compose machine because: Failed talking to pod: Start t
ag expected, '<' not found, line 1, column 1 (<string>, line 1)
        Traceback (most recent call last):
          File "/snap/maas/5177/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1442, in gotResult
            _inlineCallbacks(r, g, deferred)
          File "/snap/maas/5177/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1432, in _inlineCallbacks
            deferred.errback()
          File "/snap/maas/5177/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 500, in errback
            self._startRunCallbacks(fail)
          File "/snap/maas/5177/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 567, in _startRunCallbacks
            self._runCallbacks()
        --- <exception caught here> ---
          File "/snap/maas/5177/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 653, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "/snap/maas/5177/lib/python3.6/site-packages/maasserver/websockets/handlers/pod.py", line 384, in wrap_errors
            "Pod unable to compose machine: %s" % str(failure.value)
        maasserver.exceptions.PodProblem: Pod unable to compose machine: Unable to compose machine because: Failed talking to pod: Start tag expected, '<' not found, line 1, column 1 (<string>,
line 1)

Happens with Maas version 2.7 snap and ppa packaged versions.

Steps to recreate:
1) setup Maas with a kvm pod.
2) define a diskpool on the hypervisor
cat <<EOF> sdb-pool.xml
<pool type="disk">
  <name>sdb</name>
  <source>
    <device path='/dev/sdb'/>
    <format type='gpt' />
  </source>
  <target>
    <path>/dev</path>
  </target>
</pool>
EOF
virsh pool-define sdb-pool.xml
virsh pool-start sdb

3) Compose a VM with storage from the sdb pool.

[Brett Milford (brettmilford)]

Same error occurs when using a zfs pool.

[Alberto Donato (ack)]

With a similar configuration, this is the error I get from virsh when composing the VM from MAAS:

        provisioningserver.drivers.pod.virsh.VirshError: Virsh command ['vol-create-as', 'loop29', '15f71b1f-76b3-47f7-adbb-d87852d22f77', '1000000000', '--allocation', '0', '--format', 'raw'] failed: Failed to create vol 15f71b1f-76b3-47f7-adbb-d87852d22f77
        error: unsupported configuration: unknown volume format type raw

[Alberto Donato (ack)]

note that currently "disk"-backed pools are not supported in MAAS.

[Alberto Donato (ack)]

@Brett the zfs issue is likely different, if you can reproduce it consistently could you please open a separate bug with details on how to do it?

[Seyeong Kim (seyeongkim)]

Please refer to https://bugs.launchpad.net/maas/+bug/1921658 as well

pexpect cmd and result.. for FYI

May 31 07:53:14 xtrusia sh[27020]: 2021-05-31 07:53:14 stdout: [info] Seyeong pexpect.send() : b'vol-path 9d2217b0-4433-48a7-9be9-32dc8552c498 --pool maas_guest_lvm_vg
' 41
May 31 07:53:14 xtrusia maas.drivers.pod.virsh: [info] Seyeong run : [' ', '<433-48a7-9be9-32dc8552c498 --pool maas_guest_lvm_vg', '/dev/maas_data_vg/9d2217b0-4433-48a7-9be9-32dc8552c498', '']

pexpect should return only /dev/maas_data_vg/9d2217b0-4433-48a7-9be9-32dc8552c498 but it includes part of command as well

I built python 3.6.12 3.7.10 3.8.10 as well and run maas, but there are the same issue.

[Seyeong Kim (seyeongkim)]

I tested later version of python (below) with maas 2.8.4

1. Python 3.6.12
2. Python 3.7.10
3. Python 3.8.10

but the symptom is the same

[Seyeong Kim (seyeongkim)]

I tested anther thing.

I changed libreadline from 7 to 8 ( in addition to this, I needed to add libtinfo.so.6 as well, as a dependent lib )

I'm able to compose kvm host.

I'll confirm this again