Failure to create ephemeral VM when no architectures are found on the VM host

[Polona Mihalic]

MAAS version: 3.2.6
When sending post request to /MAAS/api/2.0/machines/?op=allocate, and all of the existing machines are already allocated, ephemeral machine is not created (although there is enough resources). Instead error is returned: 500 list index out of range

Traceback from regoind.log:
2022-10-27 08:13:41 maasserver: [error] ################################ Exception: list index out of range ################################
2022-10-27 08:13:41 maasserver: [error] Traceback (most recent call last):
  File "/snap/maas/23947/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/utils/views.py", line 288, in view_atomic_with_post_commit_savepoint
    return view_atomic(*args, **kwargs)
  File "/usr/lib/python3.8/contextlib.py", line 75, in inner
    return func(*args, **kwds)
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/api/support.py", line 56, in __call__
    response = super().__call__(request, *args, **kwargs)
  File "/snap/maas/23947/usr/lib/python3/dist-packages/django/views/decorators/vary.py", line 20, in inner_func
    response = func(*args, **kwargs)
  File "/snap/maas/23947/usr/lib/python3.8/dist-packages/piston3/resource.py", line 197, in __call__
    result = self.error_handler(e, request, meth, em_format)
  File "/snap/maas/23947/usr/lib/python3.8/dist-packages/piston3/resource.py", line 195, in __call__
    result = meth(request, *args, **kwargs)
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/api/support.py", line 306, in dispatch
    return function(self, request, *args, **kwargs)
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/api/machines.py", line 2546, in allocate
    ) = get_allocated_composed_machine(
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/api/machines.py", line 347, in get_allocated_composed_machine
    compose_form = ComposeMachineForPodsForm(
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/forms/pods.py", line 760, in __init__
    self.pod_forms = [
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/forms/pods.py", line 761, in <listcomp>
    ComposeMachineForm(request=self.request, data=self.data, pod=pod)
  File "/snap/maas/23947/lib/python3.8/site-packages/maasserver/forms/pods.py", line 422, in __init__
    self.initial["architecture"] = self.pod.architectures[0]
IndexError: list index out of range

[Christian Grabowski (cgrabowski)]

hmm it seems your VM Host is missing its architecture. Can you share the output of `maas $PROFILE vm-hosts read`? Additionally, was the VM Host added with "register as a KVM host" on deployment, or was this an existing host that was added to MAAS' VM Hosts?

[Polona Mihalic (polona-mihalic)]

So I checked again the architecture, and it is defined, but error still occurs. The vm host that I am working on is actually the one that has maas installed. Important info is also, that this error didn't occur when working with older maas version (I think it was 2.8), instead ephemeral machine was created as expected.

[Alexsander de Souza (alexsander-souza)]

We were not able to reproduce this on 3.2 by only requesting it to allocate a machine. We need more details about your setup:

1) what kind of KVM are you running (LXD or Virtsh) and which version?
2) is this a fresh MAAS install or have you been upgrading it since 2.x?
3) the output of `maas $PROFILE vm-hosts read`
4) the output of `maas $PROFILE machines allocate`)

[Polona Mihalic (polona-mihalic)]

So we figured it out what was the problem - we had 2 hosts, one of them was uninitialized virsh host (cores:0, memory:0):

root@maas:/home/ubuntu# maas admin machines allocate
list index out of range
root@maas:/home/ubuntu# maas admin vm-hosts read
Success.
Machine-readable output follows:
[
    {
        "default_macvlan_mode": "",
        "capabilities": [
            "composable",
            "dynamic_local_storage",
            "over_commit",
            "storage_pools"
        ],
        "host": {
            "system_id": "kwxmgm",
            "__incomplete__": true
        },
        "total": {
            "cores": 4,
            "memory": 8192,
            "local_storage": 22884122624
        },
        "storage_pools": [
            {
                "id": "default",
                "name": "default",
                "type": "zfs",
                "path": "/var/snap/lxd/common/lxd/disks/default.img",
                "total": 22884122624,
                "used": 0,
                "available": 22884122624,
                "default": true
            }
        ],
        "type": "lxd",
        "id": 1,
        "pool": {
            "name": "default",
            "description": "Default pool",
            "id": 0,
            "resource_uri": "/MAAS/api/2.0/resourcepool/0/"
        },
        "architectures": [
            "amd64/generic"
        ],
        "zone": {
            "name": "default",
            "description": "",
            "id": 1,
            "resource_uri": "/MAAS/api/2.0/zones/default/"
        },
        "memory_over_commit_ratio": 1.0,
        "available": {
            "cores": 4,
            "memory": 8192,
            "local_storage": 22884122624
        },
        "name": "crisp-skunk",
        "cpu_over_commit_ratio": 1.0,
        "used": {
            "cores": 0,
            "memory": 0,
            "local_storage": 0
        },
        "version": "5.6",
        "tags": [
            "pod-console-logging",
            "virtual"
        ],
        "resource_uri": "/MAAS/api/2.0/vm-hosts/1/"
    },
    {
        "default_macvlan_mode": null,
        "capabilities": [],
        "host": {
            "system_id": null,
            "__incomplete__": true
        },
        "total": {
            "cores": 0,
            "memory": 0,
            "local_storage": 0
        },
        "storage_pools": [],
        "type": "virsh",
        "id": 50,
        "pool": {
            "name": "default",
            "description": "Default pool",
            "id": 0,
            "resource_uri": "/MAAS/api/2.0/resourcepool/0/"
        },
        "architectures": [],
        "zone": {
            "name": "default",
            "description": "",
            "id": 1,
            "resource_uri": "/MAAS/api/2.0/zones/default/"
        },
        "memory_over_commit_ratio": 1.0,
        "available": {
            "cores": 0,
            "memory": 0,
            "local_storage": 0
        },
        "name": "sadsa",
        "cpu_over_commit_ratio": 1.0,
        "used": {
            "cores": 0,
            "memory": 0,
            "local_storage": 0
        },
        "version": "",
        "tags": [
            "pod-console-logging"
 ...