Created attachment 890197 [details]
logs

*** Bug 1091858 has been marked as a duplicate of this bug. ***

What version was this tested with? I just tried to reproduce it with av7 and the following script:

---8<---
#!/usr/bin/python

import ovirtsdk.api
import ovirtsdk.xml

api = ovirtsdk.api.API(
    url='https://rhel.example.com/api',
    username='admin@internal',
    password='******',
    ca_file='/etc/pki/ovirt-engine/ca.pem',
    debug=True)

vm = api.vms.get(name="myvm")
print(vm)

vm.get_os().set_type("windows_7")
vm.update()

api.disconnect()
--->8---

And it works correctly for me.

From the failures in the ART logs it looks that this is what was sent to the engine:

<vm>
    <name>restvm_os_win</name>
    <os type="windows_7"/>
</vm>

So I also tested with the following simple shell script (no SDK in the middle):

---8<---
#!/bin/sh -x

curl \
-k \
-X PUT \
-H "Accept: application/xml" \
-H "Content-Type: application/xml" \
-d "
<vm>
<name>myvm</name>
<os type='windows_7'/>
</vm>
" \
-u admin@internal:****** \
https://rhel.example.com/ovirt-engine/api/vms/7422948b-a399-491c-9374-807306067bee
--->8---

It works fine as well.

Can you repeat the tests with the Python script and report the results?

This was run on av7. 

I reproduced it on my local environment, installed with av7.
I tried to update OS from os type="rhel_6x64" to os type="windows_7".

My versions details:
[root@dhcp163-101 ~]# rpm -qa | grep sdk
rhevm-sdk-python-3.4.1.0-1.el6ev.noarch
[root@dhcp163-101 ~]# rpm -q rhevm
rhevm-3.4.0-0.15.beta3.el6ev.noarch

Using your python script (insecure):
--------------------------------------------
#!/usr/bin/python

import ovirtsdk.api
import ovirtsdk.xml

api = ovirtsdk.api.API(
    url='https://rhel.example.com/api',
    username='admin@internal',
    password='123456',
    insecure=True,
    debug=True)

vm = api.vms.get(name="test")
print(vm)

vm.get_os().set_type("windows_7")
vm.update()

api.disconnect()
---------------------------------------------
The output is attached.

Created attachment 890784 [details]
sdk vm os type update failure reproduce output

Ilia, apparently this VM has an "vm_init" data with all fields blank or empty, and that is what is triggering this behavior. Can you check what is the content of the "vm_init" table for this VM?

  select * from vm_init where vm_guid = '61331fdb-03a3-4848-b751-7397f23a0634'

How was this VM created? From a template? Imported? Using cloud-init?

My name is Ilanit :-)

1. This VM was created from scratch, and installed with rhel
2. This vm exist in vm_init table (at the bottom):
engine=# select * from vm_init;
                vm_id                 | host_name | domain | authorized_keys | regenerate_keys | time_zone | dns_servers | dns_search_domains | networks | password | winkey | custom_script 
--------------------------------------+-----------+--------+-----------------+-----------------+-----------+-------------+--------------------+----------+----------+--------+---------------
 00000000-0000-0000-0000-000000000000 |           |        |                 | f               |           |             |                    |          |          |        | 
 90950439-143f-4a79-998e-abcb35af41a4 |           |        |                 | f               |           |             |                    | [ ]      |          |        | 
 3baa5b81-f0de-4429-9bf1-cb402dcda033 |           |        |                 |                 |           |             |                    |          |          |        | 
 3601f689-09d7-40ab-b75e-e6b72dca18dc |           |        |                 |                 |           |             |                    |          |          |        | 
 3df39d61-9075-4fe9-a86e-87ff0766b3da |           |        |                 | f               |           |             |                    | [ ]      |          |        | 
 229f5a87-e0ba-466c-b8d1-7cc61a198da0 |           |        |                 | f               |           |             |                    | [ ]      |          |        | 
 4d19341e-4dfd-4aa5-8701-5b7046df6d49 |           |        |                 | f               |           |             |                    | [ ]      |          |        | 
 5f6c6e1a-6097-4538-943c-bbcdaf2f53b7 |           |        |                 | f               |           |             |                    | [ ]      |          |        | 
 61331fdb-03a3-4848-b751-7397f23a0634 |           |        |                 |                 |           |             |                    |          |          |        | 
(9 rows)

The root cause of this problem is that the version of generateDS.py that we currently use (2.9a) doesn't handle correctly empty elements:

# cat > test.xsd <<.
<xs:schema
  version="1.0"
  xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:complexType name="Domain">
    <xs:complexContent>
      <xs:sequence>
        <xs:element name="name" type="xs:string" minOccurs="0"/>
      </xs:sequence>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="domain" type="Domain"/>

</xs:schema>
.

# cat > test.xml <<.
<domain>
  <name></name>
</domain>
.

With version 2.9a of generateDS.py the empty "name" element is removed when parsing and then rendering the XML document:

# pip install generateDS==2.9a
# generateDS.py -o test.py test.xsd
# python test.py test.xml
<?xml version="1.0" ?>
<domain/>

With version 2.12a of generateDS.py the element is preserved:

# pip install generateDS==2.12a
# generateDS.py -o test.py test.xsd
# python test.py test.xml
<?xml version="1.0" ?>
<domain>
    <name></name>
</domain>

So we need to update to version 2.12a of generateDS.py.

The version of generateDS.py has been updated. To complete the fix the SDK needs to be regenerated.

This issue has been fixed in version 3.5.0.0 of the upstream Python SDK. It will be fixed downstream with the next rebase.

*** Bug 1111128 has been marked as a duplicate of this bug. ***

This fix is contained in rhevm-sdk-python-3.5.0.0-1.el6_5, already available in brew.

Where can I download the rhevm-sdk-python-3.5.0.0-1.el6_5 package?  We have run into a similar problem when trying to update the VM description, and would like to give the new RPM a go.

*** Bug 1131932 has been marked as a duplicate of this bug. ***

To workaround the issue the caller can force an update of the domain name right before the update of the VM:

  # This is a workaround for bug 1091688, it can be removed
  # once version 3.5 of the rhevm-sdk-python package is
  # available:
  domain = vm.get_domain()
  if domain is not None and domain.get_name() is None:
    domain.set_name("")
  vm.update()

Verified on 3.4 setup av11.2, with ovirt-engine-sdk-python-3.5.0.5-1.20140820.gitc47c189.el6.noarch

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-0183.html