Writing an plugin: AttributeError: module 'rest_framework.serializers' has no attribute '<Name of my serializer>'

[ziggekatten]

Netbox 3.7.4

I'm writing my first plugin, that will replace some custom scripts I've made to communicate with an external system. A bunch of coffee, and going through the tutorial when building my bare minimum plugin with one simple model, just to get to know how things connect together. So far:

• My plugin pops up in the plugin menu in the UI
• I can list data
• I can view an object
• I can add/update/delete object from nbshell
• I can view all objects as well as an single object in the REST API

However, if I try to add or edit an object in the UI, as soon as I press save, journalctl shows error:

Apr 11 12:52:28 nbdev gunicorn[2932474]: Internal Server Error: /plugins/itsm-info/itsm-instances/1/edit/
Apr 11 12:52:28 nbdev gunicorn[2932474]: Traceback (most recent call last):
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/utilities/api.py", line 39, in get_serializer_for_model
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return dynamic_import(serializer_name)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/utilities/utils.py", line 129, in dynamic_import
Apr 11 12:52:28 nbdev gunicorn[2932474]:     mod = getattr(mod, comp)
Apr 11 12:52:28 nbdev gunicorn[2932474]: AttributeError: module 'rest_framework.serializers' has no attribute 'ITSMInstanceSerializer'
Apr 11 12:52:28 nbdev gunicorn[2932474]: During handling of the above exception, another exception occurred:
Apr 11 12:52:28 nbdev gunicorn[2932474]: Traceback (most recent call last):
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/core/handlers/exception.py", line 55, in inner
Apr 11 12:52:28 nbdev gunicorn[2932474]:     response = get_response(request)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/core/handlers/base.py", line 197, in _get_response
Apr 11 12:52:28 nbdev gunicorn[2932474]:     response = wrapped_callback(request, *callback_args, **callback_kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/views/generic/base.py", line 104, in view
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return self.dispatch(request, *args, **kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/netbox/views/generic/object_views.py", line 175, in dispatch
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return super().dispatch(request, *args, **kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/netbox/views/generic/base.py", line 26, in dispatch
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return super().dispatch(request, *args, **kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/utilities/views.py", line 106, in dispatch
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return super().dispatch(request, *args, **kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/views/generic/base.py", line 143, in dispatch
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return handler(request, *args, **kwargs)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/netbox/views/generic/object_views.py", line 269, in post
Apr 11 12:52:28 nbdev gunicorn[2932474]:     obj = form.save()
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/forms/models.py", line 542, in save
Apr 11 12:52:28 nbdev gunicorn[2932474]:     self.instance.save()
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/db/models/base.py", line 814, in save
Apr 11 12:52:28 nbdev gunicorn[2932474]:     self.save_base(
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/db/models/base.py", line 892, in save_base
Apr 11 12:52:28 nbdev gunicorn[2932474]:     post_save.send(
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/dispatch/dispatcher.py", line 176, in send
Apr 11 12:52:28 nbdev gunicorn[2932474]:     return [
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox-3.7.4/venv/lib/python3.10/site-packages/django/dispatch/dispatcher.py", line 177, in <listcomp>
Apr 11 12:52:28 nbdev gunicorn[2932474]:     (receiver, receiver(signal=self, sender=sender, **named))
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/extras/signals.py", line 97, in handle_changed_object
Apr 11 12:52:28 nbdev gunicorn[2932474]:     enqueue_object(queue, instance, request.user, request.id, action)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/extras/events.py", line 68, in enqueue_object
Apr 11 12:52:28 nbdev gunicorn[2932474]:     'data': serialize_for_event(instance),
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/extras/events.py", line 29, in serialize_for_event
Apr 11 12:52:28 nbdev gunicorn[2932474]:     serializer_class = get_serializer_for_model(instance.__class__)
Apr 11 12:52:28 nbdev gunicorn[2932474]:   File "/opt/netbox/netbox/utilities/api.py", line 41, in get_serializer_for_model
Apr 11 12:52:28 nbdev gunicorn[2932474]:     raise SerializerNotFound(
Apr 11 12:52:28 nbdev gunicorn[2932474]: netbox.api.exceptions.SerializerNotFound: Could not determine serializer for nb_itsm_info.ITSMInstance with prefix ''

I have gone through my code, and I'm scratching my head here, as I clearly have an serializer in place:

from rest_framework import serializers
from ipam.api.serializers import NestedPrefixSerializer
from netbox.api.serializers import NetBoxModelSerializer, WritableNestedSerializer
from ..models import ITSMInstance

class ITSMInstanceSerializer(NetBoxModelSerializer):
    url = serializers.HyperlinkedIdentityField(
        view_name='plugins-api:nb_itsm_info-api:itsminstance-detail'
    )
    class Meta:
        model = ITSMInstance
        fields = ('id', 'url', 'display','keypath', 'baseurl', 'comments', 'environment', 'tags', 'custom_fields', 'created', 'last_updated')

[markkuleinio]

I have no idea about the exact problem but I'll try anyway:

AttributeError: module 'rest_framework.serializers' has no attribute 'ITSMInstanceSerializer'

Why would it search your custom serializer from there?

[markkuleinio]

I mean, for me it looks like some path problem. I would add some strategic print()s in get_serializer_for_model() and dynamic_import() to see if they give any insight.

[markkuleinio]

Since you say you are following the tutorial but using your own model, maybe you have missed some specific detail? Like a __init__.py somewhere? Just an idea as that causes so many strange problems in other places as well 😁

[ziggekatten]

I have gone through and compared to the tutorial, including the init.py. Can't see any differences, except my code is simpler as I have only one single model with four fields, no relations at this moment. The only thing I found sniffing in the area of my issue is: #14747 but the trick here does not help in my case.

[ziggekatten]

Further troubleshooting. Printing out the serializer_name in get_serializer_for_model() yields: nb_itsm_info.api.serializers.ITSMInstanceSerializer

Doing an import in nbshell everything seems a little bit off. I find my serializer at: nb_itsm_info.api.ITSMInstanceSerialize

Seems that my serializer ends up in an different path for some reason. The function get_serializer_for_model() itself takes an prefix argument that is empty by default.

### NetBox interactive shell (SELI148185)
### Python 3.10.12 | Django 4.2.11 | NetBox 3.7.4
### lsmodels() will show available models. Use help(<model>) for more info.
>>> import nb_itsm_info
>>> nb_itsm_info.
nb_itsm_info.NetBoxAccessListsConfig(  nb_itsm_info.config(                   nb_itsm_info.models                    nb_itsm_info.urls
nb_itsm_info.PluginConfig(             nb_itsm_info.filtersets                nb_itsm_info.navigation                nb_itsm_info.views
nb_itsm_info.api                       nb_itsm_info.forms                     nb_itsm_info.tables
>>> nb_itsm_info.api.
nb_itsm_info.api.ITSMInstance(                  nb_itsm_info.api.NestedPrefixSerializer(        nb_itsm_info.api.serializers
nb_itsm_info.api.ITSMInstanceSerializer(        nb_itsm_info.api.NetBoxModelSerializer(         nb_itsm_info.api.urls
nb_itsm_info.api.NestedITSMInstanceSerializer(  nb_itsm_info.api.WritableNestedSerializer(      nb_itsm_info.api.views
>>> nb_itsm_info.api.ITSMInstanceSerializer()
ITSMInstanceSerializer():
    id = IntegerField(label='ID', read_only=True)
    url = HyperlinkedIdentityField(view_name='plugins-api:nb_itsm_info-api:itsminstance-detail')
    display = SerializerMethodField(read_only=True)
    keypath = CharField(max_length=100)
    baseurl = URLField(max_length=100)
    comments = CharField(allow_blank=True, required=False, style={'base_template': 'textarea.html'})
    environment = ChoiceField(choices=<class 'nb_itsm_info.models.EnvironmentChoices'>, required=False)
    tags = NestedTagSerializer(many=True, required=False):
        id = IntegerField(read_only=True)
        url = HyperlinkedIdentityField(view_name='extras-api:tag-detail')
        display = SerializerMethodField(read_only=True)
        name = CharField(max_length=100, validators=[<UniqueValidator(queryset=Tag.objects.all())>])
        slug = SlugField(allow_unicode=True, max_length=100, validators=[<django.core.validators.RegexValidator object>, <UniqueValidator(queryset=Tag.objects.all())>])
        color = CharField(max_length=6, required=False, validators=[<django.core.validators.RegexValidator object>])
    custom_fields = CustomFieldsDataField(default=CreateOnlyDefault(<extras.api.customfields.CustomFieldDefaultValues object>), source='custom_field_data')
    created = DateTimeField(allow_null=True, read_only=True)
    last_updated = DateTimeField(allow_null=True, read_only=True)
>>>

[markkuleinio]

Do you still have the "import *" in __init_-.py as suggested in #14747?

[ziggekatten]

To my horror, it seems that it is as simple as my devserver needed a reboot...... so used that things reload by itself, but in this case, it needed an hard reload.... It's working now...