While using django restframework Multiple database, serializer.is_valid() always go to default database for validation

Question

I am using django restframework and want to handle multiple databases. I am using django function using(alias) and switch_db(alias) for manually switching between database whenever I want to Get, Post or update data.

I am facing problem while posting and updating data.i.e whenever serializer.is_valid() will be called.

serializer.is_valid() will go and first check for db_alias in model.py file. If I have not specified db_alias under meta it will select default database for validation. If I am specifying db_alias in model it will select that database for validation.

But I do not want to specify db_alias in model since my usecase is to store data on different database based on some logic in my view file. So dynamically I want to select database from view and want to store data in it.

Almost I have implemented but I am facing problem when my model is having Reference Field. In this case serializer.is_valid is going to default database for validating that reference field.

Required Details: I am using mongoengine(0.9.0), document, document serializer.

My files are as below:

model.py:

class ngroup(Document):

    groupname = StringField(max_length=100, required=True)
    description = StringField(max_length=100, required=False)
    parent = ReferenceField('ngroup',null=True)
    created_ts = DateTimeField(default=datetime.now())
    modified_ts = DateTimeField(default=datetime.now())
    is_deleted = BooleanField(default=False)

serializer.py:

from device_management.models import ngroup
from rest_framework_mongoengine.serializers import DocumentSerializer
from mongoengine import EmbeddedDocumentField, ReferenceField, StringField, ObjectIdField, IntField, BooleanField, FloatField, DateTimeField,ListField


class ngroupSerializer(DocumentSerializer):

    class Meta:
        model = ngroup

    def setOrgId(self, orgid):
        self.orgid = orgid

    def create(self, validated_data):
        ngroup_data = ngroup(**validated_data).switch_db(self.orgid)
        ngroup_data.save()
        return ngroup_data

    def update(self, instance, validated_data):
        ngroup_data = ngroup.objects.using(self.orgid).get(id = instance.id)
        ngroup_data = ngroup_data.switch_db(self.orgid)
        ngroup_data = ngroup_data.update(**validated_data)
        return validated_data

    def to_internal_value(self, data):
        print "data:" , data
        return super(DocumentSerializer, self).to_internal_value(data)  

view.py:

def create(self, request, format=None):
    orgid = str(request.user.orgid.id)
    data=request.data

    serializer = ngroupSerializer(data=data)
    if serializer.is_valid():
        try:
            serializer.save()
        except Exception as e:
            log.error("create" , extra={'extra':{'error': str(e),'message' :strings.DATA_VALIDATION_ERROR }})
            return response.errorResponse(message=strings.SERIALIZATION_ERROR_MSG,error=str(e),rstatus=status.HTTP_400_BAD_REQUEST)
        return response.successResponse(res_data=serializer.data, message=strings.POST_SUCCESS_MSG, rstatus=status.HTTP_201_CREATED)
    log.error("create" , extra={'extra':{'error': serializer.errors,'message' :strings.DATA_VALIDATION_ERROR }})
    return response.errorResponse(message=strings.DATA_VALIDATION_ERROR,error=serializer.errors,rstatus=status.HTTP_400_BAD_REQUEST)

settings.py:

DATABASES = {
     'default': {
        'ENGINE': 'django_mongodb_engine',
        'NAME': 'mydb',
        'USER': 'admin',
        'PASSWORD':'admin123',
        'HOST': '127.0.0.1',
        'PORT': 27017,
        'DBTYPE' : "mongo",
    },
    '586e47c784413825f2b5bc49': {
        'ENGINE': 'django_mongodb_engine',
        'NAME': 'mydb1',
        'USER': 'admin',
        'PASSWORD':'admin123',
        'HOST': '127.0.0.1',
        'PORT': 27017,
        'DBTYPE' : "mongo",
    },
    # Enter super_user organisation here. This DB will be same as default db only always
    '58996fb28441384430dc8ae6': {
        'ENGINE': 'django_mongodb_engine',
        'NAME': 'mydb',
        'USER': 'admin',
        'PASSWORD':'admin123',
        'HOST': '127.0.0.1',
        'PORT': 27017,
        'DBTYPE' : "mongo",
    },
}

pip freeze(Installation versions):

Django==1.5.11
django-browserid==2.0.2
django-classy-tags==0.8.0
django-missing==0.1.18
django-mongo-auth==0.1.3
django-mongodb-engine==0.6.0
django-mongoengine==0.2.1
django-redis-sessions==0.5.6
django-rest-framework-mongoengine==3.3.0
django-sekizai==0.10.0
django-websocket-redis==0.4.7
djangorestframework==3.1.2
djangorestframework-jwt==1.9.0
djangotoolbox==1.8.0
gevent==1.1.2
greenlet==0.4.10
httplib2==0.9.2
mongoengine==0.9.0
oauthlib==2.0.1
pika==0.10.0
Pygments==2.1.3
PyJWT==1.4.2
pymongo==2.8
python-dateutil==2.6.0
python-openid==2.2.5
pytz==2016.10
redis==2.10.5
requests==2.12.3
requests-oauthlib==0.7.0
rest-condition==1.0.3
six==1.10.0
tweepy==3.5.0
twilio==5.7.0

I have overide create in serializer to take care of database while calling serializer.save() but how to handle serializer.is_valid().

My project has been stuck at this point. Any help will be greatly appreciated...

Answer 1

This is not the exact solution to above problem but we have 2 options.

1) Do not go for serializer.is_valid() or serializer.save(). Directly create ngroup:

def my_create(self, validated_data):
    gateway = Gateway(**validated_data).switch_db(self.orgid)
    gateway.save()
    return gateway

2) Another solution is to use django-mogodb-engine and django models and modelserializers instead of documents and documents serializers.

I have tried following this with Django-mongodb-engine and are working well:

-> JWT authentication
-> custom user
-> foreign key
-> embedded model
-> list of embedded model
-> dict field
-> **Routers for switching between databases.(Manual switching DB is not required)**

I can also use middleware_classes to specify runtime in each request which database to use. Reference Link: Django Authenticate Backend Multiple Databases