Django DB router, not working with 2 different databases (mySQL, PostgreSQL)

Question

local_oleg.py:

from local import *  # noqa

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'schema1',
        'USER': 'postgres',
        'PASSWORD': 'zazaking',
        'HOST': 'localhost',
        # 'PORT': '',
        # 'OPTIONS': {'autocommit': True},
    },
    'legacy': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'legact_db',
        'USER': 'root',
        'HOST': '127.0.0.1',
        'PASSWORD': '',
    }

}

DATABASE_ROUTERS = ['.integrationRouter']

integrationRouter.py:

class integrationRouter(object): 
    import ipdb; ipdb.set__trace();
    def db_for_read(self, model, **hints):
        "Read from legace db if the model = 'integration'"
        if model._meta.app_label == 'integration':
            return 'legacy'
        return 'default'

    def db_for_write(self, model, **hints):
        "Write db is always default db"
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        "Allow any relation if a both models in integration app"
        if obj1._meta.app_label == 'integration' and obj2._meta.app_label == 'integration':
            return True
        # Allow if neither is integration app
        elif 'integration' not in [obj1._meta.app_label, obj2._meta.app_label]: 
            return True
        return False#Don't allow relatioin between legacy and default dchemas

    def allow_syncdb(self, db, model):
        if db == 'legacy' or model._meta.app_label == "integration":
            return False # we're not using syncdb on our legacy database
        else: # but all other models/databases are fine
            return True

Running: python manage.py shell_plus --settings=settings.local_oleg

In the shell:

>>> a = Users.objects.all()
>>> a
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/models/query.py", line 71, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/models/query.py", line 96, in __iter__
    self._fetch_all()
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/models/query.py", line 854, in _fetch_all
    self._result_cache = list(self.iterator())
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/models/query.py", line 166, in iterator
    if connections[self.db].features.supports_select_related:
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/models/query.py", line 817, in db
    return self._db or router.db_for_read(self.model)
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/utils.py", line 239, in _route_db
    for router in self.routers:
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/utils/functional.py", line 49, in __get__
    res = instance.__dict__[self.func.__name__] = self.func(instance)
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/db/utils.py", line 230, in routers
    router = import_by_path(r)()
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/utils/module_loading.py", line 21, in import_by_path
    module = import_module(module_path)
  File "/home/oleg/.virtualenvs/tomigo_core/local/lib/python2.7/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
ValueError: Empty module name

While if I define the mySQL database as a single, default database, everything works fine.

Can post the user model if necessary, although I don't thin that it is relevant.

I'm not sure routers can be referenced by relative module name, try using the fully-qualified module name in DATABASE_ROUTERS — lanzz
– lanzz, Commented Feb 6, 2014 at 12:35
Moved the router into the legacy app, and changed the path to legacy.integrationRouter, and got a different error, updated the post. — Oleg Belousov
– Oleg Belousov, Commented Feb 6, 2014 at 12:49
If your module file is legacy/integrationRouter.py, and your class name is integrationRouter, then your setting should be DATABASE_ROUTERS = ['legacy.integrationRouter.integrationRouter']; or alternatively, you can add a from .integrationRouter import integrationRouter line to your legacy/__init__.py file. — lanzz
– lanzz, Commented Feb 6, 2014 at 12:52
raise ValueError("fallback required, but not specified")ValueError: fallback required, but not specified :( — Oleg Belousov
– Oleg Belousov, Commented Feb 6, 2014 at 12:58

lanzz · Accepted Answer · 2014-02-06 13:08:38Z

1

DATABASE_ROUTERS = ['.integrationRouter']

The DATABASE_ROUTERS setting cannot reference relative module names. Replace your setting with a fully-qualified module and class name.

answered Feb 6, 2014 at 13:08

lanzz

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