DB Router default issue

[JJ Zolper]

Hello, I am trying to prevent models in my api app from migrating into the default database but I'm confused about the router. It seems every time I run migrate even with the router it continues to migrate.

#apps.py

from django.apps import AppConfig

class ApiConfig(AppConfig):
    name = 'api'
    label = 'api'

#settings.py

DATABASE_ROUTERS = ['myproject.dev_db_router.APIRouter',]

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'default.sqlite3'),
    },
    'mydb': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'mydb.sqlite3'),
    },
}

#dev_db_router.py

class APIRouter:
    """
    A router to control all database operations on models in the
    api application.
    """
    route_app_labels = {'api',}

    def db_for_read(self, model, **hints):
        """
        Attempts to read api models go to mydb.
        """
        if model._meta.app_label in self.route_app_labels:
            return 'mydb'
        return False

    def db_for_write(self, model, **hints):
        """
        Attempts to write api models goes to mydb.
        """
        if model._meta.app_label in self.route_app_labels:
            return 'mydb'
        return False

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the api app only appears in the
        'mydb' database.
        """
        if app_label in self.route_app_labels:
            return db == 'mydb'
        return False

I've tried:
python manage.py migrate --database=default
python manage.py migrate

etc and every time it says:
  Applying api.0001_initial... OK

Even though I told it False if it does not meet the case of db == 'mydb'. I can specify 'mydb' and it says it works:
python manage.py migrate --database=mydb
but my concern is it always migrates into default even when I'm trying to tell it not to. In the future there will be models I do want to migrate into default, but not these in the api app. Based on the documentation I'm doing everything correctly.
What am I not understanding?
Thank you.
Best,
JJ

[JJ Zolper]

Has anyone experienced this same thing? Anyone have a lot of experience working with multiple databases using a router? It's just a little unclear how I'm supposed to better control it.

[Roger Gammans]

In allow_migrate () where you have 'return False', I've ended up (in my otherwise very similar router) with:

return db != 'mydb'

You certainly don't want return False as that will disable all migrations outside of your app_label, you want to return True,

only in the cases when the db is not your one; so everything else flows normally.  But globally returnning False disables the migrations in the normal case as you have found.

There are some awkward corner cases ; around mutli databases; some of which are probably a bug - (for instance - all migrations whether relevant or not are recorded in both databases) But I don't think that's your problem here.

allow_migrate(

self

, db, app_label, 

model_name=

None

, 

**hints

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