id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34165	migrate management command does not respect database parameter when adding Permissions.	Vasanth	David Wobrock	"When invoking migrate with a database parameter, the migration runs successfully. However, there seems to be a DB read request that runs after the migration. This call does not respect the db param and invokes the db router .

When naming the db as a parameter, all DB calls in the context of the migrate command are expected to use the database specified.

I came across this as I am currently using a thread-local variable to get the active DB with a custom DB router for a multi-tenant service .

**''Minimal example''** 

Setup the custom middleware and custom DB Router as show below. Then run any DB migration. We see that ""read {}"" is being printed before the exception message.

Ideally none of this code must be called as the DB was specified during management command.


{{{

from threading import local
from django.conf import settings

local_state = local()


class InvalidTenantException(Exception):
    pass


class TenantSubdomainMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        ## Get Subdomain
        host = request.get_host().split("":"")[0]
        local_state.subdomain = (
            # We assume single level of subdomain : app.service.com 
            # HOST_IP : used to for local dev. 
            host if host in settings.HOST_IP else host.split(""."")[0]
        )
        response = self.get_response(request)
        return response


class TenantDatabaseRouter:
    def _default_db(self):
        subdomain = getattr(local_state, ""subdomain"", None)
        if subdomain is not None and subdomain in settings.TENANT_MAP:
            db_name = settings.TENANT_MAP[local_state.subdomain]
            return db_name
        else:
            raise InvalidTenantException()

    def db_for_read(self, model, **hints):
        print(""read"", hints)
        return self._default_db()

    def db_for_write(self, model, **hints):
        print(""write"", hints)
        return self._default_db()

    def allow_relation(self, obj1, obj2, **hints):
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return None

## settings.py



MIDDLEWARE = [
    ""utils.tenant_db_router.TenantSubdomainMiddleware"",
    ""django.middleware.security.SecurityMiddleware"",
    ...
]

TENANT_MAP = {""localhost"":""default"", ""tenant_1"":""default""}
DATABASE_ROUTERS = [""utils.tenant_db_router.TenantDatabaseRouter""]
}}}
"	Bug	closed	contrib.auth	4.1	Normal	fixed		David Wobrock	Ready for checkin	1	0	0	0	0	0