#34165: migrate management command does not respect database parameter for all
DB
calls
----------------------------+--------------------------------------
Reporter: Vasanth | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 4.1
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------------------------
Description changed by Vasanth:
Old description:
> 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''**
>
> {{{
>
> 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):
> return self._default_db()
>
> def db_for_write(self, model, **hints):
> return self._default_db()
>
> def allow_relation(self, obj1, obj2, **hints):
> return True
>
> def allow_migrate(self, db, app_label, model_name=None, **hints):
> return True
>
> ## 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"]
> }}}
New description:
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. 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):
return self._default_db()
def db_for_write(self, model, **hints):
return self._default_db()
def allow_relation(self, obj1, obj2, **hints):
return True
def allow_migrate(self, db, app_label, model_name=None, **hints):
return True
## 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"]
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/34165#comment:1>
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