#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''**
>
> 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"]
> }}}
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. 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"]
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/34165#comment:2>
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