Re: Running pending migrations in Middleware

Yes, I do see several problems. Some of them:

- All middleware are run for every request
- What you're doing can slow down your request response time to minutes, depending on home many migrations you have
- Depending on your database, migrations might not be atomic thus causing conflicts
- You have no way to intervene when something goes south
- ...

I can elaborate in more detail when you want. But please, don't run migrations as part of the request-response cycle.

/Markus

On Sun, Jul 28, 2019, at 3:48 PM, David Grant wrote:
> Anyone see any problems with running migrations in Middleware?
>
> import logging
> import os
> import time
>
> from django.core.management import call_command
> from django.http import HttpResponse
>
> from products.models.models import AppVersion
>
> LOG = logging.getLogger(__name__)
>
>
> # Used for testing locally when the GAE_VERSION environment is not set
> FAKE_VERSION_TESTING = 8
>
>
> class MigrateMiddleware:
>
> def __init__(self, get_response):
> self.get_response = get_response
>
> def __call__(self, request):
> start_time = time.time()
> try:
> LOG.info("Running migrate middleware")
> # Figure out what version of our app is now deployed
> app_version, created =
> AppVersion.objects.get_or_create(version=os.getenv('GAE_VERSION',
> FAKE_VERSION_TESTING))
> if not app_version.migrations_succeeded or created:
> # Previous attempt at this deployed version failed, or this was
> a new deployment.
> try:
> call_command('migrate')
> except:
> return HttpResponse("Running a Django migration
> failed! Investigate.", status=500)
> app_version.migrations_succeeded = True
> app_version.save()
> finally:
> LOG.info("Took: %ss", time.time() - start_time)
> return self.get_response(request)
>
>
> It seems to work just fine in a quick test.
>
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