post_migrate_handler

[zN3utr4l]

Python version
3.8

Django version
3.2.16

Package version
0.22.2

Current behavior (bug description)
The current behavior of the post-migration signal (post_migrate_handler) does not take into account any routing of the databases

from django.conf import settings


class DatabaseAppsRouter(object):
    """

        arouter to control all database operations on models for different
        databases.

        in case an app is not set in settings.DATABASE_APPS_MAPPING, the router
        will fallback to the `default` database.

        Settings example:

        DATABASE_APPS_MAPPING = {'app1': 'db1', 'app2': 'db2'}
    """

    def db_for_read(self, model, **hints):
        """Point all read operations to the specific database"""
        if model._meta.app_label in settings.DATABASE_APPS_MAPPING:
            return settings.DATABASE_APPS_MAPPING[model._meta.app_label]

        return None

    def db_for_write(self, model, **hints):
        """Point all write operations to the specific database"""
        if model._meta.app_label in settings.DATABASE_APPS_MAPPING:
            return settings.DATABASE_APPS_MAPPING[model._meta.app_label]

        return None

    def allow_relation(self, obj1, obj2, **hints):
        """Allow any relation between apps that use the same database"""
        db1 = settings.DATABASE_APPS_MAPPING[obj1._meta.app_label]
        db2 = settings.DATABASE_APPS_MAPPING[obj2._meta.app_label]

        if db1 and db2:
            return db1 == db2

        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """Make sure that apps only appear in the related database"""

        if db in settings.DATABASE_APPS_MAPPING.values():
            return settings.DATABASE_APPS_MAPPING[app_label] == db

        elif app_label in settings.DATABASE_APPS_MAPPING:
            return False

        return None

DATABASES = {
    'default': {
        'ENGINE': 'timescale.db.backends.postgresql',
        'NAME': TIMESCALE_DB_HOST_FORMATTED['Database'],
        'USER': TIMESCALE_DB_HOST_FORMATTED['Username'],
        'PASSWORD': TIMESCALE_DB_HOST_FORMATTED['Password'],
        'HOST': TIMESCALE_DB_HOST_FORMATTED['Host'],
        'PORT': TIMESCALE_DB_PORT,
        'OPTIONS': {
            'client_encoding': 'UTF8',
            # 'isolation_level': psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE,
        }
    },
    'collector': {
        'ENGINE': 'djongo',
        'NAME': 'Database',
        'ENFORCE_SCHEMA': True,
        'CLIENT': {
            'host': MONGO_DB_HOST
        }
    }
}


DATABASE_APPS_MAPPING = {
    'contenttypes': 'default',
    'auth': 'default',
    'admin': 'default',
    'django_cache': 'default',
    'sessions': 'default',
    'staticfiles': 'default',
    'admin_interface': 'default',
    'collector': 'djongo(mongodb)',
    'main': 'default',
}

DATABASE_ROUTERS = ['routers.DatabaseAppsRouter']

Workaround

def apply_theme(sender, **kwargs):
    from django.conf import settings
    from admin_interface.models import Theme
    from admin_interface.cache import del_cached_active_theme

    del_cached_active_theme()
    theme = Theme.get_active_theme('default')
    theme.logo = ....
    theme.favicon = ....
    theme.save()


class MainConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'main'
    verbose_name = 'analyser configuration'

    def ready(self) -> None:
        from admin_interface.models import Theme

        Theme.post_migrate_handler = apply_theme
        if 'admin_interface_theme' in connection.introspection.table_names():
            apply_theme(None)

[fabiocaccamo]

@zN3utr4l you are not passing **kwargs to apply_theme function, the function does nothing because it doesn't enter the condition.

Could you provide a failing test please?

[zN3utr4l]

if I don't override your post migrate function it fails.

Try to copy my routing class and create 2 databases in django, I think it's ok they are on the same system too (postgresql) and in the routing dictionary you put two projects, yours with routing on default and another one with routing on default2, you run python manage.py migrate --database default and python manage.py migrate --database default2 and in the second call it should go wrong because you try to do in your function .using('database2') but the migrations of your project they are on default.

[fabiocaccamo]

@zN3utr4l does this worked correctly for you with the 0.22.1 version?

[zN3utr4l]

yes, because there was no .using(db) and the queries were addressed by themselves via my file routing

[fabiocaccamo]

@zN3utr4l I understand. If you can submit a PR with a failing test (that should succeed) I will fix it and publish a new release quickly.

[zN3utr4l]

At the moment I can't, overriding your function seems to work for now

[fabiocaccamo]

@VaZark have you the time to add a test for this issue?

[VaZark]

I think if we set the database=None, we can be backward-compatible . I'll add a test too

    def get_active_theme(database=None):
        objs_manager = Theme.objects if database is None else Theme.objects.using(database)

[VaZark]

@fabiocaccamo do you know any examples or resources with testing with a DB Router ?? I'm unable to find much about it.

[fabiocaccamo]

@VaZark there is a good example at the top of this issue.