r4fek/django-cassandra-engine

from django.apps import apps
from django.core.management.base import BaseCommand, CommandError
from django.db import connections

from django_cassandra_engine.models import DjangoCassandraModel
from django_cassandra_engine.utils import get_engine_from_db_alias

from ...compat import Model, management


class Command(BaseCommand):
    help = "Sync Cassandra database(s)"

    def add_arguments(self, parser):
        parser.add_argument(
            "--database",
            action="store",
            dest="database",
            default=None,
            help="Nominates a database to synchronize.",
        )

    @staticmethod
    def _import_management():
        """
        Import the 'management' module within each installed app, to register
        dispatcher events.
        """
        from importlib import import_module

        for app_config in apps.get_app_configs():
            try:
                import_module(".management", app_config.name)
            except SystemError:
                # We get SystemError if INSTALLED_APPS contains the
                # name of a class rather than a module
                pass
            except ImportError as exc:
                # This is slightly hackish. We want to ignore ImportErrors
                # if the "management" module itself is missing -- but we don't
                # want to ignore the exception if the management module exists
                # but raises an ImportError for some reason. The only way we
                # can do this is to check the text of the exception. Note that
                # we're a bit broad in how we check the text, because different
                # Python implementations may not use the same text.
                # CPython uses the text "No module named management"
                # PyPy uses "No module named myproject.myapp.management"
                msg = exc.args[0]
                if not msg.startswith("No module named") or "management" not in msg:
                    raise

    def sync(self, alias):
        engine = get_engine_from_db_alias(alias)

        if engine != "django_cassandra_engine":
            raise CommandError("Database {} is not cassandra!".format(alias))

        connection = connections[alias]
        connection.connect()
        options = connection.settings_dict.get("OPTIONS", {})
        keyspace = connection.settings_dict["NAME"]
        replication_opts = options.get("replication", {})
        strategy_class = replication_opts.pop("strategy_class", "SimpleStrategy")
        replication_factor = replication_opts.pop("replication_factor", 1)

        self.stdout.write(
            "Creating keyspace {} [CONNECTION {}] ..".format(keyspace, alias)
        )

        if strategy_class == "SimpleStrategy":
            management.create_keyspace_simple(
                keyspace, replication_factor, connections=[alias]
            )
        else:
            management.create_keyspace_network_topology(
                keyspace, replication_opts, connections=[alias]
            )

        connection.connection.cluster.refresh_schema_metadata()
        connection.connection.cluster.schema_metadata_enabled = True

        for app_name, app_models in connection.introspection.cql_models.items():
            for model in app_models:
                self.stdout.write("Syncing %s.%s" % (app_name, model.__name__))
                # patch this object used for type check in management.sync_table()
                management.Model = (Model, DjangoCassandraModel)
                management.sync_table(model, keyspaces=[keyspace], connections=[alias])

    def handle(self, **options):
        self._import_management()

        database = options.get("database")
        if database is not None:
            return self.sync(database)

        cassandra_alias = None
        for alias in connections:
            engine = get_engine_from_db_alias(alias)
            if engine == "django_cassandra_engine":
                self.sync(alias)
                cassandra_alias = alias

        if cassandra_alias is None:
            raise CommandError(
                "Please add django_cassandra_engine backend to DATABASES!"
            )