use customized constance (#4191)

thirdpart/constance/backends/database/__init__.py

@@ -0,0 +1,111 @@
+from django.core.cache import caches
+from django.core.cache.backends.locmem import LocMemCache
+from django.core.exceptions import ImproperlyConfigured
+from django.db import OperationalError, ProgrammingError
+from django.db.models.signals import post_save
+
+from .. import Backend
+from ... import settings, signals, config
+
+
+class DatabaseBackend(Backend):
+    def __init__(self):
+        from .models import Constance
+        self._model = Constance
+        self._prefix = settings.DATABASE_PREFIX
+        self._autofill_timeout = settings.DATABASE_CACHE_AUTOFILL_TIMEOUT
+        self._autofill_cachekey = 'autofilled'
+
+        if not self._model._meta.installed:
+            raise ImproperlyConfigured(
+                "The constance.backends.database app isn't installed "
+                "correctly. Make sure it's in your INSTALLED_APPS setting.")
+
+        if settings.DATABASE_CACHE_BACKEND:
+            self._cache = caches[settings.DATABASE_CACHE_BACKEND]
+            if isinstance(self._cache, LocMemCache):
+                raise ImproperlyConfigured(
+                    "The CONSTANCE_DATABASE_CACHE_BACKEND setting refers to a "
+                    "subclass of Django's local-memory backend (%r). Please "
+                    "set it to a backend that supports cross-process caching."
+                    % settings.DATABASE_CACHE_BACKEND)
+        else:
+            self._cache = None
+        self.autofill()
+        # Clear simple cache.
+        post_save.connect(self.clear, sender=self._model)
+
+    def add_prefix(self, key):
+        return "%s%s" % (self._prefix, key)
+
+    def autofill(self):
+        if not self._autofill_timeout or not self._cache:
+            return
+        full_cachekey = self.add_prefix(self._autofill_cachekey)
+        if self._cache.get(full_cachekey):
+            return
+        autofill_values = {}
+        autofill_values[full_cachekey] = 1
+        for key, value in self.mget(settings.CONFIG):
+            autofill_values[self.add_prefix(key)] = value
+        self._cache.set_many(autofill_values, timeout=self._autofill_timeout)
+
+    def mget(self, keys):
+        if not keys:
+            return
+        keys = {self.add_prefix(key): key for key in keys}
+        try:
+            stored = self._model._default_manager.filter(key__in=keys)
+            for const in stored:
+                yield keys[const.key], const.value
+        except (OperationalError, ProgrammingError):
+            pass
+
+    def get(self, key):
+        key = self.add_prefix(key)
+        if self._cache:
+            value = self._cache.get(key)
+            if value is None:
+                self.autofill()
+                value = self._cache.get(key)
+        else:
+            value = None
+        if value is None:
+            try:
+                value = self._model._default_manager.get(key=key).value
+            except (OperationalError, ProgrammingError, self._model.DoesNotExist):
+                pass
+            else:
+                if self._cache:
+                    self._cache.add(key, value)
+        return value
+
+    def set(self, key, value):
+        key = self.add_prefix(key)
+
+        try:
+            constance = self._model._default_manager.get(key=key)
+        except (OperationalError, ProgrammingError):
+            # database is not created, noop
+            return
+        except self._model.DoesNotExist:
+            old_value = None
+            constance = self._model._default_manager.create(key=key, value=value)
+        else:
+            old_value = constance.value
+            constance.value = value
+            constance.save()
+
+        if self._cache:
+            self._cache.set(key, value)
+
+        signals.config_updated.send(
+            sender=config, key=key, old_value=old_value, new_value=value
+        )
+
+    def clear(self, sender, instance, created, **kwargs):
+        if self._cache and not created:
+            keys = [self.add_prefix(k) for k in settings.CONFIG]
+            keys.append(self.add_prefix(self._autofill_cachekey))
+            self._cache.delete_many(keys)
+            self.autofill()