first comit

venv/lib/python3.10/site-packages/django/contrib/sessions/backends/cache.py

@@ -0,0 +1,85 @@
+from django.conf import settings
+from django.contrib.sessions.backends.base import CreateError, SessionBase, UpdateError
+from django.core.cache import caches
+
+KEY_PREFIX = "django.contrib.sessions.cache"
+
+
+class SessionStore(SessionBase):
+    """
+    A cache-based session store.
+    """
+
+    cache_key_prefix = KEY_PREFIX
+
+    def __init__(self, session_key=None):
+        self._cache = caches[settings.SESSION_CACHE_ALIAS]
+        super().__init__(session_key)
+
+    @property
+    def cache_key(self):
+        return self.cache_key_prefix + self._get_or_create_session_key()
+
+    def load(self):
+        try:
+            session_data = self._cache.get(self.cache_key)
+        except Exception:
+            # Some backends (e.g. memcache) raise an exception on invalid
+            # cache keys. If this happens, reset the session. See #17810.
+            session_data = None
+        if session_data is not None:
+            return session_data
+        self._session_key = None
+        return {}
+
+    def create(self):
+        # Because a cache can fail silently (e.g. memcache), we don't know if
+        # we are failing to create a new session because of a key collision or
+        # because the cache is missing. So we try for a (large) number of times
+        # and then raise an exception. That's the risk you shoulder if using
+        # cache backing.
+        for i in range(10000):
+            self._session_key = self._get_new_session_key()
+            try:
+                self.save(must_create=True)
+            except CreateError:
+                continue
+            self.modified = True
+            return
+        raise RuntimeError(
+            "Unable to create a new session key. "
+            "It is likely that the cache is unavailable."
+        )
+
+    def save(self, must_create=False):
+        if self.session_key is None:
+            return self.create()
+        if must_create:
+            func = self._cache.add
+        elif self._cache.get(self.cache_key) is not None:
+            func = self._cache.set
+        else:
+            raise UpdateError
+        result = func(
+            self.cache_key,
+            self._get_session(no_load=must_create),
+            self.get_expiry_age(),
+        )
+        if must_create and not result:
+            raise CreateError
+
+    def exists(self, session_key):
+        return (
+            bool(session_key) and (self.cache_key_prefix + session_key) in self._cache
+        )
+
+    def delete(self, session_key=None):
+        if session_key is None:
+            if self.session_key is None:
+                return
+            session_key = self.session_key
+        self._cache.delete(self.cache_key_prefix + session_key)
+
+    @classmethod
+    def clear_expired(cls):
+        pass