Add kaya-session-memcache package for memcached-backed session storage

packages/kaya-session-memcache/README.md

@@ -0,0 +1,52 @@
+# kaya-session-memcache
+
+Memcached-backed session storage for the Kaya web framework.
+
+Provides `MemcacheSessionStore`, a `SessionStore` implementation (from
+`kaya-session`) that persists session data in memcached via `aiomcache`, so
+sessions are shared across processes and hosts.
+
+## Usage
+
+```python
+import aiomcache
+
+from kaya.core import KayaApp, HttpContext
+from kaya.session import SessionMixin
+from kaya.session_memcache import MemcacheSessionStore
+
+client = aiomcache.Client('127.0.0.1', 11211)
+session = SessionMixin(MemcacheSessionStore(client))
+app = KayaApp(mixins=[session])
+
+@app.GET('/')
+async def home(ctx: HttpContext):
+    n = ctx.session.get('visits', 0) + 1
+    ctx.session['visits'] = n
+    await ctx.send_str(200, f'visits: {n}')
+```
+
+Sessions are stored under keys with the prefix `kaya:session:` (configurable
+via the `prefix` argument). Server-side expiry uses memcached item expiration
+and slides on each access when the session mixin passes a `max_age`. TTLs
+larger than 30 days are automatically converted to absolute Unix timestamps,
+as required by the memcached protocol.
+
+## Serialization
+
+Session data is serialized with `pickle` by default, so arbitrary Python
+objects can be stored. A different serializer can be plugged in via the
+`dumps`/`loads` arguments:
+
+```python
+import json
+
+store = MemcacheSessionStore(
+    client,
+    dumps=lambda d: json.dumps(d).encode('utf-8'),
+    loads=lambda b: json.loads(b.decode('utf-8')),
+)
+```
+
+**Warning:** pickle deserialization of untrusted data is unsafe. Only use the
+default serializer with a trusted memcached server.

packages/kaya-session-memcache/pyproject.toml

@@ -0,0 +1,57 @@
+[build-system]
+requires = ["setuptools>=61.0", "setuptools-scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "kaya-session-memcache"
+dynamic = ["version"]
+authors = [
+  { name="Walter Oggioni", email="oggioni.walter@gmail.com" },
+]
+description = "Memcached-backed session storage for the Kaya lightweight ASGI web framework"
+readme = "README.md"
+requires-python = ">=3.10"
+license = "MIT"
+classifiers = [
+        'Development Status :: 3 - Alpha',
+        'Topic :: Utilities',
+        'Intended Audience :: System Administrators',
+        'Intended Audience :: Developers',
+        'Environment :: Console',
+        'Programming Language :: Python :: 3',
+]
+
+dependencies = [
+    "kaya-session",
+    "aiomcache>=0.8",
+]
+
+[project.optional-dependencies]
+dev = [
+    "build", "mypy", "ipdb", "twine"
+]
+
+[project.urls]
+"Homepage" = "https://github.com/woggioni/kaya"
+"Bug Tracker" = "https://github.com/woggioni/kaya/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+namespaces = true
+
+[tool.mypy]
+python_version = "3.12"
+disallow_untyped_defs = true
+show_error_codes = true
+no_implicit_optional = true
+warn_return_any = true
+warn_unused_ignores = true
+exclude = ["scripts", "docs", "test"]
+strict = true
+
+[tool.setuptools_scm]
+root = "../.."
+version_file = "src/kaya/session_memcache/_version.py"
+
+[tool.setuptools_scm.tag]
+prefix = "release/"

packages/kaya-session-memcache/src/kaya/session_memcache/__init__.py

@@ -0,0 +1,6 @@
+from ._store import MemcacheSessionStore
+
+
+__all__ = [
+    'MemcacheSessionStore',
+]

packages/kaya-session-memcache/src/kaya/session_memcache/_store.py

@@ -0,0 +1,76 @@
+import pickle
+from time import time
+from typing import Any, Callable, Optional
+
+import aiomcache
+
+from kaya.session import Session, SessionStore
+
+_THIRTY_DAYS = 30 * 24 * 60 * 60
+
+
+def _exptime(max_age: int, clock: Callable[[], float]) -> int:
+    """Convert a relative TTL to a memcached ``exptime`` value.
+
+    Memcached interprets ``exptime`` values larger than 30 days as absolute
+    Unix timestamps, so large TTLs must be converted explicitly.
+    """
+    if max_age > _THIRTY_DAYS:
+        return int(clock()) + max_age
+    return max_age
+
+
+class MemcacheSessionStore(SessionStore):
+    """Memcached-backed session store.
+
+    Suitable for multi-process and multi-host deployments: session data is
+    shared between all application instances connected to the same memcached
+    server.
+
+    Server-side expiry is delegated to memcached item expiration. When
+    ``max_age`` is provided, active sessions slide the expiry window on each
+    access. TTLs larger than 30 days are converted to absolute Unix
+    timestamps, as required by the memcached protocol.
+
+    Session data is serialized with ``pickle`` by default, so arbitrary
+    Python objects can be stored. Custom serializers can be plugged in via
+    the ``dumps``/``loads`` arguments. Only connect this store to a trusted
+    memcached server, as pickle deserialization of untrusted data is unsafe.
+    """
+
+    def __init__(
+        self,
+        client: aiomcache.Client,
+        prefix: str = "kaya:session:",
+        dumps: Callable[[dict[str, Any]], bytes] = pickle.dumps,
+        loads: Callable[[bytes], dict[str, Any]] = pickle.loads,
+        clock: Callable[[], float] = time,
+    ) -> None:
+        self._client = client
+        self._prefix = prefix
+        self._dumps = dumps
+        self._loads = loads
+        self._clock = clock
+
+    def _key(self, session_id: str) -> bytes:
+        return f"{self._prefix}{session_id}".encode()
+
+    async def load(self, session_id: str, max_age: Optional[int] = None) -> Optional[Session]:
+        key = self._key(session_id)
+        payload = await self._client.get(key)
+        if payload is None:
+            return None
+
+        if max_age is not None:
+            await self._client.touch(key, _exptime(max_age, self._clock))
+
+        data = self._loads(payload)
+        return Session(session_id, data)
+
+    async def save(self, session_id: str, session: Session, max_age: Optional[int] = None) -> None:
+        payload = self._dumps(dict(session))
+        exptime = _exptime(max_age, self._clock) if max_age is not None else 0
+        await self._client.set(self._key(session_id), payload, exptime=exptime)
+
+    async def delete(self, session_id: str) -> None:
+        await self._client.delete(self._key(session_id))

packages/kaya-session-memcache/tests/test_store.py

@@ -0,0 +1,203 @@
+import unittest
+from datetime import datetime, timezone
+from typing import Optional
+
+import httpx
+from pwo import async_test
+
+from kaya.core import KayaApp, HttpContext
+from kaya.session import Session, SessionMixin
+from kaya.session_memcache import MemcacheSessionStore
+
+
+class FakeClock:
+    def __init__(self, start: float = 1_000_000.0) -> None:
+        self._now = start
+
+    def __call__(self) -> float:
+        return self._now
+
+    def advance(self, seconds: float) -> None:
+        self._now += seconds
+
+
+class StubMemcacheClient:
+    """In-memory stub implementing the aiomcache.Client subset used by the store."""
+
+    def __init__(self, clock: FakeClock) -> None:
+        self._clock = clock
+        self._data: dict[bytes, bytes] = {}
+        self._expires: dict[bytes, float] = {}
+        self.set_exptimes: list[int] = []
+        self.touch_exptimes: list[int] = []
+
+    def _expired(self, key: bytes) -> bool:
+        expires = self._expires.get(key)
+        return expires is not None and self._clock() > expires
+
+    async def get(self, key: bytes) -> Optional[bytes]:
+        if self._expired(key):
+            self._data.pop(key, None)
+            self._expires.pop(key, None)
+            return None
+        return self._data.get(key)
+
+    async def set(self, key: bytes, value: bytes, exptime: int = 0) -> bool:
+        self.set_exptimes.append(exptime)
+        self._data[key] = value
+        if exptime > 0:
+            self._expires[key] = self._clock() + exptime
+        else:
+            self._expires.pop(key, None)
+        return True
+
+    async def delete(self, key: bytes) -> bool:
+        existed = key in self._data
+        self._data.pop(key, None)
+        self._expires.pop(key, None)
+        return existed
+
+    async def touch(self, key: bytes, exptime: int) -> bool:
+        self.touch_exptimes.append(exptime)
+        if self._expired(key) or key not in self._data:
+            return False
+        self._expires[key] = self._clock() + exptime
+        return True
+
+
+class MemcacheSessionStoreTest(unittest.TestCase):
+    clock: FakeClock
+    client: StubMemcacheClient
+    store: MemcacheSessionStore
+
+    def setUp(self) -> None:
+        self.clock = FakeClock()
+        self.client = StubMemcacheClient(self.clock)
+        self.store = MemcacheSessionStore(self.client, clock=self.clock)  # type: ignore[arg-type]
+
+    @async_test
+    async def test_save_and_load_round_trip(self) -> None:
+        session = Session('abc', {'foo': 'bar', 'n': 42})
+        await self.store.save('abc', session)
+        loaded = await self.store.load('abc')
+        self.assertIsNotNone(loaded)
+        assert loaded is not None
+        self.assertEqual('abc', loaded.id)
+        self.assertEqual({'foo': 'bar', 'n': 42}, dict(loaded))
+
+    @async_test
+    async def test_load_unknown_session_returns_none(self) -> None:
+        self.assertIsNone(await self.store.load('missing'))
+
+    @async_test
+    async def test_delete_removes_session(self) -> None:
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}))
+        await self.store.delete('abc')
+        self.assertIsNone(await self.store.load('abc'))
+
+    @async_test
+    async def test_save_with_max_age_expires(self) -> None:
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=60)
+        self.assertIsNotNone(await self.store.load('abc'))
+        self.clock.advance(61)
+        self.assertIsNone(await self.store.load('abc'))
+
+    @async_test
+    async def test_save_without_max_age_never_expires(self) -> None:
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}))
+        self.assertEqual([0], self.client.set_exptimes)
+        self.clock.advance(10_000_000)
+        self.assertIsNotNone(await self.store.load('abc'))
+
+    @async_test
+    async def test_load_slides_expiry_when_max_age_given(self) -> None:
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=60)
+        self.clock.advance(50)
+        loaded = await self.store.load('abc', max_age=60)
+        self.assertIsNotNone(loaded)
+        self.assertEqual([60], self.client.touch_exptimes)
+        self.clock.advance(50)
+        self.assertIsNotNone(await self.store.load('abc'))
+
+    @async_test
+    async def test_exptime_over_30_days_converted_to_absolute_timestamp(self) -> None:
+        max_age = 40 * 24 * 60 * 60
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
+        self.assertEqual([int(self.clock()) + max_age], self.client.set_exptimes)
+
+    @async_test
+    async def test_exptime_exactly_30_days_stays_relative(self) -> None:
+        max_age = 30 * 24 * 60 * 60
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
+        self.assertEqual([max_age], self.client.set_exptimes)
+
+    @async_test
+    async def test_touch_over_30_days_converted_to_absolute_timestamp(self) -> None:
+        max_age = 40 * 24 * 60 * 60
+        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
+        self.clock.advance(100)
+        await self.store.load('abc', max_age=max_age)
+        self.assertEqual([int(self.clock()) + max_age], self.client.touch_exptimes)
+
+    @async_test
+    async def test_pickle_round_trip_of_non_json_values(self) -> None:
+        now = datetime(2026, 7, 20, 12, 0, 0, tzinfo=timezone.utc)
+        session = Session('abc', {'when': now, 'blob': b'\x00\x01', 'items': {1, 2, 3}})
+        await self.store.save('abc', session)
+        loaded = await self.store.load('abc')
+        self.assertIsNotNone(loaded)
+        assert loaded is not None
+        self.assertEqual(now, loaded['when'])
+        self.assertEqual(b'\x00\x01', loaded['blob'])
+        self.assertEqual({1, 2, 3}, loaded['items'])
+
+    @async_test
+    async def test_custom_prefix(self) -> None:
+        store = MemcacheSessionStore(self.client, prefix='myapp:sess:', clock=self.clock)  # type: ignore[arg-type]
+        await store.save('abc', Session('abc', {'foo': 'bar'}))
+        self.assertIn(b'myapp:sess:abc', self.client._data)
+        self.assertNotIn(b'kaya:session:abc', self.client._data)
+
+    @async_test
+    async def test_custom_serializer(self) -> None:
+        import json
+
+        store = MemcacheSessionStore(
+            self.client,  # type: ignore[arg-type]
+            dumps=lambda d: json.dumps(d).encode('utf-8'),
+            loads=lambda b: json.loads(b.decode('utf-8')),
+            clock=self.clock,
+        )
+        await store.save('abc', Session('abc', {'foo': 'bar'}))
+        self.assertEqual(b'{"foo": "bar"}', self.client._data[b'kaya:session:abc'])
+        loaded = await store.load('abc')
+        self.assertIsNotNone(loaded)
+        assert loaded is not None
+        self.assertEqual({'foo': 'bar'}, dict(loaded))
+
+
+class MemcacheSessionIntegrationTest(unittest.TestCase):
+    app: KayaApp
+
+    def setUp(self) -> None:
+        store = MemcacheSessionStore(StubMemcacheClient(FakeClock()))  # type: ignore[arg-type]
+        self.app = KayaApp(mixins=[SessionMixin(store)])
+
+        @self.app.GET('/')
+        async def home(ctx: HttpContext) -> None:
+            n = ctx.session.get('visits', 0) + 1
+            ctx.session['visits'] = n
+            await ctx.send_str(200, f'visits: {n}')
+
+    @async_test
+    async def test_session_persists_across_requests(self) -> None:
+        transport = httpx.ASGITransport(app=self.app)
+        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
+            r = await client.get('/')
+            self.assertEqual(200, r.status_code)
+            self.assertEqual('visits: 1', r.text)
+            self.assertIn('Set-Cookie', r.headers)
+
+            r = await client.get('/')
+            self.assertEqual(200, r.status_code)
+            self.assertEqual('visits: 2', r.text)