# 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.