Django message store

contrib · v0.1.0

Durable chat history in your Django database, with an admin and a read-only REST endpoint. Drop-in replacement for the room-chat kit's in-memory default.

Install	copit add @chanx-kit/django-message-store --variant django
Only on	django
Import from	django_message_store
Requires kits	room-chat
Python packages	chanx>=2.10.0,<3, django>=4.2, djangorestframework>=3.15
Tags	chat, django, orm, persistence, rest
Source	kits/django_message_store

Durable chat history in your Django database, with an admin and a read-only REST endpoint.

copit add @chanx-kit/django-message-store --variant django   # also installs: room-chat

Django only. This kit ships models, migrations, admin and a DRF viewset, none of which have a fast-channels equivalent, so it declares only_variants: [django] and copit refuses to install it into a project that has not selected that variant.

Why

The room-chat kit defaults to InMemoryMessageStore, a bounded deque per room. It loses everything on restart and each worker holds its own copy, so which history a client gets depends on which worker answered. This keeps it in your database instead.

Use it

Add the app and run its migration:

INSTALLED_APPS = [..., "rest_framework", "app.ws_kits.django_message_store"]

python manage.py migrate

from app.ws_kits.django_message_store.store import DjangoMessageStore
from app.ws_kits.room_chat import RoomChatTopic


class DurableChatTopic(RoomChatTopic):
    message_store = DjangoMessageStore()

Nothing else changes: it satisfies the same MessageStore protocol.

The store is imported from .store, not from the package. A Django app's __init__ is imported before the app registry is ready, so re-exporting a model from there raises AppRegistryNotReady at startup.

The history API

path("api/chat/", include("app.ws_kits.django_message_store.urls")),

GET /api/chat/history/?room=general&page_size=50

Paginated, newest first. id is the kit's own entry id, the same one the message carried over the websocket, so a client can match the two. It is read-only: a message created here would be persisted without any connected client being told, so posting is 405. Add permission classes to the viewset if history is not public.

What is stored

ChatEntryRecord flattens ChatEntry: entry_id, room, author_id, author_name, body, sent_at, indexed on (room, -sent_at). The model is deliberately not the wire contract. That belongs to room-chat, so a schema change here cannot alter what clients receive.

Trade-offs

• Every message costs a write. For very busy rooms, batch or queue the append.
• backlog() reads the latest limit rows and reverses them in Python, which is fine for the tens of messages a client replays. Paginate through the REST endpoint for anything larger.
• History grows without bound. Add a retention job if that matters.