pondsocket 0.0.4

PondSocket - channel-based real-time framework with bring-your-own-server design.

pondsocket

PondSocket - channel-based real-time framework for Python. Bring-your-own-server design: the core knows nothing about HTTP frameworks or WebSocket libraries. You build the layered API (Server -> Endpoint -> Channel -> User), and an adapter (e.g. pondsocket-asgi) bridges it to your HTTP stack.

Install

pip install pondsocket
pip install "pondsocket[redis]"   # multi-node deployments

Concepts

PondSocket     top-level facade, holds endpoints
  └── Endpoint   one URL path, runs the connection auth handler, owns transports
        └── Lobby     one channel pattern (e.g. "/chat/:room_id"), holds shared middleware
              └── Channel    one live channel instance, holds users + presence

Five contexts, scoped to lifecycle moments

Context	When	What it decides / does
ConnectionContext	HTTP upgrade	accept / decline socket, set initial assigns
JoinContext	per channel join	accept / decline membership, track presence
EventContext	per incoming event	broadcast, reply, update presence/assigns, evict
OutgoingContext	per recipient, per send	transform payload or block delivery
LeaveContext	user gone	final cleanup (user already removed)

Minimal example

from pondsocket import ConnectionContext, EventContext, JoinContext, PondSocket


async def auth(ctx: ConnectionContext) -> None:
    if ctx.query.get("token") != "secret":
        ctx.decline(401, "Invalid token")
        return
    ctx.accept(user_id=ctx.query.get("uid", "anon"))


async def on_join(ctx: JoinContext) -> None:
    await ctx.accept()
    await ctx.track({"status": "online"})


async def on_message(ctx: EventContext) -> None:
    await ctx.broadcast(ctx.event_name, ctx.get_payload())


pond = PondSocket()
endpoint = pond.create_endpoint("/api/socket", auth)
lobby = endpoint.create_channel("/chat/:room_id", on_join)
lobby.on_message("message", on_message)

To actually serve traffic, wrap pond in an adapter — see pondsocket-asgi for the canonical one.

Distributed (multi-node)

from redis.asyncio import Redis
from pondsocket import PondSocket
from pondsocket.distributed import RedisPubSub

redis = Redis(host="localhost", port=6379)
pubsub = RedisPubSub(redis, owns_client=True)
pond = PondSocket(pubsub=pubsub)

Cross-node broadcasts and presence events propagate via Redis PSUBSCRIBE. node_id is auto-generated when a pubsub is configured. Each broadcast carries the nodeId so emitters filter their own echo.

See pondsocket.distributed.RedisPubSub for the implementation. The PubSub protocol is implementable for other backends.

Hooks & metrics

from pondsocket import Hooks, NoopMetrics, Options, PondSocket, TokenBucketRateLimiter

hooks = Hooks(
    rate_limiter=TokenBucketRateLimiter(rate=10, capacity=20),
    metrics=NoopMetrics(),
)
pond = PondSocket(options=Options(hooks=hooks))

Auto-fired by the framework: connection_opened/connection_closed, channel_created/channel_destroyed/channel_joined/channel_left, plus on_connect/on_disconnect/before_join/after_join/before_message/after_message.

Opt-in middleware factories for per-handler instrumentation:

from pondsocket import with_metrics, with_rate_limiter

lobby.on_message(
    "message",
    on_message,
    with_rate_limiter(hooks, key_fn=lambda msg: msg.user.id),
    with_metrics(hooks),
)

Testing

InMemoryTransport is a public test utility that satisfies the Transport protocol without any network I/O:

from pondsocket import InMemoryTransport

t = InMemoryTransport("alice")
await endpoint.register_transport(t)

await t.push_inbound(some_event)
sent = await t.receive_sent()

Public API

from pondsocket import ...

• Core: PondSocket, Endpoint, Lobby, Channel, Options, Event, User, MessageEvent, RecipientSpec
• Contexts: ConnectionContext, JoinContext, EventContext, LeaveContext, OutgoingContext
• Transport: Transport (Protocol), InMemoryTransport, SSEServerTransport, TransportType, OnCloseCallback, OnMessageHandler
• PubSub: PubSub (Protocol), LocalPubSub, format_topic, match_topic, PubSubClosedError
• Hooks: Hooks, RateLimiter, MetricsCollector, NoopMetrics, TokenBucketRateLimiter, with_rate_limiter, with_metrics
• Wire: event_to_json, event_to_wire, parse_inbound_text, wire_to_event, event_to_pubsub_bytes, pubsub_bytes_to_event
• Errors: PondError, status constructors, error_event

License

GPL-3.0-or-later.