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[Bug] WebSocket Streams: stream registry is global, two clients with the same stream name get each other's data

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
88/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
backend

Research direction

Start in common/src/binance_common/websocket.py with WebSocketStreamBase: find the module-level maps global_stream_connections and global_user_stream_connections, then every place they are read or written — the subscribe filter, on, unsubscribe, and reconnect cleanup — and move them to per-instance attributes initialized in __init__. Run the self-contained aiohttp reproduction script from the issue body first to confirm the wrong output, then re-run it to check that each server gets its own SUBSCRIBE and fut_cb receives {'venue': 'futures'}. Check the repo's existing websocket tests still pass, since pooling and dedup logic depend on this registry.

Written by the indexing model from the issue text.

Description

Summary

WebSocketStreamBase keeps its stream-to-connection registry in two module-level objects (global_stream_connections, global_user_stream_connections in common/src/binance_common/websocket.py). Every client in the process shares them, keyed only by stream name.

Spot and USDⓈ-M Futures use the same stream names (btcusdt@aggTrade, btcusdt@depth, ...), and so do mainnet and testnet. When two stream clients in one process subscribe to the same name:

  • the second client never sends SUBSCRIBE, because the name is already registered;
  • its callback is attached to the first client's connection, so it receives the other venue's data, with no error.

Reproduce

Self-contained: one local aiohttp server with two endpoints standing in for two venues; each tags its messages with its name. binance-common==4.5.1 (same as master at 43f19a9), Python 3.13.

import asyncio, json, logging
from aiohttp import web
from binance_common.configuration import ConfigurationWebSocketStreams
from binance_common.websocket import WebSocketStreamBase, RequestStream
logging.disable(logging.CRITICAL)
subs = {"spot": [], "futures": []}
def mk(name):
    async def handler(request):
        ws = web.WebSocketResponse(); await ws.prepare(request)
        async for msg in ws:
            d = json.loads(msg.data)
            if d["method"] == "SUBSCRIBE":
                subs[name] += d["params"]
                await ws.send_json({"id": d["id"], "result": None})
                for s in d["params"]:
                    await ws.send_json({"stream": s, "data": {"venue": name}})
        return ws
    return handler
async def main():
    app = web.Application()
    app.router.add_get("/spot/stream", mk("spot")); app.router.add_get("/fut/stream", mk("futures"))
    r = web.AppRunner(app); await r.setup(); await web.TCPSite(r, "127.0.0.1", 18766).start()
    spot = WebSocketStreamBase(ConfigurationWebSocketStreams(stream_url="ws://127.0.0.1:18766/spot/stream"))
    fut = WebSocketStreamBase(ConfigurationWebSocketStreams(stream_url="ws://127.0.0.1:18766/fut/stream"))
    await spot.create_connection(); await fut.create_connection()
    got = {"spot_cb": [], "fut_cb": []}
    h1 = await RequestStream(spot, "btcusdt@aggTrade"); h1.on("message", lambda d: got["spot_cb"].append(d))
    h2 = await RequestStream(fut, "btcusdt@aggTrade");  h2.on("message", lambda d: got["fut_cb"].append(d))
    await asyncio.sleep(0.5)
    print("SUBSCRIBE frames received by servers:", subs)
    print("callback payloads:", got)
    await spot.close_connection(); await fut.close_connection(); await r.cleanup()
asyncio.run(main())

Output:

SUBSCRIBE frames received by servers: {'spot': ['btcusdt@aggTrade'], 'futures': []}
callback payloads: {'spot_cb': [{'stream': 'btcusdt@aggTrade', 'data': {'venue': 'spot'}}], 'fut_cb': [{'stream': 'btcusdt@aggTrade', 'data': {'venue': 'spot'}}]}

Expected

Each server receives its own SUBSCRIBE, and fut_cb receives {'venue': 'futures'}.

Impact

A process that follows the same symbol on Spot and Futures (basis or arbitrage monitoring, for example) gets Spot trades delivered to the Futures handler. Nothing is logged, and the payload shapes are close enough that it is easy to miss.

Suggested fix

Make both maps instance attributes created in the client's __init__ and use them wherever the globals are referenced today (subscribe filter, on, unsubscribe and the reconnect cleanup). Streams would then be deduplicated per client, which is what the pooling logic needs.

Dominant language
Python
Stars
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Avg merge
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Merged PRs (30d)
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First steps

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