WebSocket Flow

Current Implementation (Polling)

TradeEntry currently uses HTTP polling for real-time updates, as WebSocket was not required for the initial release.

How Polling Works

User triggers download
        │
        ▼
POST /api/bhav-downloader/download
        │
        ▼
FastAPI schedules BackgroundTask
        │
        ▼  (HTTP response sent immediately)
Frontend starts polling every 1500ms
        │
        ▼
GET /api/bhav-downloader/status
  Returns JSON from stats.json
        │
        ├── status == "RUNNING" → update progress bar, continue polling
        │
        └── status == "SUCCESS"/"FAILED" → stop polling, show result

stats.json Schema

{
  "status": "RUNNING",
  "progress": 45,
  "last_log": "Downloading F&O bhav for 2025-01-14...",
  "Logs": [
    {
      "message": "Starting update process...",
      "source": "BhavDownloader",
      "date": "2025-01-14",
      "timestamp": "05:30:00 PM"
    }
  ],
  "history": [
    {
      "date": "2025-01-14",
      "timestamp": "2025-01-14 05:35:00 PM",
      "status": "SUCCESS",
      "message": "Bhav copy ingested successfully."
    }
  ]
}

Planned: WebSocket Migration (v2.0)

In v2.0, polling will be replaced with WebSocket for:

• Bhav download progress
• Live option chain updates
• Price alerts

Planned WebSocket Events

Event	Direction	Payload
download.progress	Server → Client	{ progress, log, status }
download.complete	Server → Client	{ status, eq_date, fo_date }
price.alert	Server → Client	{ symbol, price, condition }
chain.update	Server → Client	Full option chain snapshot

Proposed Stack

• FastAPI WebSocket endpoints (/ws/download-progress)
• React useWebSocket hook
• Broadcasting via asyncio.Queue per client

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Implemented in: v2.0 (planned)