Pipeline WebSocket Server

A FastAPI WebSocket server for running image processing pipelines with real-time progress updates.

Installation

git clone https://github.com/rewaifu/reline_ws
cd reline_ws
uv venv
uv pip install -e .

Running the server

source .venv/bin/activate
uvicorn app:app --host 0.0.0.0 --port 8000

How it works

1. Client connects to ws://localhost:8000/ws
2. Client sends a pipeline config as JSON
3. Server streams progress updates back
4. Client can cancel at any time

Only one pipeline can run at a time. If a client tries to connect while a pipeline is already running, it receives {"error": "worker busy"} and the connection closes.

---

Protocol

1. Send pipeline config (immediately after connecting)

[
  {
    "type": "folder_reader",
    "options": {
      "path": "input",
      "recursive": true,
      "mode": "rgb"
    }
  },
  {
    "type": "folder_writer",
    "options": {
      "path": "output",
      "format": "png"
    }
  }
]

2. Receive progress updates

{ "status": "running", "progress": 3, "data_len": 20 }

Field	Type	Description
status	string	Current state (see table below)
progress	int	Number of items processed so far
data_len	int	Total number of items

Status values

Status	Meaning
running	Pipeline is actively processing
done	All items processed successfully
cancelled	Stopped by client cancel request
error	Something went wrong (see error field)

3. Cancel (optional)

Send at any time to stop processing:

{ "action": "cancel" }

The server finishes the current item, then stops and sends a final cancelled message.

---

Error responses

Errors are sent as JSON before the connection closes:

{ "error": "worker busy" }

{ "error": "invalid json" }

{ "error": "invalid pipeline config: <details>" }