mu2edaq-bigredbox

This is the Peter Shanahan inspired "BIG RED BOX"(tm)

Peter's box popped up when there was a major DAQ error, and was design to be big and red. Basically there is no question that there is a problem when this things appears.

So welcome to the mu2e version of the big red box.

This is more sophisticated than the original Shanahan design but still super simple to use.

A daemon runs the main application anywhere within the DAQ network (typically on a main node where run control or other applications are running). It then listens for BROADCAST UDP messages on a port.

If a message is broadcast in this manner (and here it can be from any place in the DAQ and the sender doesn't need to know anything about the reciever) it is picked up by the application, and a BIG RED BOX appears (with some additional info).

This is written using QT5 so it's portable. C, C++, and Python sender libraries are provided under libs/ along with three example programs (example-sender-c, example-sender-cpp, example-sender-py).

Features

• Listens for UDP broadcast messages on a configurable port (default: 37020)
• Displays a full-screen-style alert window with the system ID, timestamp, and error message
• Stays on top of other windows until acknowledged
• Rate-limits incoming messages to prevent flooding and unresponsiveness
• Caps the number of simultaneous alert windows
• Has a Pause box to turn off incoming messages
• Has a history of Errors Received and a counter which can open up a history so you can see what is going wrong.
• Runs as a background daemon with PID and log file management

Requirements

• Python 3.9+
• A display environment (X11 / DISPLAY variable set)

This does work with ssh forwarded X11 connections

Install

Create and activate a Python virtual environment, then install dependencies:

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt   # PyQt5>=5.15

Usage

# Start the alert listener as a background daemon
./start_daq_alert.sh

# Stop the daemon
./stop_daq_alert.sh

# Send a test alert to verify the GUI works
python3 demo_sender.py
python3 demo_sender.py --system-id "DAQ-NODE-03" --message "Readout buffer overflow"
python3 demo_sender.py --ip 192.168.1.255 --port 37020

The daemon writes logs to /tmp/daq_alert.log and stores its PID at /tmp/daq_alert.pid.

Alert payload format

External DAQ systems broadcast JSON over UDP:

{
  "system_id": "DAQ-NODE-01",
  "timestamp": "2026-03-11T14:32:00",
  "message": "Critical error in the data acquisition pipeline."
}

Architecture

UDP broadcast (port 37020)
        │
        ▼
UDPListenerThread   ← background QThread, emits message_received signal
        │
        ▼
  DAQAlertApp       ← throttles & caps windows, owns the Qt event loop
        │
        ▼
  AlertWindow       ← always-on-top PyQt5 window, tracks per-window history

Key files:

File	Purpose
daq_alert.py	Main application: UDP listener thread, alert window GUI, daemon lifecycle
demo_sender.py	Test utility to send mock alert messages
config.py	Shared constants (BROADCAST_PORT, MESSAGE_RATE_LIMIT, MAX_ALERT_WINDOWS, log/PID paths)
start_daq_alert.sh	Start the daemon in the background
stop_daq_alert.sh	Stop the running daemon
libs/	C, C++, and Python alert-sender libraries with CMake build system
libs/examples/	Example sender programs for each library interface
BUILD.md	Full build and installation instructions

Configuration

Edit config.py to change defaults:

Constant	Default	Description
BROADCAST_PORT	37020	UDP port to listen on
MESSAGE_RATE_LIMIT	10.0	Max messages accepted per second
MAX_ALERT_WINDOWS	2	Max simultaneous alert windows
LOG_FILE	/tmp/daq_alert.log	Daemon log path
PID_FILE	/tmp/daq_alert.pid	Daemon PID file path

Dismissing an alert

Click ACKNOWLEDGE, or press Enter, Esc, or Space.