CMSW Main Application (cmsw_main_app.py)

Overview

The CMSW main application is responsible for launching:

All asynchronous CMSW background tasks (polling, safety checks, etc.)
Optionally, the CMSW REST API (FastAPI + Uvicorn)
A unified shutdown mechanism for the tasks and the API

It uses an asynchronous event loop to run multiple cooperative tasks and supports clean shutdown via:

Ctrl+C (SIGINT)
SIGTERM (service stop)
POST /shutdown (if the API is enabled)

Usage

Set up the virtual environment with all required dependencies by following the instructions in CMSW Installation Instructions.
Activate the virtual environment and run the CMSW main application:

source .venv/bin/activate
cd src/ska-low-sps-cabinet-cmsw
python cmsw_main_app.py

Command-Line Arguments

The application may be started in two modes:

1. Standard Mode (API Enabled)

This is the default behavior. Run:

python cmsw_main_app.py

This launches:

CMSW tasks (PDU sensor polling, cooling system sensor polling, safety model, fault detection, low power mode)
The REST API defined in cmsw_api.py

2. Headless Mode (No API)

To run CMSW without the API:

python cmsw_main_app.py --no-api

In this mode:

Only background CMSW tasks are started
No FastAPI/Uvicorn server is launched
Shutdown must be triggered by Ctrl+C or external SIGTERM

Argument Summary

Argument	Description
`--no-api`	Disable REST API server
`--placeholder`	Force-enable the REST API

Background Tasks

The following asynchronous CMSW tasks are launched at runtime:

pdu_task
cooling_task
safety_task
fault_task
low_power_task

Each task runs periodically using the intervals defined in config.yaml:

cmsw:
  polling_intervals:
    sensor_polling: 5
    safety_model: 10
    fault_detection: 20
    low_power_mode: 30

These tasks run concurrently inside the asyncio event loop and share state via shared_state.py.

For detailed information about sensor polling capabilities, see Sensor Polling.

API Integration

If API mode is enabled, Uvicorn and FastAPI are launched inside the same event loop as CMSW tasks. This ensures immediate access to live CMSW data via HTTP.

API configuration is stored in config.yaml:

cmsw:
  api:
    host: "0.0.0.0"
    port: 8082

API calls supported currently:

Get readings_dict (use -s option for silent output without progress bar):

curl -s <host>:<port>/readings

Shutdown CMSW (-X option is for specifying API request type, e.g. POST. Default is GET.):

curl -X POST http://<host>:<port>/shutdown

Shutdown Behaviour

The application shuts down cleanly when:

Ctrl+C is pressed
SIGTERM is received
shutdown_event is triggered by the API

Shutdown sequence:

API server is stopped (if active)
All tasks are cancelled
All asyncio tasks are awaited for proper cleanup
Event loop exits

This ensures that Modbus, SNMP, and other future subsystems can perform safe teardown.

Design Notes

The application runs with asyncio.run to ensure isolation of the event loop.
Shutdown is coordinated using a global shutdown_event imported from shared_state.py.
Running the API and the CMSW task engine in the same process avoids synchronization problems and maintains consistency.