Node Software Processes and Inter-Process Communication

Due to document length constraints, this document is a reference outline. For detailed specifications, see:

• Section 4: Software Process Architecture , Process model, five independent processes (FastAPI, Antenna Control, DSP, Telemetry Router, Health Monitor)
• Section 5: Inter-Process Communication (IPC) Buses , Control bus (ZeroMQ), Status/Telemetry bus, DSP-to-Router stream, Antenna feedback loop

Key Concepts

Five independent processes communicate via dedicated IPC buses:

1. FastAPI Control Server (Python, port 8080)

   • Listens for REST calls from central
   • Publishes control messages to all subsystems
   • Collects status from each worker
   • Exposes /status, /capabilities, /metrics endpoints

2. Antenna Control Daemon (Python or C++)

   • Receives az/el or coordinate-based pointing requests
   • Converts to device commands (FPGA weights, motor PWM, etc.)
   • Reports actual position and motor status

3. DSP Pipeline (C++/GNU Radio)

   • Continuous high-rate IQ processing (40 MSPS)
   • Outputs decoded frames, lock metrics, Doppler tracking

4. Telemetry Router (Python or C++)

   • Extracts frames from the active DSP bit stream
   • Applies field schemas and payload typing for configured payloads
   • Emits telemetry events to output port 9002 as raw frame bytes or schema-backed JSON objects

5. Health Monitor (Python)

   • Collects CPU, memory, temperature, FPGA load
   • Publishes to Prometheus metrics(:9003) and status bus

IPC Buses:

• Control Bus (port 5555, ZeroMQ Pub-Sub): FastAPI → all workers
• Status Bus (port 5556, ZeroMQ Push-Pull): Workers → FastAPI
• DSP-to-Router Stream (Unix socket): High-bandwidth frame transfer
• Antenna Feedback: Position and encoder updates back to FastAPI

Design principle: Decouple API path from DSP path. DSP restarts don't kill the HTTP server.

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Full details in node-specific documents: See Node-NetworkPorts for port allocation, Node-ConfigurationProtocols for control messaging.