Processes and Threads

A SIC application is a collection of processes and threads that run across multiple devices, coordinated through Redis messaging.

Process Architecture

SIC applications consist of two main types of processes:

Client-side (SIC Application)

  • Runs the main application logic

  • Contains Connectors and DeviceManagers

  • Orchestrates component interactions through Redis

  • Handles graceful shutdown and cleanup

Server-side (Component Managers)

  • Manages component lifecycle on each device

  • Started by commands like run-face-detection or by DeviceManagers

  • Can run locally (Desktop) or remotely (NAO, Pepper, etc.)

  • Each Component Manager can host multiple Components but only of specified types.

Each process gets its own RedisConnection instance, which is used to communicate with the Redis server.

Thread Types

Redis Subscriber Threads

These threads listen to Redis channels and handle incoming messages:

Component Handler Threads

  • Handle incoming messages and requests for components

  • Created by register_message_handler() and register_request_handler()

  • Named like “ComponentName_message_handler” or “ComponentName_request_handler”

  • Execute component’s on_message() and on_request() methods

Application Callback Threads

  • Created when applications register callbacks with register_callback()

  • Process component output before sending to other components

  • Named like “ComponentEndpoint_callback”

  • Allow custom processing of component data

Request-Reply Threads

  • Created temporarily when sending requests via request()

  • Subscribe to reply channels and wait for responses

  • Automatically cleaned up after receiving replies

Component Main Threads

  • Created when a ComponentManager starts a Component

  • Some such as Sensors enter a loop that continuously produces output; Others just initialize an API (such as GPT, Dialogflow)

Device Management Threads

SSH Monitor Threads

  • Created by DeviceManagers for remote devices

  • Monitor SSH connections and remote process status

  • Detect when remote processes stop unexpectedly

Local Component Manager Threads

  • For local devices (Desktop, Franka), Component Managers run in threads

  • Run as daemon threads to avoid blocking main application

Shutdown Process

Application Shutdown Process