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The Simulator itself consists of several different components:

  • The Vehicle Simulation model
  • An Event loop for generating vehicle events, run as either an Isolate or Web Worker depending upon the target platform.
  • An optional HTTP Server isolate for exposing a REST API with basic vehicle controls - starting/stopping the vehicle, updating the vehicle state, handling vehicle notifications, and querying vehicle events.

As the simulation state can not be shared directly across the isolates, the simulation model in the main isolate acts as the source of truth across the system:

  • Updates from the Event loop are applied to the simulation model periodically, in line with the event generation frequency: once per second by default.
  • The HTTP Server isolate maintains its own cached copy of the simulation state, which is updated with changes from the Event isolate, UI interaction, and the REST API. Changes received through the REST API are cached in the HTTP Server isolate and proxied back to the simulation model directly.
  • The UI in the main isolate is redrawn based on changes to the simulation model, triggered by UI interaction and updates from the Event loop or HTTP Server isolate.

An overview of the overall interactivity patterns for the different target platforms is provided below.


When running as a Web-based instance, the Event Loop is implemented in a dedicated Web Worker, analogous to the isolate-driven approach used by the other platforms. In this case, the Simulation is run entirely within the browser:

Web Worker-driven Simulation Flow


At present, it's not possible to serve the REST API from web-based instances, though a WebSocket implementation may be added in the future.

Other Target Platforms

For all other target platforms, the Event Loop is run in a dedicated isolate, and the REST API is directly exposed:

Isolate-driven Simulation Flow