architecture.md

Architecture of Kelvin

Kelvin consists of several interconnected services:

• Kelvin web
  • Django 4 application that provides a REST API and also a set of user-facing web pages and templates
  • It renders some part of the web using a JavaScript frontend
• JavaScript frontend
  • Reactive frontend implemented using Svelte 3, which is rendered into a single JS and CSS file and served by the Django app.
• PostgreSQL database
  • Provides persistent storage of users, classes, subjects etc. for the web
• Redis
  • Provides a temporary (non-persistent) cache used for e.g. storing code plagiarism detection check results

The web also uses RQ (Redis) queues for executing various jobs. There are three queues:

• default queue performs jobs related to code plagiarism detection
• evaluator queue performs evaluations of code submitted by students
  • The evaluation logic is implemented in the evaluator directory
  • It uses Docker internally to perform various evaluation pipelines
• cuda queue also performs evaluation, but it should be used for code that needs an NVIDIA GPU

Here is a simple diagram that describes the architecture:

architecture-beta
    group server(server)[Server]
    
    service django(server)[Django] in server
    service frontend(internet)[JS frontend] in server
    frontend:R --> L:django
    
    service db(database)[PostgreSQL]
    django:T <--> B:db
    
    service redis(database)[Redis]
    django:R <--> L:redis
    
    service worker(server)[Queue worker N]
    worker:T -- B:django
    worker:R <--> B:redis

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Directory structure

kelvin
├── api - REST API of the backend
├── evaluator - evaluation pipelines for checking submitted code
│   ├── images - docker images for custom pipeline actions
│   └── pipelines.py - integrated pipeline actions - e.g. Docker evaluation
│── frontend - JavaScript frontend
├── kelvin - base configuration of the application
├── survey - module for creating surveys defined in yaml
└── web - web interface for the kelvin web app