Krashanoff/websockets

[krashanoff]

Continuation of #63. Begins implementation of a websocket handler and most of the grading runner subsystem. Right now, it looks a little something like this:

sequenceDiagram
  actor User
  User->>Handler: Upload work
  activate Handler
  Handler->>Runner: Run a job
  activate Runner
  Handler-->>User: OK
  deactivate Handler
  User->>Handler: Get live results
  activate Handler
  Handler->>Runner: Subscribe to job
  loop for each test case
    Runner-->>Handler: Result
    Handler-->>User: Test case info
  end
  Runner->>DB: Writeback all results
  activate DB
  DB-->>Runner: Complete
  deactivate DB
  Runner-->>Handler: Final score
  deactivate Runner
  Handler-->>User: Terminate connection
  deactivate Handler

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Basically, SPMC parallelism over websockets. There's the issue of the server terminating before writing back results, right now, but I think that as long as this is well-documented, we can come back to it in the near future, before much more is built on the runner. The hierarchy looks like:

classDiagram
  Runner
  JobManager
  Handler
  Handler "1" o-- "1" Context
  Context "*" o-- "1" Runner
  Runner "1" o-- "*" JobManager

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[1strangequark]

I looked this over and did not see any immediate issues with it. It looks good, I think.

[krashanoff]

It's going to complain about how I'm not checking for nil in my job spawning loop but I think this is fine to merge now contingent on #68 to work out any kinks.

[krashanoff]

Rebased on main. Basic functionality for websockets is there. Now just have to bind it to our frontend.