Cog Runtime

Caution

This project is experimental and should not be handled near open flame.

Alt-core Cog runtime implementation.

The original Cog seeks to be a great developer tool and also an arguably great production runtime. Cog runtime is focused on being a fantastic production runtime only.

How is cog-runtime formed?

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sequenceDiagram
    participant r8
    participant server as cog-server
    participant runner as coglet
    participant predictor as Predictor
    r8->>server: Boot
    activate server
    server->>runner: exec("python3", ...)
    activate runner
    runner<<->>predictor: setup()
    activate predictor
    runner--)server: SIGHUP (output)
    runner--)server: SIGUSR1 (ready)
    server->>runner: read("setup-result.json")
    r8->>server: GET /health-check
    r8->>server: POST /predictions
    server->>runner: write("request-{id}.json")
    runner--)server: SIGUSR2 (busy)
    runner<<->>predictor: predict()
    deactivate predictor
    runner--)server: SIGHUP (output)
    runner--)server: SIGUSR1 (ready)
    server->>runner: read("response-{id}.json")
    deactivate runner
    server->>r8: POST /webhook
    deactivate server

This sequence is simplified, but the rough idea is that the Replicate platform (r8) depends on cog-server to provide an HTTP API in front of a coglet that communicates via files and signals.

cog-server

Go-based HTTP server that knows how to spawn and communicate with coglet.

coglet

Python-based model runner with zero dependencies outside of the standard library. The same in-process API provided by Cog is available, e.g.:

from cog import BasePredictor, Input

class MyPredictor(BasePredictor):
    def predict(self, n=Input(default="how many", ge=1, le=100)) -> str:
        return "ok" * n

In addition to simple cases like the above, the runner is async by default and supports continuous batching.

Communication with the cog-server parent process is managed via input and output files and the following signals:

• SIGUSR1 model is ready
• SIGUSR2 model is busy
• SIGHUP output is available