Koherent

What is Koherent?

Koherent is a python library that allows you to integrated based audit logging into your application. It thinly wraps the django-simple-history library, and provides a simple interface for logging and reverting changes to your models.

Note: This library is still heavily tied to the Arkitekt Framework. We are working on making it more generic.

What do we track?

By default (soon to be configurable), we track the following parameters:

• user - The user who made the change
• app - The application that made the change (if present)
• assignation_id - In which context the change was made (if present)
• action - The action that was performed (create, update, delete)
• model - The model that was changed

What is an assignation?

An assignation ID (or more commonly known as a context_id or correlation_id) is a unique identifier that is used to group changes together. FOr example, if you have a Task model, and you want to track all changes to a specific task, you would use the Task's ID as the assignation ID. This allows you to easily track all changes to a specific task, and revert them if necessary.

How do I use it?

Koherent is a Django Libary, so you will have to add it to your INSTALLED_APPS in your settings.py file.

INSTALLED_APPS = [
    ...
    'koherent',
    ...
]

Model Setup

Then in your models, you will need to add the KoherentHistoryModel mixin to your model.

from koherent.fields import HistoryField, HistoricForeignKey
import koherent.signal # This is required to register the signal handlers

class MyModel(KoherentHistoryModel):
    your_field = models.CharField(max_length=255)
    history = HistoryField()
    ...

Strawberry Setup

Koherent is designed to work with Strawberry, so you will need to add its extension to your schema.

import strawberry_django
from koherent.strawberry.extension import KoherentExtension
from app import models

@strawberry_django.type(models.MyModel)
class MyModel:
    id: strawberry.ID
    name: str

@strawberry.type
class Query:

    @strawberry_django.field
    def create_model(self, info, your_field: str) -> MyModel:
        model = models.MyModel.objects.create(your_field=your_field)
        # This will create a new history entry (by sending a signal)
        # bound to the current user and the assignation id

        return model

    @strawberry_django.field
    def update_model(self, info, id: strawberry.ID, your_field: str) -> MyModel:
        model = models.MyModel.objects.get(id=id)
        model.your_field = your_field
        model.save()
        # This will create a new history entry (by sending a signal)
        # bound to the current user and the assignation id

        return model



schema = strawberry.Schema(query=Query, extensions=[KoherentExtension])

GraphQL Setup

Currently we require that you use the Kante GraphQL library, as it provides the assignation_id and user context required for the audit logging. We are soon going to make this more generic.

ASSIGNATION_ID in the Arkitekt Framework

In the Arkitekt Framework, we use the assignation_id to track changes that are done by an app when a user is calling that app through an Arkitekt Rekuest. This allows us to track all changes that are done by a specific Rekuest, and revert them if necessary.

from arkitekt import register
from service.generated_api import create_model, update_model, delete_model, MyModel


@register
def do_some_transactions(name: str) -> MyModel:
    """ Do some transactions """
    # Within this function, all api requests will have the assignatio-id header
    # set to the same value. This allows us to track all changes that are done

    z = create_model(name=name)

    f = update_model(id=z.id, name="New Name") # tracked with the same assignation_id
    
    return f