Django Table Change Logger

Quick Description

A python package which logs each change made to a Django model instance.

How to set up?

1. Add tablechangelogger to your INSTALLED_APPS
2. Run python manage.py migrate to initialize the model
3. Add TABLE_CHANGE_LOG_CONFIG to your settings.py file.
4. Additionaly, you can add TABLE_CHANGE_LOG_ENABLED to enable/disable table change logging. If not provided, the default value is True.

TABLE_CHANGE_LOG_CONFIG={
    'LOGGABLE_APPS': {
        'drivers': {
            'yourapp.models.Drivers': {
                'fields': ['driver_id', 'driver_name'],
                'callbacks': ('yourapp.app.callbacks.your_method_name')
            }
        },
        'cars': {
            'yourapp.models.Car': {
                'fields': ['license_plate', 'car_model'],
                'callbacks': ('yourapp.app.callbacks.your_method_name')
            }
        }
    },
    'TABLE_CHANGE_LOG_ENABLED': True
}

The keys of TABLE_CHANGE_LOG_CONFIG indicate your app label, while the nested mappings contain relative project path of your model mapped to a dictionary containing loggable fields of that respective model.

You can optionally specify a callback function path in your configuration. The best practice is to place your callback function in yourapp/callbacks.py

How it works?

• Obtains the TABLE_CHANGE_LOG_CONFIG from your respective settings file based on your environment.
• Initializes LOGGABLE_MODELS with the relative project paths of your models based on your configuration variable.
• Binds to pre_save signal of each loggable model
• For each field specified in the configuration variable, creates a record in the TableChangesLog model in each instance update.

Example

This section serves as a small example to demonstrate this package. The example takes the configuration above into account. Supposing you have a model called Driver and fields called latest_speed and driver_name and driver_id:

    driver = Driver.objects.last()
    driver.latest_speed = 5
    driver.save()  # tablechangelogger won't create a record since 'latest_speed' was not among the loggable fields

    driver.driver_name = 'John Doe'
    driver.save()  # a record with this driver is created

    # you can also use tablechangelogger.utils.get_model_name 
    model_name = driver._meta.model.__name__
    
    log = TableChangesLog.objects.filter(
        instance_id=driver.id, table_name=model_name)
    print(log.field_name, log.log.changes.get_field_new_value(log.field_name))  # prints 'driver_name, John Doe'

The model structure

This package provides you a django model which is called TableChangesLog; which tracks each change to a model instance specified in your configuration mapping. An example record is as follows:

{
 'app_label': 'drivers',
 'created_at': datetime.datetime(2019, 2, 22, 9, 1, 14, 619568, tzinfo=<UTC>),
 'field_name': 'latest_speed',
 'id': 1,
 'instance_id': 1,
 'table_name': 'Driver',
 'log': Log(changes=Change(new_value=100, old_value=75), created=<True|False>)
 }