django-field-logger 0.1.0

A Django app for logging changes in model fields.

Django Field Logger

A Django app for logging changes in model fields.

How to set up?

1. Add fieldlogger to your INSTALLED_APPS

2. Run python manage.py migrate to initialize the model

3. Add FIELD_LOGGER_SETTINGS to your settings.py file.

FIELD_LOGGER_SETTINGS = {
    'ENCODER': 'path.to.your.json.Encoder', # (default: None)
    'DECODER': 'path.to.your.json.Decoder', # (default: None)
    'LOGGING_ENABLED': True, # (default: True)
    'FAIL_SILENTLY': True, # (default: True)
    'LOGGING_APPS': {
        'your_app': {
            'logging_enabled': True, # (default: True)
            'fail_silently': True, # (default: True)
            'models': {
                'YourModel': {
                    'logging_enabled': True, # (default: True)
                    'fail_silently': True, # (default: True)
                    'fields': ['field1', 'field2'], # (default: [])
                    'exclude_fields': ['field3', 'field4'], # (default: [])
                    'callbacks': [
                        lambda instance, fields, logs: print(instance, fields, logs),
                        'yourapp.app.callbacks.your_function_name'
                    ], # (default: [])
                },
            },
            'callbacks': [
                lambda instances, fields, logs: print(instances, fields, logs),
                'yourapp.app.callbacks.your_function_name'
            ], # (default: [])
        },
    },
    'CALLBACKS': [
        lambda instance, fields, logs: print(instance, fields, logs),
        'yourapp.app.callbacks.your_function_name'
    ], # (default: [])
}

• ENCODER and DECODER are optional. If you want to encode/decode your model instance fields, you can specify your encoder/decoder classes here. Your encoder/decoder classes must be subclasses of json.JSONEncoder and json.JSONDecoder respectively.

• LOGGING_ENABLED is optional. If you want to disable logging globally, you can set this to False.

• FAIL_SILENTLY is optional. If it is set to False, exceptions will be raised if the callback function fails.

• LOGGING_APPS apps to be logged.

  • models models to be logged.

    • fields is optional. If you want to log only specific fields, you can specify them here. If you want to log all fields, you can use __all__ as a value.

    • exclude_fields is optional. If fields is not specified, all fields in the model will be logged except the ones specified here.

    • callbacks is optional. If you want to add a callback function to be called after logging all models in all apps, you can add it here. Callback functions must be callable objects. You can optionally specify a callback function path in your configuration. The best practice is to place your callback function in yourapp/callbacks.py. Callback functions must have three parameters as follows:

      # callback as a named function
      def your_callback(instance, fields, logs):
          # your code here
      
      # callback as a lambda function
      lambda instance, fields, logs: # your code here

      • instance the model instance that is being logged.

      • fields list of fields that are being logged.

      • logs dict of logs that are being created. The key is the field name and the value is the FieldLog instance.

How it works?

• Obtains the FIELD_LOGGER_SETTINGS from your respective settings file based on your environment.

• Initializes LOGGING_APPS 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 FieldLog model for each instance update.

Example

This section serves as a small example to demonstrate how to use this package.

Supposing you have this configuration in your settings.py file:

FIELD_LOGGER_SETTINGS = {
    'LOGGING_APPS': {
        'drivers': {
            'models': {
                'Driver': {
                    'fields': ['driver_name']
                },
            },
        },
    },
}

Supposing you have a model called Driver with fields called latest_speed, driver_name, driver_id:

driver = Driver.objects.last()
driver.latest_speed = 5
driver.save()  # fieldlogger 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

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

instance_id = driver.id
app_label = driver._meta.app_label
model_name = driver._meta.model_name

log = FieldLog.objects.filter(instance_id=instance_id, app_label=app_label, table_name=model).last()
print(log.field, log.old_value, log.new_value)  # prints: driver_name John Doe Jane Doe

Callback example

Supposing you have this function in yourapp/callbacks.py which sets the extra_data field of the FieldLog model:

def set_extra_data_for_driver_name(instance, fields, logs):
    log = logs.get('driver_name')
    if log:
        log.extra_data = {
            'name_length': len(log.new_value)
        }
        log.save()

Then you can add this callback function to your configuration like this:

FIELD_LOGGER_SETTINGS = {
    'LOGGING_APPS': {
        'drivers': {
            'models': {
                'Driver': {
                    'fields': ['driver_name'],
                    'callbacks': [
                        'yourapp.callbacks.set_extra_data_for_driver_name'
                    ]
                },
            },
        },
    },
}

Note

You can also add lambda functions to your callbacks

The model structure

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

{
    'id': 2,
    'app_label': 'drivers',
    'model': 'driver',
    'instance_id': 1,
    'field': 'latest_speed',
    'timestamp': datetime.datetime(2024, 1, 16, 9, 1, 14, 619568, tzinfo=<UTC>),
    'old_value': 'John Doe',
    'new_value': 'Jane Doe',
    'extra_data': {}, # this is a JSONField, you can store any extra data here using callbacks or by overriding it directly
    'created': False, # this is a boolean field, if it is True, it means that instance is a newly created instance
}

Additionally, FieldLog model provides the following properties:

• model: returns the model class of the instance that is being logged.

• instance: returns the instance that is being logged.

• previous_log: returns the previous log of the instance that is being logged.

The FieldLoggerMixin

This package provides you a mixin class which is called FieldLoggerMixin. This mixin class provides you the following property:

• fieldlog_set since the FieldLog model has not a direct relation to the model that is being logged, you can use this property to get the logs of the instance that is being logged.

  driver = Driver.objects.last()
  logs = driver.fieldlog_set.all()

MIT License

Copyright (c) 2024 Sergio Rodríguez

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.