django-collect-offline 0.2.49

Configure a model for offline-use:

To include a model for offline-use declare the model with BaseUuidModel from edc-base, define the natural_key method and the model manager method get_by_natural_key and add the HistoricalRecords manager from edc-base.

For example the base class for all CRFs in a module might look like this:

from edc_model.models import BaseUuidModel, HistoricalRecords

from .visit import Visit

class CrfModel(BaseUuidModel):

    visit = models.OneToOneField(Visit)

    objects = CrfModelManager()

    history = HistoricalRecords()

    def natural_key(self):
        return (self.visit.natural_key(), )
    natural_key.dependencies = ['myapp.visit']

Add a model to the site global

In your app, add module offline_models.py.

# offline_models.py

from django_collect_offline.site_offline_models import site_offline_models
from django_collect_offline.offline_model import OfflineModel

offline_models = [
    'my_app.CrfModel',
]

site_offline_models.register(offline_models, OfflineModel)

View models registered for synchronization

from django_collect_offline.site_offline_models import site_offline_models

# list all models in app 'bcpp_household' set for offline-use
models = site_offline_models.site_models('bcpp_household', sync=True)

# list all models in app 'bcpp_household' NOT set for offline-use
models = site_offline_models.site_models('bcpp_household', offline=False)

# list all models in app 'bcpp_household' not set for offline-use, excluding the "historical" models
offline_models = [m.model._meta.label_lower for m in models if 'historical' not in m.model_name]

To create the model list for an apps offline_models.py, open a shell and list all models not yet registered for offline-use:

models = site_offline_models.site_models('bcpp_household', offline=False)
[m.model._meta.label_lower for m in models if 'historical' not in m.model_name]

About Offline-use

The offline model approach is limited and only transfers data one-way and always toward a central server or parent node. Many client nodes may push data to their server node.

Getting data from the field

We use django-collect-offline in Django projects deployed to low-resourced remote communities where there is no reliable internet, public or private network. Our Research Assistants collect participant data in households, mobile tents and remote clinics. The Research Assistants enter data directly into their offline laptops. Once back online, data is pushed to the community-server and later to the central-server.

Our research also involves collecting blood specimens that need to get to our community clinic within an hour or two from time of collection. Research Assistants stay out in the field on shift for 6 hours or more. So we send a driver to fetch specimens and data from the Research Assistant in the field. The driver has a middleman laptop that pulls all pending data from the Research Assistant’s laptop. The driver and the Research Assistant then reconcile specimens and requisition data against the middleman data and the physical specimen. (Note: we requisition and label specimens in the field through the app). The driver then returns to the community clinic, pushes data onto the community-server and delivers all the specimens. The Lab Assistant then reconciles the specimens and requisition data against the community-server data and the physical specimen.

Data Flow

django-collect-offline uses either the REST API or FILE transfer:

• field client —REST—> community server

• field client —REST—> middleman (and modelre inspector) —REST—> community server

• site server —FILE—> central server