Implementing Checkout Times for Attendees on Open Event Server

As of this writing, Open Event Server did not have the functionality to add, manipulate and delete checkout times of attendees. Event organizers should have access to log and update attendee checkout times. So it was decided to implement this functionality in the server. This boiled down to having an additional attribute checkout_times in the ticket holder model of the server.

So the first step was to add a string column named checkout_times in the ticket holder database model, since this was going to be a place for comma-separated values (CSV) of attendee checkout times. An additional boolean attribute named is_checked_out was also added to convey whether an attendee has checked out or not. After the addition of these attributes in the model, we saved the file and performed the required database migration:

To create the migration file for the above changes:

$ python db migrate

To upgrade the database instance:

$ python db upgrade

Once the migration was done, the API schema file was modified accordingly:

class AttendeeSchemaPublic(SoftDeletionSchema):
    Api schema for Ticket Holder Model
    checkout_times = fields.Str(allow_none=True)  # ←
    is_checked_out = fields.Boolean()  # ←

After the schema change, the attendees API file had to have code to incorporate these new fields. The way it works is that when we receive an update request on the server, we add the current time in the checkout times CSV to indicate a checkout time, so the checkout times field is essentially read-only:

from datetime import datetime
class AttendeeDetail(ResourceDetail):
    def before_update_object(self, obj, data, kwargs):
        if 'is_checked_out' in data and data['is_checked_out']:
            if obj.checkout_times and data['checkout_times'] not in \
                data['checkout_times'] = '{},{},{}'.format(


This completes the implementation of checkout times, so now organizers can process attendee checkouts on the server with ease.