# Task Queue

Tryton provides a way to run asynchronously some tasks. You must activate the worker in the `queue` section of the configuration and run the worker manager otherwise the tasks will be run at the end of the transaction.

A task is the parameters that defines how to call a method from a `trytond.model.Model`. This include the `trytond.transaction.Transaction.context`, the `trytond.transaction.Transaction.user` and the arguments. The first argument of the method must be an instance or a list of instances of `trytond.model.Model`. This other arguments must be JSON-ifiable.

A task is pushed into the `queue` by calling the desired method on the `trytond.model.Model.__queue__`. This stores in the queue all the current parameters of the call and it will be execute by a worker or at the end of the transaction if no worker is configured. The following `trytond.transaction.Transaction.context` keys are used as parameters for the queue:

> - `queue_name`: The name of the queue. Default value is `default`.

> - `queue_scheduled_at`: A `datetime.timedelta` to add to current time to define when the task should be started. Default value is `None` which means directly.

> - `queue_expected_at`: A `datetime.timedelta` to add to current time to define when the task should be finished. Default value is `None` which means as soon as possible.

Warning

There is no access right verification during the execution of the task.

Example:

    from trytond.model import Model

    class MyModel(Model):
        "My Model"
        __name__ = 'my_model'

        @classmethod
        def launch(cls, records):
            for record in records:
                cls.__queue__.process(record, 42)

        def process(self, value):
            self.value = value