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IBM MQ Message Queue
====================

.. contents::
   :local:
   :depth: 2


IBM MQ Queue Provider
---------------------

Implemented by :class:`~airflow.providers.ibm.mq.queues.mq.IBMMQMessageQueueProvider`

The IBM MQ Queue Provider is a
:class:`~airflow.providers.common.messaging.providers.base_provider.BaseMessageQueueProvider`
that uses IBM MQ as the underlying message queue system.

It allows you to send and receive messages using IBM MQ queues in your Airflow workflows
via the common message queue interface
:class:`~airflow.providers.common.messaging.triggers.msg_queue.MessageQueueTrigger`.


.. include:: /../src/airflow/providers/ibm/mq/queues/mq.py
    :start-after: [START ibmmq_message_queue_provider_description]
    :end-before: [END ibmmq_message_queue_provider_description]


.. _howto/triggers:IBMMQMessageQueueTrigger:


IBM MQ Message Queue Trigger
----------------------------

Implemented by :class:`~airflow.providers.ibm.mq.triggers.mq.AwaitMessageTrigger`

Inherited from
:class:`~airflow.providers.common.messaging.triggers.msg_queue.MessageQueueTrigger`

Wait for a message in a queue
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. warning::

   ``AwaitMessageTrigger`` consumes IBM MQ messages with
   ``MQGMO_NO_SYNCPOINT``. This gives the trigger **at-most-once** delivery
   semantics: once IBM MQ returns a message, it is removed from the queue
   before Airflow emits the corresponding ``TriggerEvent``. If the trigger is
   canceled in that window, the message can be lost.

Below is an example of how you can configure an Airflow DAG to be triggered
by a message arriving in an IBM MQ queue.

.. exampleinclude:: /../tests/system/ibm/mq/example_dag_message_queue_trigger.py
    :language: python
    :start-after: [START howto_trigger_message_queue]
    :end-before: [END howto_trigger_message_queue]


How it works
------------

1. **IBM MQ Message Queue Trigger**
   The ``AwaitMessageTrigger`` listens for messages from an IBM MQ queue. It
   uses a non-transactional MQ get, so the integration is at-most-once rather
   than at-least-once.

2. **Asset and Watcher**
   The ``Asset`` abstracts the external entity, the IBM MQ queue in this example.
   The ``AssetWatcher`` associates a trigger with a name. This name helps you
   identify which trigger is associated with which asset.

3. **Event-Driven DAG**
   Instead of running on a fixed schedule, the DAG executes when the asset receives
   an update (for example, when a new message arrives in the queue).

For how to use the trigger, refer to the documentation of the
:ref:`Messaging Trigger <howto/trigger:MessageQueueTrigger>`.
