Python Microsoft Fabric - Receiving events as they happen

Fabric can raise an event when something in its data changes, e.g. a value falls below a threshold, and a system outside Fabric often has to know about it right away. This page receives such events through a Kafka channel, and each event runs a service that passes it on.

How events reach a service

An eventstream sends events out through a destination, and a custom endpoint destination is one that speaks Kafka. A Kafka channel in Zato subscribes to it, and each event that arrives runs the channel's service. The destination can filter what it carries, so the channel receives only the events its service is for.

The channel

Under Connections → Message queues → Kafka → Channels, create the channel with the values from the Keys tab. The security definition is the same one the sending events page created, since the same app registration both sends and receives:

In enmasse YAML:

channel_kafka:
  - name: Fabric Alerts
    address: <namespace>.servicebus.windows.net:9093
    topic: <topic name>
    group_id: zato
    service: stock.notify-purchasing
    security: Fabric Events Token
    sasl_mechanism: OAUTHBEARER
    ssl: true

The service

The event arrives as the raw message, which is the JSON the eventstream sent. The service reads its fields and logs them, in the place where it would pass them on to the system that needs them.

# -*- coding: utf-8 -*-

# stdlib
import json

# Zato
from zato.server.service import Service

class NotifyPurchasing(Service):

    name = 'stock.notify-purchasing'

    def handle(self):

        # The event, as the eventstream sent it ..
        event = json.loads(self.request.raw_request)

        # .. its fields ..
        item_id = event['item_id']
        location = event['location']
        quantity = event['quantity']
        reorder_level = event['reorder_level']

        # .. and the log line the purchasing system reads.
        message = f'Stock below reorder level -> {item_id} at {location}, {quantity} left, reorder at {reorder_level}'
        self.logger.info(message)

What the server shows

When Fabric raises the event, the server log has the line within the same second:

See also

Learn more