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Creating a trigger for a broker topic

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Updated at May 13, 2025

Create a trigger for an Yandex IoT Core broker topic and process message copies using a Cloud Functions function.

Warning

The trigger must be in the same cloud as the broker whose topic it reads messages from.

Getting started

To create a trigger, you need:

  • A function that the trigger will invoke. If you do not have a function:

  • (Optional) A dead-letter queue where messages that could not be processed by a function will be redirected. If you do not have a queue, create one.

  • Service accounts with permissions to invoke the function and (optionally) write messages to the dead-letter queue. You can use the same service account or different ones. If you do not have a service account, create one.

  • Broker from the topic of which the trigger will collect message copies. If you do not have a broker, create one.

Creating a trigger

Note

The trigger is initiated within 5 minutes of being created.

  1. In the management console, select the folder where you want to create a trigger.

  2. Select Cloud Functions.

  3. In the left-hand panel, select Triggers.

  4. Click Create trigger.

  5. Under Basic settings:

    • Enter a name and description for the trigger.
    • In the Type field, select IoT Core (broker).
    • In the Launched resource field, select Function.

  6. Under IoT Core message settings:

    • In the Broker field, specify the broker.
    • (Optional) In the MQTT topic field, specify an MQTT topic. If no MQTT topic is set, the trigger fires for all broker topics.

  7. Under Batch message settings, specify:

    • Waiting time, s​. The values may range from 1 to 60 seconds. The default value is 1 second.
    • Batch size​. The values may range from 1 to 100. The default value is 1.

    The trigger groups messages for a period of time not exceeding the specified timeout and sends them to a function. The number of messages cannot exceed the specified batch size.

  8. Under Function settings, select a function and specify:

  9. Optionally, under Repeat request settings:

    • In the Interval field, specify the time after which the function will be invoked again if the current attempt fails. The values may range from 10 to 60 seconds. The default value is 10 seconds.
    • In the Number of attempts field, specify the number of invocation retries before the trigger sends a message to the dead letter queue. The values may range from 1 to 5. The default value is 1.

  10. Optionally, under Dead Letter Queue settings, select the dead-letter queue and the service account with write permissions for this queue.

  11. Click Create trigger.

If you do not have the Yandex Cloud (CLI) command line interface yet, install and initialize it.

The folder specified when creating the CLI profile is used by default. To change the default folder, use the yc config set folder-id <folder_ID> command. You can specify a different folder using the --folder-name or --folder-id parameter.

To create a trigger that invokes a function, run this command:

yc serverless trigger create iot-broker \
  --name <trigger_name> \
  --broker-id <broker_ID> \
  --mqtt-topic '<MQTT_topic>' \
  --batch-size <message_group_size> \
  --batch-cutoff <maximum_timeout> \
  --invoke-function-id <function_ID> \
  --invoke-function-service-account-id <service_account_ID> \
  --retry-attempts <number_of_retry_attempts> \
  --retry-interval <interval_between_retry_attempts> \
  --dlq-queue-id <dead-letter_queue_ID> \
  --dlq-service-account-id <service_account_ID>

Where:

  • --name: Trigger name.
  • --broker-id: Broker ID.
  • --mqtt-topic: MQTT topic you want to create a trigger for. This is an optional parameter. If this parameter is skipped, the trigger will fire for all broker topics.
  • --batch-size: Size of the message batch from MQTT topics. This is an optional parameter. The values may range from 1 to 10. The default value is 1.
  • --batch-cutoff: Maximum waiting time. This is an optional parameter. The values may range from 1 to 60 seconds. The default value is 1 second. The trigger groups messages for a period not exceeding batch-cutoff and sends them to a function. The number of messages cannot exceed batch-size.
  • --invoke-function-id: Function ID.
  • --invoke-function-service-account-id: ID of the service account with permissions to call the function.
  • --retry-attempts: Number of invocation retries before the trigger sends a message to the dead-letter queue. This is an optional parameter. The values may range from 1 to 5. The default value is 1.
  • --retry-interval: Time after which the function will be invoked again if the current attempt fails. This is an optional parameter. The values may range from 10 to 60 seconds. The default value is 10 seconds.
  • --dlq-queue-id: Dead-letter queue ID. This is an optional parameter.
  • --dlq-service-account-id: ID of the service account with write permissions for the dead-letter queue. This is an optional parameter.

Result:

id: a1sl0mkmimfj********
folder_id: b1g88tflru0e********
created_at: "2019-09-25T13:54:35.654935Z"
name: iot-broker-trigger
rule:
  iot_broker_message:
    broker_id: arenou2oj4**********
    mqtt_topic: topic-for-broker
    batch_settings:
      size: "1"
      cutoff: 0s
    invoke_function:
      function_id: d4eofc7n0m03********
      function_tag: $latest
      service_account_id: aje3932acd0c********
      retry_settings:
        retry_attempts: "1"
        interval: 10s
status: ACTIVE

To create a trigger for Yandex IoT Core, use the create REST API method for the Trigger resource or the TriggerService/Create gRPC API call.

Checking the result

Check that the trigger operates correctly. Do it by viewing function logs that present information on invocations.

See also

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