[Yandex Cloud documentation](../../index.md) > [Yandex Serverless Containers](../index.md) > [Step-by-step guides](index.md) > Creating a trigger > Creating a trigger for Yandex IoT Core > Broker

# Creating a trigger that will send messages to a container in Serverless Containers from a Yandex IoT Core broker topic

Create a [trigger](../concepts/trigger/iot-core-trigger.md) for a Yandex IoT Core broker topic and process message copies using a [container](../concepts/container.md) in Serverless Containers.

{% note warning %}

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

{% endnote %}

## Getting started {#before-begin}

To create a trigger, you will need:

* Container the trigger will invoke. If you do not have a container:

    * [Create a container](create.md).
    * [Create a container revision](manage-revision.md#create).

* Optionally, a [dead-letter queue](../concepts/dlq.md) for unprocessed messages from the container. If you do not have a queue, [create one](../../message-queue/operations/message-queue-new-queue.md).

* [Service account](../../iam/concepts/users/service-accounts.md) with permissions to invoke the container and, optionally, write 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](../../iam/operations/sa/create.md).

* [Broker](../../iot-core/concepts/index.md#broker) whose topic the trigger will receive message copies from. If you do not have a broker, [create one](../../iot-core/operations/broker/broker-create.md).

## Creating a trigger {#trigger-create}

{% note info %}

The trigger is initiated within five minutes after it is created.

{% endnote %}

{% list tabs group=instructions %}

- Management console {#console}

    1. In the [management console](https://console.yandex.cloud), select the folder where you want to create a trigger.

    1. Navigate to **Serverless Containers**.

    1. In the left-hand panel, select ![image](../../_assets/console-icons/gear-play.svg) **Triggers**.

    1. Click **Create trigger**.

    1. 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 `Container`.

    1. Under **IoT Core message settings**:
      
        * In the **Broker** field, specify the broker.
        * Optionally, in the **MQTT topic** field, specify an MQTT topic. If no MQTT topic is set, the trigger will fire for all broker topics.

    1. 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 within the specified wait time period and sends them to the container. The number of messages cannot exceed the specified batch size.
    
    1. Under **Container settings**, select a container and specify a [service account](../../iam/concepts/users/service-accounts.md) that will invoke it.

    1. Optionally, under **Repeat request settings**:

        * In the **Interval** field, specify the time to wait before retrying the container invocation if it 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 moves a message to the dead-letter queue. The values may range from 1 to 5. The default value is 1.

    1. Optionally, under **Dead Letter Queue settings**, select a dead-letter queue and a service account with write permissions for that queue.

    1. Click **Create trigger**.

- CLI {#cli}

    If you do not have the Yandex Cloud CLI yet, [install and initialize it](../../cli/quickstart.md#install).

    The folder used by default is the one specified when [creating](../../cli/operations/profile/profile-create.md) the CLI profile. To change the default folder, use the `yc config set folder-id <folder_ID>` command. You can also specify a different folder for any command using `--folder-name` or `--folder-id`. If you access a resource by its name, the search will be limited to the default folder. If you access a resource by its ID, the search will be global, i.e., through all folders based on access permissions.

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

    ```bash
    yc serverless trigger create iot-broker \
      --name <trigger_name> \
      --broker-id <broker_ID> \
      --mqtt-topic '<MQTT_topic>' \
      --batch-size <message_batch_size> \
      --batch-cutoff <maximum_wait_time> \
      --invoke-container-id <container_ID> \
      --invoke-container-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](../../iot-core/operations/broker/broker-list.md).
    * `--mqtt-topic`: MQTT topic you want to create a trigger for. This is an optional setting. If you skip it, 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 container. The number of messages cannot exceed `batch-size`.

    * `--invoke-container-id`: Container ID.
    * `--invoke-container-service-account-id`: ID of the service account with permissions to invoke the container.
    * `--retry-attempts`: Number of invocation retries before the trigger moves a message to the dead-letter queue. This is an optional setting. The values may range from 1 to 5. The default value is 1.
    * `--retry-interval`: Time to wait before retrying the container invocation if it fails. This is an optional setting. 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 setting.
    * `--dlq-service-account-id`: ID of the service account with write permissions for the dead-letter queue. This is an optional setting.

    Result:

    ```text
    id: a1s5msktijh2********
    folder_id: b1gmit33hgh2********
    created_at: "2022-10-24T15:19:15.353909857Z"
    name: iot-broker-trigger
    rule:
      iot_broker_message:
        broker_id: arenou2oj4h2********
        mqtt_topic: topic-for-broker
        batch_settings:
          size: "1"
          cutoff: 0s
        invoke_container:
          container_id: bba5jb38o8h2********
          service_account_id: aje3932acdh2********
          retry_settings:
            retry_attempts: "1"
            interval: 10s
    status: ACTIVE
    ```

- API {#api}

  To create a trigger for Yandex IoT Core, use the [create](../triggers/api-ref/Trigger/create.md) REST API method for the [Trigger](../triggers/api-ref/Trigger/index.md) resource or the [TriggerService/Create](../triggers/api-ref/grpc/Trigger/create.md) gRPC API call.

{% endlist %}

## Checking the result {#check-result}

Check that the trigger works correctly. To do this, view [container logs](../concepts/logs.md) that show information on invocations.

## Useful links {#see-also}

* [Creating a trigger that sends messages to Cloud Functions from a Yandex IoT Core registry or device topic](../../functions/operations/trigger/iot-core-trigger-create.md)
* [Creating a trigger that sends messages to WebSocket connections from a Yandex IoT Core broker topic](../../api-gateway/operations/trigger/iot-core-trigger-broker-create.md)