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

Create a [trigger](../concepts/trigger/iot-core-trigger.md) for a Yandex IoT Core device or registry 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 registry or device whose topic it reads messages from.

{% endnote %}

## Getting started {#before-begin}

To create a trigger, you will need:

* A container that 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) where messages that could not be processed by a container will be redirected. 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 rights to invoke the container 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](../../iam/operations/sa/create.md).

* [Registry](../../iot-core/concepts/index.md#registry) or [device](../../iot-core/concepts/index.md#device) from whose topics the trigger will receive message copies. If you have neither:

    * [Create a registry](../../iot-core/operations/registry/registry-create.md).
    * [Create a device](../../iot-core/operations/device/device-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 (device)`.
        * In the **Launched resource** field, select `Container`.

    1. Under **IoT Core message settings**, specify the registry, device, and MQTT topic to create a trigger for. When creating a trigger for a registry topic, you do not need to specify a device or an MQTT topic. If no MQTT topic is set, the trigger will fire for all registry or device 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 for a period of time not exceeding the specified timeout and sends them to a 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) to invoke it under.

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

        * In the **Interval** field, specify the time interval to retry invoking the container 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 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 internet-of-things \
      --name <trigger_name> \
      --registry-id <registry_ID> \
      --device-id <device_ID> \
      --mqtt-topic '<broker_MQTT_topic>' \
      --batch-size <message_batch_size> \
      --batch-cutoff <maximum_timeout> \
      --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.
    * `--registry-id`: [Registry ID](../../iot-core/operations/registry/registry-list.md).
    * `--device-id`: [Device ID](../../iot-core/operations/device/device-list.md). If you are creating a trigger for a registry topic, you can skip this setting.
    * `--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 registry or device 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 parameter. The values may range from 1 to 5. The default value is 1.
    * `--retry-interval`: Time to retry invoking the container 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 to the dead-letter queue. This is an optional parameter.

    Result:

    ```text
    id: a1s5msktijh2********
    folder_id: b1gmit33hgh2********
    created_at: "2022-10-24T15:19:15.353909857Z"
    name: iot-trigger
    rule:
      iot_message:
        registry_id: arenou2oj4h2********
        device_id: areqjd6un3h2********
        mqtt_topic: $devices/areqjd6unh2********/events
        batch_settings:
          size: "1"
          cutoff: 0s
        invoke_container:
          container_id: bba5jb38o8h2********
          service_account_id: aje3932acdh2********
          retry_settings:
            retry_attempts: "1"
            interval: 10s
    status: ACTIVE
    ```

- Terraform {#tf}

  With [Terraform](https://www.terraform.io/), you can quickly create a cloud infrastructure in Yandex Cloud and manage it using configuration files. These files store the infrastructure description written in HashiCorp Configuration Language (HCL). If you change the configuration files, Terraform automatically detects which part of your configuration is already deployed, and what should be added or removed.
  
  Terraform is distributed under the [Business Source License](https://github.com/hashicorp/terraform/blob/main/LICENSE). The [Yandex Cloud provider for Terraform](https://github.com/yandex-cloud/terraform-provider-yandex) is distributed under the [MPL-2.0](https://www.mozilla.org/en-US/MPL/2.0/) license.
  
  For more information about the provider resources, see the relevant documentation on the [Terraform](https://www.terraform.io/docs/providers/yandex/index.html) website or [its mirror](../../terraform/index.md).

  If you do not have Terraform yet, [install it and configure the Yandex Cloud provider](../../tutorials/infrastructure-management/terraform-quickstart.md#install-terraform).
  
  
  To manage infrastructure using Terraform under a service account or user accounts (a Yandex account, a federated account, or a local user), [authenticate](../../terraform/authentication.md) using the appropriate method.

  To create a trigger for Yandex IoT Core:

  1. Describe the trigger in the configuration file:

      ```hcl
      resource "yandex_function_trigger" "my_trigger" {
        name = "<trigger_name>"
        container {
          id                 = "<container_ID>"
          service_account_id = "<service_account_ID>"
          retry_attempts     = "<number_of_retry_attempts>"
          retry_interval     = "<time_between_retry_attempts>"
        }
        iot {
          registry_id  = "<registry_ID>"
          device_id    = "<device_ID>"
          topic        = "<broker_MQTT_topic>"
          batch_cutoff = "<maximum_wait_time>"
          batch_size   = "<message_batch_size>"
        }
        dlq {
         queue_id           = "<dead-letter_queue_ID>"
         service_account_id = "<service_account_ID>"
       }
      }
      ```

      Where:

      * `name`: Trigger name. Follow these naming requirements:

        * Length: between 3 and 63 characters.
        * It can only contain lowercase Latin letters, numbers, and hyphens.
        * It must start with a letter and cannot end with a hyphen.

      * `container`: Container settings:

        * `id`: Container ID.
        * `service_account_id`: ID of the service account with rights 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 parameter. The values may range from 1 to 5. The default value is 1.
        * `retry_intervall`: Time to retry invoking the container 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.

      * `iot`: Trigger settings:

        * `registry-id`: [Registry ID](../../iot-core/operations/registry/registry-list.md).
        * `device-id`: [Device ID](../../iot-core/operations/device/device-list.md). If you are creating a trigger for a registry topic, you can skip this setting.
        * `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 registry or device topics.
        * `batch_cutoff`: Maximum wait time. This is an optional setting. The values may range from 1 to 60 seconds. The default value is 1 second. The trigger groups messages within the `batch_cutoff` period and sends them to the container. The number of messages cannot exceed `batch_size`.
        * `batch_size`: Size of the message batch from MQTT topics. This is an optional setting. The values may range from 1 to 10. The default value is 1.

      * `dlq`: Dead-letter queue settings:
          * `queue_id`: Dead-letter queue ID.
          * `service_account_id`: ID of the service account with write permissions for the dead-letter queue.

      For more information about resource properties in Terraform, see [this provider guide](../../terraform/resources/function_trigger.md).

  1. Create the resources:

      1. In the terminal, navigate to the configuration file directory.
      1. Make sure the configuration is correct using this command:
      
         ```bash
         terraform validate
         ```
      
         If the configuration is valid, you will get this message:
      
         ```bash
         Success! The configuration is valid.
         ```
      
      1. Run this command:
      
         ```bash
         terraform plan
         ```
      
         You will see a list of resources and their properties. No changes will be made at this step. Terraform will show any errors in the configuration.
      1. Apply the configuration changes:
      
         ```bash
         terraform apply
         ```
      
      1. Type `yes` and press **Enter** to confirm the changes.

      Terraform will create all the required resources. You can check the new resources using the [management console](https://console.yandex.cloud) or this [CLI](../../cli/quickstart.md) command:

      ```bash
      yc serverless trigger list
      ```

- 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}

Make sure the trigger is working properly. To do this, view [container logs](../concepts/logs.md) that show information about invocations.

## See also {#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 registry or device topic](../../api-gateway/operations/trigger/iot-core-trigger-create.md)