# Creating a trigger for a registry or device topic

{% note warning %}

Yandex IoT Core is no longer available to new users. 

Current users can create resources until November 1, 2026. Afterwards, the service will go read-only and cease to operate on December 1, 2026. For more information on the timing and procedure, see [Service shutdown](../sunset.md).

{% endnote %}

Create a [trigger](../../functions/concepts/trigger/iot-core-trigger.md) for a [Yandex IoT Core](../index.md) [device](../concepts/index.md#device) or [registry](../concepts/index.md#registry) [topic](../concepts/topic/index.md) and process message copies using a [function](../../functions/concepts/function.md) from [Yandex Cloud Functions](../../functions/index.md).

{% note warning %}

The trigger must be in the same [cloud](../../resource-manager/concepts/resources-hierarchy.md#cloud) as the registry or device whose topic it reads messages from.

{% endnote %}

## Getting started {#before-you-begin}

To create a trigger, you will need:

* Function the trigger will invoke. If you do not have a function:

    * [Create a function](../../functions/operations/function/function-create.md).
    * [Create a function version](../../functions/operations/function/version-manage.md).

* Optionally, a [dead-letter queue](../../functions/concepts/dlq.md) where to redirect the messages the function failed to process. If you do not have a queue, [create one](../../message-queue/operations/message-queue-new-queue.md).

* [Service accounts](../../iam/concepts/users/service-accounts.md) with permissions to invoke the function 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).

* Registry or device whose topics the trigger will receive message copies from. If you have neither:
  * [Create a registry](registry/registry-create.md).
  * [Create a device](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](../../resource-manager/concepts/resources-hierarchy.md#folder) where you want to create a trigger.
  
  1. Navigate to **Cloud Functions**.
  
  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 `Function`.
  
  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 within the specified wait time period and sends them to the function. The number of messages cannot exceed the specified batch size.
  
  1. Under **Function settings**, select a function and specify:

     * [Function version tag](../../functions/concepts/function.md#tag).
     * [Service account](../../iam/concepts/users/service-accounts.md) to use for invoking the function.

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

     * In the **Interval** field, specify how long to wait before retrying the function 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 function 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.

  1. Optionally, under **Dead Letter Queue settings**, select a dead-letter queue and a [service account](../../iam/concepts/users/service-accounts.md) 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 function, run this command:

  ```bash
  yc serverless trigger create internet-of-things \
    --name <trigger_name> \
    --registry-id <registry_ID> \
    --device-id <device_ID> \
    --mqtt-topic '<MQTT_topic>' \
    --batch-size <message_batch_size> \
    --batch-cutoff <maximum_wait_time> \
    --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.
  * `--registry-id`: [Registry ID](registry/registry-list.md).
  * `--device-id`: [Device ID](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 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 invoke the function.
  * `--retry-attempts`: Number of invocation retries before the trigger sends 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 function 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: a1sl0mkmimfj********
  folder_id: b1g88tflru0e********
  created_at: "2019-09-25T13:54:35.654935Z"
  name: iot-trigger
  rule:
    iot_message:
      registry_id: arenou2oj4ct********
      device_id: areqjd6un3af********
      mqtt_topic: $devices/areqjd6un3af********/events
      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
  ```

- 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. In the Terraform configuration file, describe the resources you want to create:

     ```
     resource "yandex_function_trigger" "my_trigger" {
       name        = "<trigger_name>"
       description = "<trigger_description>"
       function {
         id                 = "<function_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        = "<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.
     
     * `description`: Trigger description.
     
     * `function`: Function settings:
     
         * `id`: Function ID.
         * `service_account_id`: ID of the service account with permissions to invoke the function.
         * `retry_attempts`: Number of invocation retries before the trigger sends 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 function if it fails. This is an optional setting. The values may range from 10 to 60 seconds. The default value is 10 seconds.

     * `iot`: Trigger settings:

        * `registry-id`: [Registry ID](registry/registry-list.md).
        * `device-id`: [Device ID](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 for a period not exceeding `batch-cutoff` and sends them to a function. 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 `yandex_function_trigger` properties, 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](../../functions/triggers/api-ref/Trigger/create.md) REST API method for the [Trigger](../../functions/triggers/api-ref/Trigger/index.md) resource or the [TriggerService/Create](../../functions/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 [function logs](../../functions/operations/function/function-logs.md) that show information on invocations.

## See also {#see-also}

* [Creating a trigger that will send messages to a container in Serverless Containers from a Yandex IoT Core registry or device topic](../../serverless-containers/operations/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)