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

# Creating a timer that invokes a container from Serverless Containers

Create a [timer](../concepts/trigger/timer.md), i.e., a trigger that invokes a [container](../concepts/container.md) in Serverless Containers on a schedule.

## Getting started {#before-you-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).

## 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 `Timer`.
        * In the **Launched resource** field, select `Container`.

    1. Under **Timer settings**:

        * In the **Cron expression** field, specify the function invocation schedule as a [cron expression](../concepts/trigger/timer.md#cron-expression).
        * Optionally, in the **Payload** field, enter a message to send to the function as `payload` when the timer fires. The data type is a string up to 4,096 characters long.

    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 timer \
      --name <timer_name> \
      --cron-expression '<cron_expression>' \
      --payload <message> \
      --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`: Timer name.
    * `--cron-expression`: Container invocation schedule specified as a [cron expression](../concepts/trigger/timer.md#cron-expression).
    * `--payload`: Message to send to the function when the timer fires. The string length must not exceed 4,096 characters.

    * `--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: timer
    rule:
      timer:
        cron_expression: 5 10 ? * * *
        payload: <message>
        invoke_container_with_retry:
          container_id: bba5jb38o8h2********
          service_account_id: aje3932acdh2********
          retry_settings:
            retry_attempts: "1"
            interval: 10s
          dead_letter_queue:
            queue-id: yrn:yc:ymq:ru-central1:b1gmit33ngh2********:dlq
            service-account-id: aje3932acdh2********
    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 guides 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 timer:

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

      ```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>
        }
        timer {
          cron_expression = "<cron_expression>"
          payload         = "<message>"
        }
        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 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.

      * `timer`: Trigger settings:

          * `cron_expression`: Container invocation schedule specified as a [cron expression](../concepts/trigger/timer.md#cron-expression).
          * `payload`: Message to send to the container when the timer fires. The string length must not exceed 4,096 characters.

      * `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 on the properties of the `function_trigger` resource, 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 timer, 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 timer that invokes Cloud Functions](../../functions/operations/trigger/timer-create.md)
* [Creating a timer that sends messages to WebSocket connections](../../api-gateway/operations/trigger/timer-create.md)