[Yandex Cloud documentation](../../../index.md) > [Yandex Cloud Functions](../../index.md) > [Step-by-step guides](../index.md) > Creating a trigger > Creating a trigger for Cloud Logging

# Creating a trigger for Cloud Logging that invokes Cloud Functions

Create a [trigger for Cloud Logging](../../concepts/trigger/cloud-logging-trigger.md) that invokes [Cloud Functions](../../concepts/function.md) whenever entries are added to the [log group](../../../logging/concepts/log-group.md).

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

* Optionally, a [dead-letter queue](../../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).

* Log group whose new entries will set off the trigger. If you do not have a log group, [create one](../../../logging/operations/create-group.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 **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 `Cloud Logging`.
        * In the **Launched resource** field, select `Function`.

    1. Under **Cloud Logging settings**, specify:

        * Log group.
        * Optionally, types of resources, e.g., `serverless.function` in Cloud Functions.
        * Optionally, IDs of your resources or Yandex Cloud resources, e.g., functions in Cloud Functions.
        * Optionally, log streams.
        * Optionally, logging levels.
        
        A trigger fires when the specified log group receives entries that comply with all of the optional settings. If the optional setting is not specified, the trigger fires for any value.

    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](../../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 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 logging \
      --name <trigger_name> \
      --log-group-name <log_group_name> \
      --batch-size <message_batch_size> \
      --batch-cutoff <maximum_wait_time> \
      --resource-ids <resource_ID> \
      --resource-types <resource_type> \
      --stream-names <log_stream> \
      --log-levels <logging_level> \
      --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.
    * `--log-group-name`: Name of the log group whose new log entries will invoke the function.

    * `--batch-size`: Message batch size. This is an optional setting. The values may range from 1 to 10. The default value is 1.
    * `--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 function. The number of messages cannot exceed `batch-size`.

    * `--resource-ids`: IDs of your resources or Yandex Cloud resources, e.g., functions in Cloud Functions. This is an optional setting.
    * `--resource-types`: Types of resources, e.g., `serverless.function` in Cloud Functions. This is an optional setting.
    * `--stream-names`: Log streams. This is an optional setting.
    * `--log-levels`: Logging levels. This is an optional setting.
      A trigger fires when the specified log group receives entries that comply with all of the following settings: `resource-ids`, `resource-types`, `stream-names`, and `log-levels`. If the setting is not specified, the trigger fires for any value.

    * `--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: a1sfe084v4**********
    folder_id: b1g88tflru**********
    created_at: "2019-12-04T08:45:31.131391Z"
    name: logging-trigger
    rule:
      logging:
        log-group-name: default
        resource_type:
          - serverless.functions
        resource_id:
          - d4e1gpsgam78********
        stream_name:
          - test
        levels:
          - INFO
        batch_settings:
          size: "1"
          cutoff: 1s
        invoke_function:
          function_id: d4eofc7n0m**********
          function_tag: $latest
          service_account_id: aje3932acd**********
          retry_settings:
            retry_attempts: "1"
            interval: 10s
          dead_letter_queue:
            queue-id: yrn:yc:ymq:ru-central1:aoek49ghmk**********:dlq
            service-account-id: aje3932a**********
    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 trigger for Cloud Logging:

  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>"
       }
       logging {
          group_id       = "<log_group_ID>"
          resource_types = [ "<resource_type>" ]
          resource_ids   = [ "<resource_ID>" ]
          stream_names   = [ "<log_stream>" ]
          levels         = [ "<logging_level>", "<logging_level>" ]
          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.

     * `logging`: Trigger settings:

        * `group_id`: ID of the log group whose new log entries will invoke the function.
        * `resource_types`: Types of resources, e.g., Cloud Functions such as `resource_types = [ "serverless.function" ]`. You can specify multiple types. 
        * `resource_ids`: IDs of your resources or Yandex Cloud resources, e.g., `resource_ids = [ "<function_ID>" ]`. You can specify multiple IDs.
        * `stream_names`: Log streams. This is an optional setting.
        * `levels`: Logging levels, e.g., `levels = [ "INFO", "ERROR"]`.

          A trigger fires when the specified log group receives entries that comply with all of the following settings: `resource-ids`, `resource-types`, `stream-names`, and `levels`. If the setting is not specified, the trigger fires for any value.

        * `batch_cutoff`: Maximum wait time. The valid values range from 0 to 60 seconds. 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`.
        * `batch_size`: Message batch size. The valid values range from 1 to 10.

     * `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 `yandex_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 trigger for Cloud Logging, 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 [function logs](../function/function-logs.md) that show information on invocations.

## Useful links {#see-also}

* [Creating a trigger for Cloud Logging that invokes a container from Serverless Containers](../../../serverless-containers/operations/cloud-logging-trigger-create.md)
* [Creating a trigger for Cloud Logging that sends messages to WebSocket connections](../../../api-gateway/operations/trigger/cloud-logging-trigger-create.md)