[Yandex Cloud documentation](../../../index.md) > [Yandex API Gateway](../../index.md) > [Step-by-step guides](../index.md) > Creating a trigger > Creating a Telegram trigger

# How to create a Telegram trigger that sends messages to WebSocket connections

Create a [Telegram trigger](../../concepts/trigger/telegram-trigger.md) that sends messages to Yandex API Gateway [WebSocket connections](../../concepts/extensions/websocket.md) when your Telegram bot receives an update.

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

To create a trigger, you will need:

* API gateway. Messages will be sent to WebSocket connections accessing the API gateway at the path specified in the trigger settings. If you do not have an API gateway, [create one](../api-gw-create.md).

    {% note info %}

    The trigger does not call the API gateway when sending messages to WebSocket connections.

    {% endnote %}

* [Service account](../../../iam/concepts/users/service-accounts.md) with the `api-gateway.websocketBroadcaster` role. If you do not have a service account, [create one](../../../iam/operations/sa/create.md).

* Telegram bot and its token. If you do not have a bot, create one using [@BotFather](https://core.telegram.org/bots/features#botfather) and copy the issued token.

## 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 your trigger.

    1. [Navigate](https://console.yandex.cloud/link/api-gateway) to **API Gateway**.

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

    1. Click **Create trigger**.

    1. Under **Basic settings**:

        * Optionally, enter a trigger name and description.

        * In the **Labels** field, click **Add label** and specify the labels in `key: value` format.

        * In the **Type** field, select `Telegram`.

    1. Under **Telegram settings**, specify the Telegram bot token you received from [@BotFather](https://core.telegram.org/bots/features#botfather).

    1. Under **Batch message settings**, specify the following:
       
       * **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 1,000. The default value is 1.
       
       The trigger groups events within the specified wait time and sends them to the target. The number of events cannot exceed the specified batch size.

    1. Under **Targets**:

        1. In the **Target type** field, select `API gateway`.

        1. Under **API gateway settings**:
           * In the **API gateway** field, select the API gateway.
           * In the **Path** field, specify the path in the OpenAPI specification. Messages will be sent through WebSocket connections established using this path.
           * In the **Service account** field, select the [service account](../../../iam/concepts/users/service-accounts.md) to send messages to WebSocket connections.

        1. Optionally, in the **Filter** field, specify a jq template to filter events sent to the target. If no filter is specified, all events are sent to the target.

        1. Optionally, in the **Transformation template** field, specify a `jq` template to transform events before sending them to the target. If no template is specified, no transformations apply to the events.

    1. Click **Create trigger**.

- 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 Telegram that sends messages to WebSocket connections:

    1. Describe the trigger in the configuration file:

       ```hcl
       resource "yandex_serverless_triggers" "my_trigger" {
         name = "<trigger_name>"
         source {
           telegram_message {
             bot_token       = "<Telegram_bot_token>"
             allowed_updates = [ "<update_type>", "<update_type>" ]
             force           = true
           }
         }
         action {
           gateway_websocket_broadcast {
             gateway_id         = "<API_gateway_ID>"
             path               = "<WebSocket_connection_path>"
             service_account_id = "<service_account_ID>"
           }
           filter {
             jq = ".message.text | startswith(\"/\")"
           }
           transformer {
             jq = ".message"
           }
           retry_policy {
             retry_attempts = "<number_of_retries>"
             interval       = "<interval_between_retries>"
           }
           dead_letter {
             dead_letter_queue {
               queue_arn          = "<Dead_Letter_Queue_ARN>"
               service_account_id = "<service_account_ID>"
             }
           }
         }
       }
       ```

       Where:

       * `name`: Trigger name. The name format is as follows:
       
           * 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. This is an optional parameter.
       * `labels`: Trigger labels in `key:value` format. This is an optional parameter.

       * `source`: Event source settings:

         * `telegram_message`: Telegram bot settings:

           * `bot_token`: Telegram bot token received from [@BotFather](https://core.telegram.org/bots/features#botfather). The value is only provided when creating or updating a trigger. Terraform does not return the value in its output. When the token changes, the webhook is re-registered.
           * `allowed_updates`: List of [Telegram update](https://core.telegram.org/bots/api#update) types the bot subscribes to. This is an optional setting. The default value is `[ "message" ]`.
           * `force`: Reinstalling the webhook if the bot already has a webhook configured for another URL. Without this setting, creating a trigger will fail with an error. If the webhook already points to the trigger, this setting has no effect. This is an optional parameter.

       * `action`: Target settings. You can specify this section multiple times so the trigger calls multiple resources, including those of different types. There are [limits](../../concepts/limits.md#api-gw-limits) on the maximum number of resources.
       
           * `gateway_websocket_broadcast`: API gateway settings:
       
               * `gateway_id`: API gateway ID.
               * `path`: Path in the OpenAPI specification. Events will be sent through WebSocket connections established using this path.
               * `service_account_id`: ID of the service account with permissions to send events to WebSocket connections.
           
           * `filter`: Filtering events before sending them to the target. This is an optional section.
           
               * `jq`: [jq template](https://jqlang.github.io/jq/manual/) to filter events sent to the target. It not specified, all events reach the target.
           
           * `transformer`: Transforming events before sending them to the target. This is an optional section.
           
               * `jq`: jq template to transform events before sending them to the target. It omitted, no transformations apply to the events.
           
           * `retry_policy`: Repeated request settings. This is an optional section.
           
               * `interval`: Time interval before a retry attempt to send the event if the current attempt fails.
               * `retry_attempts`: Number of retry attempts before the trigger moves the event to the dead-letter queue.
           
           * `dead_letter`: Dead-letter queue settings. This is an optional section.
           
               * `dead_letter_queue`: Queue settings:
           
                   * `queue_arn`: Queue ARN.
                   * `service_account_id`: ID of the service account with permissions to write to the queue.
                   * `message_attributes`: Attributes to add to each message in the queue, in `key:value` format. This is an optional parameter.

       For more on the properties of the `yandex_serverless_triggers` resource, see [this provider guide](../../../terraform/resources/serverless_triggers.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
        ```

{% endlist %}

## Checking the result {#check-result}

Check that the trigger operates correctly. Do it by viewing the [API gateway logs](../api-gw-logs.md) that present information about its incoming requests.

#### Useful links {#see-also}

* [Telegram Trigger that invokes a function from Cloud Functions](../../../functions/operations/trigger/telegram-trigger-create.md)
* [Telegram Trigger that invokes a container from Serverless Containers](../../../serverless-containers/operations/telegram-trigger-create.md)