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

# Creating a trigger for Message Queue that sends messages to a container in Serverless Containers

Create a [trigger for a Message Queue](../concepts/trigger/ymq-trigger.md) and process messages using a [container](../concepts/container.md) in Serverless Containers.

{% note warning %}

* You can only create a trigger for a standard message queue.
* The trigger must be in the same cloud as the queue from which it reads messages.
* You can create only one trigger for each message queue.

{% endnote %}

## Getting started {#before-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).

* [Service accounts](../../iam/concepts/users/service-accounts.md) with the following permissions:

    * To invoke a container.
    * To read from the queue the trigger receives messages from.

    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).

* Message queue the trigger will receive messages from. If you do not have a queue, [create one](../../message-queue/operations/message-queue-new-queue.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 `Message Queue`.
        * In the **Launched resource** field, select `Container`.

    1. Under **Message Queue message settings**, select a message queue and a service account with the permission to read messages from that queue.

    1. Under **Batch message settings**, specify:

        * **Waiting time, s**. The values may range from 0 to 20 seconds. The default value is 10 seconds.
        * **Batch size**. The values may range from 1 to 1,000. The default value is 1.

        The trigger groups messages within the specified wait time period and sends them to the 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) that will invoke it.

    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 message-queue \
      --name <trigger_name> \
      --queue <queue_ID> \
      --queue-service-account-id <service_account_ID> \
      --invoke-container-id <container_ID> \
      --invoke-container-service-account-id <service_account_ID> \
      --batch-size <message_batch_size> \
      --batch-cutoff <maximum_wait_time>
    ```

    Where:

    * `--name`: Trigger name.
    * `--queue`: Queue ID.

        To find out the queue ID:
        
        1. In the [management console](https://console.yandex.cloud), navigate to the folder containing the queue.
        1. Select **Message Queue**.
        1. Select the queue.
        1. You can see the queue ID under **General information** in the **ARN** field.

    * `--invoke-container-id`: Container ID.
    * `--queue-service-account-id`: ID of the service account with permissions to read messages from the queue.
    * `--invoke-container-service-account-id`: ID of the service account with permissions to invoke the container.
    * `--batch-size`: Message batch size. This is an optional setting. The values may range from 1 to 1,000. The default value is 1.
    * `--batch-cutoff`: Maximum wait time. This is an optional setting. The values may range from 0 to 20 seconds. The default value is 10 seconds. The trigger groups messages within the `batch-cutoff` period and sends them to the container. The number of messages cannot exceed `batch-size`.

    Result:

    ```text
    id: a1s5msktijh2********
    folder_id: b1gmit33hgh2********
    created_at: "2022-10-24T15:19:15.353909857Z"
    name: ymq-trigger
    rule:
      message_queue:
        queue_id: yrn:yc:ymq:ru-central1:b1gmit33ngh2********:my-mq
        service_account_id: bfbqqeo6jkh2********
        batch_settings:
          size: "1"
          cutoff: 10s
        invoke_container:
          container_id: bba5jb38o8h2********
          service_account_id: bfbqqeo6jkh2********
    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 Message Queue:

  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>"
       }
       message_queue {
         queue_id           = "<queue_ID>"
         service_account_id = "<service_account_ID>"
         batch_cutoff       = "<maximum_wait_time>"
         batch_size         = "<message_batch_size>"
       }
     }
     ```

     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.

     * `message_queue`: Trigger settings:

         * `queue_id`: Queue ID.

             To find out the queue ID:
             
             1. In the [management console](https://console.yandex.cloud), navigate to the folder containing the queue.
             1. Select **Message Queue**.
             1. Select the queue.
             1. You can see the queue ID under **General information** in the **ARN** field.

         * `service_account_id`: ID of the service account with permissions to read messages from the queue.

         * `batch_cutoff`: Maximum wait time. This is an optional setting. The values may range from 0 to 20 seconds. The default value is 10 seconds. 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`: Message batch size. This is an optional setting. The values may range from 1 to 1,000. The default value is 1.

     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 Message Queue, 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}

{% list tabs %}

- Serverless Containers

    Check that the trigger works correctly. To do this, view [container logs](../concepts/logs.md) that show information on invocations.

- Message Queue

    Check that the number of enqueued messages is decreasing. To do this, view the queue statistics:

   1. In the [management console](https://console.yandex.cloud), go to the folder where you created the trigger.
   1. Navigate to **Message Queue**.
   1. Select the queue for which you created the trigger.
   1. Go to **Monitoring**. Check the **Messages in the queue** chart.

{% endlist %}


## Useful links {#see-also}

* [Creating a trigger for Message Queue that sends messages to Cloud Functions](../../functions/operations/trigger/ymq-trigger-create.md)
* [Creating a trigger for Message Queue that sends messages to WebSocket connections](../../api-gateway/operations/trigger/ymq-trigger-create.md)