Contact UsGet started

Creating a timer that sends messages to WebSocket connections

Written by
Updated at May 5, 2025

Create a timer, i.e., a trigger to send messages to WebSocket connections on schedule.

Getting started

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.

    Note

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

  • Service account with the api-gateway.websocketBroadcaster role. If you do not have a service account, create one.

Creating a trigger

Note

The trigger is initiated within 5 minutes of being created.

  1. In the management console, select the folder where you want to create a trigger.

  2. Open API Gateway.

  3. In the left-hand panel, select Triggers.

  4. Click Create trigger.

  5. Under Basic settings:

    • Enter a name and description for the trigger.
    • In the Type field, select Timer.
    • In the Launched resource field, select API gateway.

  6. Under Timer settings:

    • In the Cron expression field, specify a schedule for sending messages to WebSocket connections as a cron expression.
    • Optionally, in the Payload field, specify the message that will be sent to WebSocket connections if the timer fires in the payload field. The data type is a string up to 4,096 characters long.

  7. 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 to send messages to WebSocket connections.

  8. Click Create trigger.

If you do not have the Yandex Cloud CLI yet, install and initialize it.

The folder specified when creating the CLI profile is used by default. To change the default folder, use the yc config set folder-id <folder_ID> command. You can specify a different folder using the --folder-name or --folder-id parameter.

To create a trigger that sends messages to WebSocket connections, run this command:

yc serverless trigger create timer \
  --name <timer_name> \
  --cron-expression '<cron_expression>' \
  --payload <message> \
  --gateway-id <API_gateway_ID> \
  --gateway-websocket-broadcast-path <path> \
  --gateway-websocket-broadcast-service-account-id <service_account_ID>

Where:

  • --name: Timer name.
  • --cron-expression: Schedule for sending messages to WebSocket connections as a cron expression.
  • --payload: Message that will be sent to WebSocket connections if the timer fires. The string length must not exceed 4,096 characters.
  • --gateway-id: API gateway ID.
  • --gateway-websocket-broadcast-path: Path in the OpenAPI specification. Messages will be sent through WebSocket connections established using this path.
  • --gateway-websocket-broadcast-account-id: Service account ID with permissions to send messages to WebSocket connections.

Result:

id: a1s5msktijh2********
folder_id: b1gmit33hgh2********
created_at: "2023-08-04T15:19:15.353909857Z"
name: timer
rule:
  timer:
    cron_expression: 5 10 ? * * *
    payload: <message>
    gateway_websocket_broadcast:
      gateway_id: d4eofc7n0mh2********
      path: /
      service_account_id: aje3932acdh2********
status: ACTIVE

To create a timer, use the create REST API method for the Trigger resource or the TriggerService/Create gRPC API call.

Checking the result

Check that the trigger operates correctly. Do it by viewing the API gateway logs that present information about its incoming requests.

See also

Previous
Getting information about a trigger
Next
Creating a trigger for Message Queue