Timer that sends messages to WebSocket connections

A timer is a trigger that sends messages to WebSocket connections on schedule. The schedule is entered as a cron expression. The cron expression uses UTC+0.

A timer requires a service account to send messages to WebSocket connections.

For more information about creating a timer, see Creating a timer that sends messages to WebSocket connections.

Cron expression formatCron expression format

The order of fields in the cron expression: Minutes Hours Day-of-month Month Day-of-week Year.

Possible field valuesPossible field values

Special charactersSpecial characters

You can use the following special characters in cron expressions:

• *: Select all values in the field.

  The * character in the Minutes field: The trigger starts every minute.

• ?: Select any field value. You can't fill Day of month and Day of week at the same time. If you entered a value in one of these fields, enter ? in the other field.

  10 in Day of month and ? in Day of week: The trigger is launched every 10th day of the month.

• -: Select a range of values.

  The 10-12 range in Hours: the trigger runs at 10 AM, 11 AM, and noon.

• ,: Select multiple values.

  MON,WED,FRI in the Day of week field: the trigger runs on Monday, Wednesday, and Friday.

• /: Increment the value.

  0/15 in the Minutes field: The trigger starts at 0, 15, 30, and 45 minutes past each hour.

• L: This character functions differently in the two fields where it's used:

  • In the Day of month field, it means the last day of the month.
  • In the Day of week field, it means the last day of the week, 7 (Saturday, SAT).

  L in the Day of month field: the trigger runs on January 31, February 28, and so on.

• W: Select the weekday nearest to the specified date.

  15W in the Day of month field: The trigger is run on the weekday nearest to the 15th day of the month. If the 15th day is Saturday, the trigger runs on Friday the 14th.

  Note

  The characters L and W in the Day of month field can be also merged into LW: The trigger is run on the last weekday of the month.

• #: Select the Nth day of the month.

  The value 6#3 in the Day of week field: The trigger runs on the third Friday of the month (6 — Friday, 3 — the third Friday of the month).

Examples of cron expressionsExamples of cron expressions

Roles required for timers to run correctlyRoles required for timers to run correctly

• To create a timer, you need a permission for the service account under which the timer executes the operation. This permission comes with the iam.serviceAccounts.user and editor roles or higher.
• To activate a timer, the service account needs the api-gateway.websocketBroadcaster role for the folder containing the API gateway.

Read more about access management.

Timer message formatTimer message format

After the trigger fires, it will send the following message to WebSocket connections:

{
  "messages": [
    {
      "event_metadata": {
        "event_id": "a1s41g2n5g0o********",
        "event_type": "yandex.cloud.events.serverless.triggers.TimerMessage",
        "created_at": "2019-12-04T12:05:14.227761Z",
        "cloud_id": "b1gvlrnlei4l********",
        "folder_id": "b1g88tflru0e********"
      },
      "details": {
        "trigger_id": "a1sfe084v4se********",
        "payload": "payload-message"
      }
    }
  ]
}

See alsoSee also

• Timer to run a Serverless Containers container
• Timer to run a Cloud Functions function