Creating a one-off scheduled event

Introduction

One-off scheduled events are used to reliably trigger an HTTP webhook to run custom business logic at a particular point in time. For example, you can create a scheduled event to send a reminder email two weeks after a user signs up.

To add a one-off scheduled event, follow these steps:

Step 1: Define the scheduled event

The following fields for required to define a scheduled event:

• Webhook: The HTTP endpoint that should be triggered.
• Time: The time to trigger the event.
• Payload: The JSON payload which will be sent to the webhook.

Console

Navigate to Events > One-off Scheduled Events > Schedule an event in your Hasura console.

In the form opened by the above step, fill out the fields defined above:

CLI

One-off scheduled events cannot be set using the CLI as they are not tracked as a part of Hasura metadata.

API

You can define a scheduled event via the create_scheduled_event metadata API:

POST /v1/metadata HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
   "type": "create_scheduled_event",
   "args": {
      "webhook": "https://send-email.com",
      "schedule_at": "2022-06-18T18:45:00Z",
      "payload": { "email": "bob@ross.com" }
   }
}

Step 2: Define advanced options (Optional)

If you like, you can also define advanced values:

• Headers: List of headers to be sent to the webhook.
• Retry configuration: In case the call to the webhook fails.
• Comment: Custom description of the scheduled trigger.

Console

Expand the Advanced section.

CLI

One-off scheduled events cannot be set using the CLI as they are not tracked as a part of Hasura metadata.

API

You can define advanced options when defining a scheduled event via the create_scheduled_event metadata API:

POST /v1/metadata HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
   "type": "create_scheduled_event",
   "args": {
      "webhook": "https://send-email.com",
      "schedule_at": "2022-06-18T18:45:00Z",
      "payload": {
            "email": "bob@ross.com"
      },
      "headers": [
            {
               "name": "key",
               "value": "value"
            }
      ],
      "retry_conf": {
            "num_retries": 3,
            "timeout_seconds": 120,
            "tolerance_seconds": 21675,
            "retry_interval_seconds": 12
      },
      "comment": "sample scheduled event comment"
   }
}

Schedule & logs

Once you've created your scheduled trigger, you can see Pending events, Processed events, and Invocation logs in their respective tabs.

Note

A scheduled event will be delivered within ten seconds of when it's scheduled. For example, if you schedule an event at 09:24:10, it will be delivered between 09:24:10 and 09:24:20.

This is because Hasura currently checks for events to be delivered at 10 second intervals. This interval will be made configurable soon.