Creating an event trigger

Table of contents

Event triggers can be created using the Hasura console or metadata APIs.

Open the Hasura console, head to the Events tab and click on the Create button to open the page below:

Parameters

Trigger Name

Unique name for event trigger.

Schema/Table

The postgres schema and table name on which the event trigger needs to be created.

Trigger Operations

The table operation on which the event trigger will be invoked.

Webhook URL

The HTTP(s) URL which will be called with the event payload on configured operation. Must be a POST handler. This URL can be entered manually or can be picked up from an environment variable (the environment variable needs to be set before using it for this configuration).

Advanced Settings

Listen columns for update

Update operations are special because you may want to trigger a webhook only if specific columns have changed in a row. Choose the columns here which you want the update operation to listen to.

If a column is not selected here, then an update to that column will not trigger the webhook.

Retry Logic

Retry configuration is available in the “Advanced settings” when you create a trigger.

  1. num_retries: Number of times a failed invocation is retried. Default value is 0.
  2. interval_sec: Number of seconds after which a failed invocation is retried. Default value is 10.
  3. timeout_sec:: Number of seconds before which client closes the connection to the webhook. Default value is 60.

Headers

Custom headers can be added to an event trigger. Each webhook request will have these headers added.

Each header has 3 parameters:

  1. Key: Name of the header e.g. Authorization or X-My-Header.
  2. Type: One of static or from env variable. static means the value provided in the Value field is the raw value of the header. from env variable means the value provided in the Value field is the name of the environment variable in the GraphQL engine which will be resolved before sending the header.
  3. Value: The value of the header. Either a static value or the name of an environment variable.