Duplicate webhook handling
Duplicate webhooks are defined as two or more webhooks that meet the following conditions:
- on the same object
- created by the same user
- have identical:
callbackUrlandsubscopeproperties.
Because duplicate webhooks are functionally identical, this would ordinarily result in the callback URL being called simultaneously once for each duplicate webhook in the object when the object changes. Many duplicates can lead to too much traffic which can cause a denial of service (DOS) on the callback server.
There are no known valid use cases for duplicate webhooks; they are usually created unintentionally by API clients due to faulty or missing logic.
For this reason, as of January 2023, Smartsheet will now deduplicate webhook callbacks. This means for every set of duplicate webhooks on an object, Smartsheet will no longer issue one callback per webhook, and will instead only issue one total callback, for only the oldest enabled webhook.
Recommendation: When creating a webhook, first check to make sure that the object doesn't already contain an identical webhook. If it does, and it's disabled, re-enable it. If it's already enabled, do nothing.