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What is an idempotency key?

Primer supports a request idempotency mechanism for our Payments API. This optional feature enables you to safely retry a request without risking the user being charged or refunded multiple times. This is particularly useful when an API call fails due to the request being invalid, due to a network issue, or if Primer is momentarily unavailable. If this is the case, make another request with the same idempotency key:
  • If a request with the same idempotency key has already been successfully processed by Primer, the new request will be ignored. A 409 error will be returned with an errorId set to IdempotencyKeyAlreadyExists.
  • Otherwise, Primer will attempt to process the new request.

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How to use an idempotency key

To make an idempotent request, generate an idempotency key and pass it to the header X-Idempotency-Key. 
curl -X POST 'https://api.primer.io/<ENDPOINT>' \
  --header 'X-Idempotency-Key: <idempotency-key>'
The way you generate the key is totally up to you, as long as it is unique per request attempt. Keep in mind that a payment request resulting in a declined or failed payment is still considered Successfully processed for the API. Therefore, if you want to allow the user to retry an unsuccessful payment, make sure to not use the same idempotency key. As a such, don’t use anything too restrictive like an orderId for the idempotency key as multiple payment attempts and refunds can be made for a single order.