FCM: Retry-after and exponential backoff
问题 As I understand, when a message fails to be delivered, the Retry-After header is sometimes included in the response and sometimes not. But what happens if I first receives an error response with Retry-After included, resends the message and receives another error response but without Retry-After? I know I should use exponential backoff but how does that work when the previous waiting time was from the Retry-After header? Imagine this sequence of requests and responses: Request 1: No waiting