429 status code

[nickevansuk]

The specification currently does not recognise 429, which is common in real-world implementations.

Propose the following is added:

HTTP Status Code	Interpretation	Expected consumer (System 2) behaviour
429	Too Many Requests / Rate Limiting	Retry after a random interval between 5 and 15 minutes, to ease load from multiple consumers

[nathansalter]

@nickevansuk Do you think it's worth allowing/requiring providers to supply the Retry-After header so that they can decide how much to push back, allowing them to do things such as prioritisation or exponential back-off?

[nickevansuk]

Great idea @nathansalter! Gladstone already implements this in fact.

So we could amend the above proposal to: "Retry after the interval specified by the Retry-After header, or if not specified after a random interval between 5 and 15 minutes, to ease load from multiple consumers"

Or similar?