Errors

An error answers with its status and a JSON body. _tag names the error, message explains it, and some errors add fields:

SpendEventConflict

{
  "_tag": "SpendEventConflict",
  "id": "se:acme:alice:clearing:txn_0001",
  "message": "This event ID was already used by an event with different content"
}

Status	`_tag`	Extra fields	Retry?
`400`	`InvalidRequest`	`part`: `Payload`, `Query`, `Params` or `Headers`	No: fix the request
`401`	`Unauthorized`		No: check your key
`403`	`IntegratorMismatch`		No
`403`	`IntegratorSuspended`		No: contact Gave
`409`	`SpendEventConflict`	`id`	No: the ID was used with different content
`409`	`SimulationConflict`	`reference`	No: use a new reference
`422`	`EventInFuture`		No: check the sender's clock
`422`	`SimulationRefused`	`reference`	No
`429`	`RateLimited`	`retryAfterSeconds`	Yes, after that delay
`503`	`Unavailable`		Yes, with backoff

Retrying

Retry 429, 503, timeouts and network errors with the same request. Every write is idempotent, so a request that did go through the first time is answered as a duplicate, and changes nothing. Wait longer between each attempt, with some randomness, and give up after a bound you choose.

Never retry any other 4xx unchanged: it will be refused again.