package reddit_api_async

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Retry_manager handles transient errors due to blips in networking or Reddit's infrastructure.

When a request is sent via a retry manager, a transient error causes the manager to periodically query the Reddit API to detect a resumption of ordinary service. After this query succeeds, the original request is retried.

As a result, the return type of does not include transient errors.

Warning. Do not use Retry_manager if it is critical that you do not perform the same action twice. Reddit has been known to send HTTP server error statuses even while successfully handling the request. Therefore, Retry_manager cannot guarantee that a request had no effect before retrying it - it just trusts Reddit when it says that there was an error.

Transient and non-transient errors

A transient error is an error that we expect to resolve without changes to the API parameters. We operationalize this as

  • any exception raised by the Cohttp client module; or
  • any HTTP response with a server error status code (500-599).

Example: Transient error. Reddit responds to a request with 503 Service Unavailable. We expect that service will eventually be restored, and the same request will then succeed. This is a transient error.

Example: Non-transient error. Reddit responds to a request with 403 Forbidden. We expect that the request will not succeed unless either (a) the request is modified to no longer reference content to which the user does not have access; or (b) the user's permissions are modified outside of this request.

type t
val create : Connection.t -> t
module Non_transient_error : sig ... end
val call : t -> 'a Reddit_api_kernel.Endpoint.t -> ('a, Non_transient_error.t) Async.Deferred.Result.t

call t f immediately calls f unless the last result of such a call was a transient error. In the latter case, all calls block, and call periodically calls a read-only API endpoint until service is restored.

val yield_until_reddit_available : t -> unit Async.Deferred.t

yield_until_reddit_available returns immediately if there is no known transient error; it never causes an HTTP request.