Source file RPC_client_unix.ml

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type attempt_event = {attempt : int; delay : float; text : string}

module Attempt_logging = Internal_event.Make (struct
  type t = attempt_event

  let section = None

  let name = "rpc_http_attempt"

  let doc = "Error emitted when an HTTP request returned a 502 error."

  let encoding =
    Data_encoding.(
      conv
        (fun {attempt; delay; text} -> (attempt, delay, text))
        (fun (attempt, delay, text) -> {attempt; delay; text})
        (obj3 (req "attempt" int8) (req "delay" float) (req "text" string)))

  let pp ~all_fields:_ ~block:_ f {attempt; delay; text} =
    Format.fprintf
      f
      "Attempt number %d/10, will retry after %g seconds.\n\
       Original body follows.\n\
       %s"
      attempt
      delay
      text

  let level = Internal_event.Error
end)

module RetryClient :
  Cohttp_lwt.S.Client with type ctx = Cohttp_lwt_unix.Net.ctx = struct
  include Cohttp_lwt_unix.Client

  let clone_body = function `Stream s -> `Stream (Lwt_stream.clone s) | x -> x

  let call ?ctx ?headers ?body ?chunked meth uri =
    let rec call_and_retry_on_502 attempt delay =
      let open Lwt_syntax in
      let* response, ansbody =
        Cohttp_lwt_unix.Client.call ?ctx ?headers ?body ?chunked meth uri
      in
      let status = Cohttp.Response.status response in
      match status with
      | `Bad_gateway ->
          let log_ansbody = clone_body ansbody in
          let* text = Cohttp_lwt.Body.to_string log_ansbody in
          let* _ = Attempt_logging.emit {attempt; delay; text} in
          if attempt >= 10 then return (response, ansbody)
          else
            let* () = Lwt_unix.sleep delay in
            call_and_retry_on_502 (attempt + 1) (delay +. 0.1)
      | _ -> return (response, ansbody)
    in
    call_and_retry_on_502 1 0.
end

include RPC_client.Make (Resto_cohttp_client.Client.OfCohttp (RetryClient))