tezos-requester 12.3 · OCaml Package

A helper to avoid having to use the full-fledged Requester.Make * functor. We take the Requester.REQUEST module as parameter (instead * of hardcoding the use of Simple_request), because * callers that use Simple_request likely want to observe * the underlying effects (see the ref in Simple_request) and hence * want to pass their own instance. * * Like Requester.Make, this returns an instance of FULL_REQUESTER. * Note that, contrary to a production requester, the instance returned * by this functor does not use the disk, it runs entirely in memory.

Parameters

module H : Requester.HASH

module P : PARAMETERS with type key = H.t

module R : Requester.REQUEST with type param = unit and type key = H.t

Signature

include Requester.REQUESTER
  with type key = H.t
  with type value = P.value
  with type param = bool

type t

type key = H.t

The index key

type value = P.value

The indexed data

type param = bool

validation clue

val known : t -> key -> bool Lwt.t

know t k returns true iff the key is present in the memory table or the disk.

type Tezos_base__TzPervasives.error +=

| Missing_data of key

type Tezos_base__TzPervasives.error +=

| Canceled of key

type Tezos_base__TzPervasives.error +=

| Timeout of key

val read : 
  t ->
  key ->
  (value, Tezos_error_monad.TzCore.error list) result Lwt.t

Return value if it is found in-memory, or else on disk. Otherwise fail with error Missing_data.

val read_opt : t -> key -> value option Lwt.t

Same as read but returns None if not found.

val fetch : 
  t ->
  ?peer:Tezos_base.P2p_peer.Id.t ->
  ?timeout:Tezos_base.Time.System.Span.t ->
  key ->
  param ->
  (value, Tezos_error_monad.TzCore.error list) result Lwt.t

fetch t ?peer ?timeout k param returns the value when it is known. It can fail with Timeout k if timeout is provided and the value isn't know before the timeout expires. It can fail with Cancel if the request is canceled.

The key is first looked up in memory, then on disk. If not present and not already requested, it schedules a request, and blocks until the requester is notified with notify. param is used to validate the notified value once it is received. (see also PROBE and notify).

Requests are re-sent via a 1.5 exponential back-off, with initial delay set to Request.initial_delay. If the function is called multiple time with the same key but with distinct peers, the internal scheduler randomly chooses the requested peer (at each retry).

val clear_or_cancel : t -> key -> unit

Remove the data from the memory table if present. Otherwise cancel all pending requests. Any pending fetch promises are resolved with the error Canceled.

type store = Disk_memory_table(P).store

The "disk" storage

type request_param = unit

Configuration parameter to the Request service

type notified_value = P.value

type of values notified to the requester

val pending : t -> key -> bool

pending t k returns true iff the key status is pending

val watch : t -> (key * value) Lwt_stream.t * Lwt_watcher.stopper

Monitor all the fetched data. A given data will appear only once.

val inject : t -> key -> value -> bool Lwt.t

inject t k v returns false if k is already present in the memory table or in the disk, or has already been requested. Otherwise it updates the memory table and return true

val notify : 
  t ->
  Tezos_base.P2p_peer.Id.t ->
  key ->
  notified_value ->
  unit Lwt.t

notify t peer k nv notifies the requester that a value has been received for key k, from peer peer. nv is a *notified value*. The notified value is validated using Probe.probe, and the param provided at fetching time (see PROBE). If valid, the memory table is updated and all promises waiting on this key are resolved.

If the key is not pending the notification is ignored.

val memory_table_length : t -> int

memory_table_length t returns the number of keys either known or pending in the memory table of t

val pending_requests : t -> int

Returns the number of requests currently pending

val create : 
  ?random_table:bool ->
  ?global_input:(key * value) Lwt_watcher.input ->
  request_param ->
  store ->
  t

create ?random_table ?global_input r s creates a requester. r is the configuration parameter passed to Request functions.

The value for random_table determines whether the underlying hashtable randomises its hash (see Stdlib.Hashtbl.create and specifically the documentation of the random parameter). The default depends on environment variables and Stdlib.Hashtbl.randomize has been called.

val shutdown : t -> unit Lwt.t

package tezos-requester

Parameters

Signature