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Moving averages.

This module implements bandwidth counters based on (cumulative) exponential moving average. Each counter is identified by an integer. They are stored in an internal hash table.

See i.e. https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average for the algorithm.

type t

Type of one bandwidth counter.

type state

Internal state of the worker handling a family of counters.

val fresh_state : id:string -> refresh_interval:float -> state

fresh_state ~id ~refresh_interval initializes the state of a worker handling a family of counter. The worker wakes up every refresh_interval seconds. id is a string identifier used for distinguishing distinct Moving_average workers..

val create : state -> init:int -> alpha:float -> t

create state ~init ~alpha is a counter with initial value init and factor alpha. The counter is added to the state. It is not removed automatically: it must be removed manually.

val destroy : state -> t -> unit

destroy state -> t removes counter t from the internal state.

val add : t -> int -> unit

add state t v adds v to the counter t.

val on_update : state -> (unit -> unit) -> unit

on_update state f registers f to be called on each update of the internal worker associated to state.

val updated : state -> unit Lwt_condition.t

updated state is a condition variable that gets signaled on each update of the internal worker..

type stat = {
  1. total : int64;
  2. average : int;
val stat : t -> stat

stat t is a stat record reflecting the state of t at the time of the call.