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prometheus.ml
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open! Astring open! Asetmap module type NAME_SPEC = sig val valid : Re.re end module type NAME = sig type t = private string val v : string -> t val pp : t Fmt.t val compare : t -> t -> int end module Name(N : NAME_SPEC) : NAME = struct type t = string let v name = if not (Re.execp N.valid name) then failwith (Fmt.strf "Invalid name %S" name); name let compare = String.compare let pp = Fmt.string end let alphabet = Re.(alt [ rg 'a' 'z'; rg 'A' 'Z' ]) module LabelName = struct (* "^[a-zA-Z_][a-zA-Z0-9_]*$" *) let start = Re.alt [ alphabet; Re.char '_' ] let rest = Re.alt [ start; Re.digit ] include Name(struct let valid = Re.compile @@ Re.seq [ Re.bos; start; Re.rep rest; Re.eos] end) end module MetricName = struct (* "^[a-zA-Z_:][a-zA-Z0-9_:]*$" *) let start = Re.alt [ LabelName.start; Re.char ':' ] let rest = Re.alt [ start; Re.digit ] include Name(struct let valid = Re.compile @@ Re.seq [ Re.bos; start; Re.rep rest; Re.eos] end) end type metric_type = | Counter | Gauge | Summary | Histogram module LabelSet = struct type t = string list let compare (a:t) (b:t) = compare a b end module LabelSetMap = Map.Make(LabelSet) module MetricInfo = struct type t = { name : MetricName.t; metric_type : metric_type; help : string; label_names : LabelName.t list; } let pp_opt () = function | None -> "" | Some v -> v ^ "_" let v ~help ?(label_names=[]) ~metric_type ?namespace ?subsystem name = let name = Printf.sprintf "%a%a%s" pp_opt namespace pp_opt subsystem name in { name = MetricName.v name; metric_type; help; label_names; } let compare a b = MetricName.compare a.name b.name end module MetricFamilyMap = Map.Make(MetricInfo) module Sample_set = struct type sample = { ext : string; value : float; bucket : (LabelName.t * float) option; } type t = sample list let sample ?(ext="") ?bucket value = { ext; value; bucket } end module CollectorRegistry = struct type t = { mutable metrics : (unit -> Sample_set.t LabelSetMap.t) MetricFamilyMap.t; mutable pre_collect : (unit -> unit) list; } type snapshot = Sample_set.t LabelSetMap.t MetricFamilyMap.t let create () = { metrics = MetricFamilyMap.empty; pre_collect = []; } let default = create () let register_pre_collect t f = t.pre_collect <- f :: t.pre_collect let register t info collector = if MetricFamilyMap.mem info t.metrics then failwith (Fmt.strf "%a already registered" MetricName.pp info.MetricInfo.name); t.metrics <- MetricFamilyMap.add info collector t.metrics let collect t = List.iter (fun f -> f ()) t.pre_collect; MetricFamilyMap.map (fun f -> f ()) t.metrics end module type METRIC = sig type family type t val v_labels : label_names:string list -> ?registry:CollectorRegistry.t -> help:string -> ?namespace:string -> ?subsystem:string -> string -> family val labels : family -> string list -> t val v_label : label_name:string -> ?registry:CollectorRegistry.t -> help:string -> ?namespace:string -> ?subsystem:string -> string -> (string -> t) val v : ?registry:CollectorRegistry.t -> help:string -> ?namespace:string -> ?subsystem:string -> string -> t end module type CHILD = sig type t val create : unit -> t val values : t -> Sample_set.t val metric_type : metric_type val validate_label : string -> unit end module Metric(Child : CHILD) : sig include METRIC with type t = Child.t end = struct type family = { metric : MetricInfo.t; mutable children : Child.t LabelSetMap.t; } type t = Child.t let collect t = LabelSetMap.map Child.values t.children let v_labels ~label_names ?(registry=CollectorRegistry.default) ~help ?namespace ?subsystem name = List.iter Child.validate_label label_names; let label_names = List.map LabelName.v label_names in let metric = MetricInfo.v ~metric_type:Child.metric_type ~help ~label_names ?namespace ?subsystem name in let t = { metric; children = LabelSetMap.empty; } in CollectorRegistry.register registry metric (fun () -> collect t); t let labels t label_values = assert (List.length t.metric.MetricInfo.label_names = List.length label_values); match LabelSetMap.find label_values t.children with | Some child -> child | None -> let child = Child.create () in t.children <- LabelSetMap.add label_values child t.children; child let v_label ~label_name ?registry ~help ?namespace ?subsystem name = let family = v_labels ~label_names:[label_name] ?registry ~help ?namespace ?subsystem name in fun x -> labels family [x] let v ?registry ~help ?namespace ?subsystem name = let family = v_labels ~help ?registry ?namespace ?subsystem name ~label_names:[] in labels family [] end module Counter = struct include Metric(struct type t = float ref let create () = ref 0.0 let values t = [Sample_set.sample !t] let metric_type = Counter let validate_label _ = () end) let inc_one t = t := !t +. 1.0 let inc t v = assert (v >= 0.0); t := !t +. v end module Gauge = struct include Metric(struct type t = float ref let create () = ref 0.0 let values t = [Sample_set.sample !t] let metric_type = Gauge let validate_label _ = () end) let inc t v = t := !t +. v let inc_one t = inc t 1.0 let dec t x = inc t (-. x) let dec_one t = dec t 1.0 let set t v = t := v let track_inprogress t fn = inc_one t; Lwt.finalize fn (fun () -> dec_one t; Lwt.return_unit) let time t gettimeofday fn = let start = gettimeofday () in Lwt.finalize fn (fun () -> let finish = gettimeofday () in inc t (finish -. start); Lwt.return_unit ) end module Summary = struct module Child = struct type t = { mutable count : float; mutable sum : float; } let create () = { count = 0.0; sum = 0.0 } let values t = [ Sample_set.sample ~ext:"_sum" t.sum; Sample_set.sample ~ext:"_count" t.count; ] let metric_type = Summary let validate_label = function | "quantile" -> failwith "Can't use special label 'quantile' in summary" | _ -> () end include Metric(Child) let observe t v = let open Child in t.count <- t.count +. 1.0; t.sum <- t.sum +. v let time t gettimeofday fn = let start = gettimeofday () in Lwt.finalize fn (fun () -> let finish = gettimeofday () in observe t (finish -. start); Lwt.return_unit ) end module Histogram_spec = struct type t = float array (* Upper bounds *) let make at_index_f count = let real_at_index i = if i >= count then infinity else at_index_f i in Array.init (count + 1) real_at_index let of_linear start interval count = let at_index i = let f = float_of_int i in start +. (interval *. f) in make at_index count let of_exponential start factor count = let at_index i = let multiplier = factor ** (float_of_int i) in start *. multiplier in make at_index count let of_list lst = let length = List.length lst in make (List.nth lst) length (* The index at which to record a value [v]. *) let index t v = let rec aux index = if v <= t.(index) then index else aux (index + 1) in aux 0 end module type BUCKETS = sig val spec : Histogram_spec.t end module type HISTOGRAM = sig include METRIC val observe : t -> float -> unit val time : t -> (unit -> float) -> (unit -> 'a Lwt.t) -> 'a Lwt.t end let bucket_label = LabelName.v "le" module Histogram (Buckets : BUCKETS) = struct module Child = struct type t = { upper_bounds : Histogram_spec.t; counts : float array; mutable sum : float; } let create () = let count = Array.length Buckets.spec in let counts = Array.make count 0. in { upper_bounds = Buckets.spec; counts; sum = 0. } let values t = let count = Array.length t.counts in let rec fold val_acc acc index = if index = count then Sample_set.sample ~ext:"_sum" t.sum :: Sample_set.sample ~ext:"_count" val_acc :: acc else let val_acc = t.counts.(index) +. val_acc in let bucket = (bucket_label, t.upper_bounds.(index)) in let acc = Sample_set.sample ~ext:"_bucket" val_acc ~bucket :: acc in fold val_acc acc (index + 1) in fold 0. [] 0 let metric_type = Histogram let validate_label = function | "le" -> failwith "Can't use special label 'le' in histogram" | _ -> () end include Metric(Child) let observe t v = let open Child in let index = Histogram_spec.index t.upper_bounds v in t.counts.(index) <- t.counts.(index) +. 1.; t.sum <- t.sum +. v let time t gettimeofday fn = let start = gettimeofday () in Lwt.finalize fn (fun () -> let finish = gettimeofday () in observe t (finish -. start); Lwt.return_unit ) end module DefaultHistogram = Histogram ( struct let spec = Histogram_spec.of_list [0.005; 0.01; 0.025; 0.05; 0.075; 0.1 ; 0.25 ; 0.5; 0.75 ; 1. ; 2.5 ; 5.; 7.5 ; 10. ] end)