--[[ This module implements a subset of the OpenMetrics Internet Draft version 00. URL: https://tools.ietf.org/html/draft-richih-opsawg-openmetrics-00 The following metric types are supported: - Counter - Gauge - Histogram - Summary It is used by util.statsd and util.statistics to provite the OpenMetrics API. To understand what this module is about, it is useful to familiarize oneself with the terms MetricFamily, Metric, LabelSet, Label and MetricPoint as defined in the I-D linked above. --]] -- metric constructor interface: -- metric_ctor(..., family_name, labels, extra) local time = require "util.time".now; local select = select; local array = require "util.array"; local log = require "util.logger".init("util.openmetrics"); local new_multitable = require "util.multitable".new; local iter_multitable = require "util.multitable".iter; -- BEGIN of Utility: "metric proxy" -- This allows to wrap a MetricFamily in a proxy which only provides the -- `with_labels` and `with_partial_label` methods. This allows to pre-set one -- or more labels on a metric family. This is used in particular via -- `with_partial_label` by the moduleapi in order to pre-set the `host` label -- on metrics created in non-global modules. local metric_proxy_mt = {} metric_proxy_mt.__index = metric_proxy_mt local function new_metric_proxy(metric_family, with_labels_proxy_fun) return { _family = metric_family, with_labels = function(self, ...) return with_labels_proxy_fun(self._family, ...) end; with_partial_label = function(self, label) return new_metric_proxy(self._family, function(family, ...) return family:with_labels(label, ...) end) end } end -- END of Utility: "metric proxy" local function render_histogram_le(v) if v == 1/0 then -- I-D-00: 4.1.2.2.1: -- Exposers MUST produce output for positive infinity as +Inf. return "+Inf" end return string.format("%.14g", v) end -- BEGIN of generic MetricFamily implementation local metric_family_mt = {} metric_family_mt.__index = metric_family_mt local function histogram_metric_ctor(orig_ctor, buckets) return function(family_name, labels, extra) return orig_ctor(buckets, family_name, labels, extra) end end local function new_metric_family(backend, type_, family_name, unit, description, label_keys, extra) local metric_ctor = assert(backend[type_], "statistics backend does not support "..type_.." metrics families") local labels = label_keys or {} local user_labels = #labels if type_ == "histogram" then local buckets = extra and extra.buckets if not buckets then error("no buckets given for histogram metric") end buckets = array(buckets) buckets:push(1/0) -- must have +inf bucket metric_ctor = histogram_metric_ctor(metric_ctor, buckets) end local data if #labels == 0 then data = metric_ctor(family_name, nil, extra) else data = new_multitable() end local mf = { family_name = family_name, data = data, type_ = type_, unit = unit, description = description, user_labels = user_labels, label_keys = labels, extra = extra, _metric_ctor = metric_ctor, } setmetatable(mf, metric_family_mt); return mf end function metric_family_mt:new_metric(labels) return self._metric_ctor(self.family_name, labels, self.extra) end function metric_family_mt:clear() for _, metric in self:iter_metrics() do metric:reset() end end function metric_family_mt:with_labels(...) local count = select('#', ...) if count ~= self.user_labels then error("number of labels passed to with_labels does not match number of label keys") end if count == 0 then return self.data end local metric = self.data:get(...) if not metric then local values = table.pack(...) metric = self:new_metric(values) values[values.n+1] = metric self.data:set(table.unpack(values, 1, values.n+1)) end return metric end function metric_family_mt:with_partial_label(label) return new_metric_proxy(self, function (family, ...) return family:with_labels(label, ...) end) end function metric_family_mt:iter_metrics() if #self.label_keys == 0 then local done = false return function() if done then return nil end done = true return {}, self.data end end local searchkeys = {}; local nlabels = #self.label_keys for i=1,nlabels do searchkeys[i] = nil; end local it, state = iter_multitable(self.data, table.unpack(searchkeys, 1, nlabels)) return function(_s) local label_values = table.pack(it(_s)) if label_values.n == 0 then return nil, nil end local metric = label_values[label_values.n] label_values[label_values.n] = nil label_values.n = label_values.n - 1 return label_values, metric end, state end -- END of generic MetricFamily implementation -- BEGIN of MetricRegistry implementation -- Helper to test whether two metrics are "equal". local function equal_metric_family(mf1, mf2) if mf1.type_ ~= mf2.type_ then return false end if #mf1.label_keys ~= #mf2.label_keys then return false end -- Ignoring unit here because in general it'll be part of the name anyway -- So either the unit was moved into/out of the name (which is a valid) -- thing to do on an upgrade or we would expect not to see any conflicts -- anyway. --[[ if mf1.unit ~= mf2.unit then return false end ]] for i, key in ipairs(mf1.label_keys) do if key ~= mf2.label_keys[i] then return false end end return true end -- If the unit is not empty, add it to the full name as per the I-D spec. local function compose_name(name, unit) local full_name = name if unit and unit ~= "" then full_name = full_name .. "_" .. unit end -- TODO: prohibit certain suffixes used by metrics if where they may cause -- conflicts return full_name end local metric_registry_mt = {} metric_registry_mt.__index = metric_registry_mt local function new_metric_registry(backend) local reg = { families = {}, backend = backend, } setmetatable(reg, metric_registry_mt) return reg end function metric_registry_mt:register_metric_family(name, metric_family) local existing = self.families[name]; if existing then if not equal_metric_family(metric_family, existing) then -- We could either be strict about this, or replace the -- existing metric family with the new one. -- Being strict is nice to avoid programming errors / -- conflicts, but causes issues when a new version of a module -- is loaded. -- -- We will thus assume that the new metric is the correct one; -- That is probably OK because unless you're reaching down into -- the util.openmetrics or core.statsmanager API, your metric -- name is going to be scoped to `prosody_mod_$modulename` -- anyway and the damage is thus controlled. -- -- To make debugging such issues easier, we still log. log("debug", "replacing incompatible existing metric family %s", name) -- Below is the code to be strict. --error("conflicting declarations for metric family "..name) else return existing end end self.families[name] = metric_family return metric_family end function metric_registry_mt:gauge(name, unit, description, labels, extra) name = compose_name(name, unit) local mf = new_metric_family(self.backend, "gauge", name, unit, description, labels, extra) mf = self:register_metric_family(name, mf) return mf end function metric_registry_mt:counter(name, unit, description, labels, extra) name = compose_name(name, unit) local mf = new_metric_family(self.backend, "counter", name, unit, description, labels, extra) mf = self:register_metric_family(name, mf) return mf end function metric_registry_mt:histogram(name, unit, description, labels, extra) name = compose_name(name, unit) local mf = new_metric_family(self.backend, "histogram", name, unit, description, labels, extra) mf = self:register_metric_family(name, mf) return mf end function metric_registry_mt:summary(name, unit, description, labels, extra) name = compose_name(name, unit) local mf = new_metric_family(self.backend, "summary", name, unit, description, labels, extra) mf = self:register_metric_family(name, mf) return mf end function metric_registry_mt:get_metric_families() return self.families end -- END of MetricRegistry implementation -- BEGIN of general helpers for implementing high-level APIs on top of OpenMetrics local function timed(metric) local t0 = time() local submitter = assert(metric.sample or metric.set, "metric type cannot be used with timed()") return function() local t1 = time() submitter(metric, t1-t0) end end -- END of general helpers return { new_metric_proxy = new_metric_proxy; new_metric_registry = new_metric_registry; render_histogram_le = render_histogram_le; timed = timed; }