gizlang:metrics

counters, gauges and histograms that every thread of a process can change without a lock or an allocation, and their exposition in the Prometheus text format 0.0.4 (GET /metrics). OTLP push reads the same metrics later; there is one registry of values, the process's atomics.

A metric declares its label values up front: its series set is bounded and known. Each series cell is Task.atomicGlobal of the series identity, so two declarations of the same metric (in two modules or threads) share values. Exposition takes the metrics to show; there is no hidden global list. Values are i64 in the metric's base unit. scale (a power of ten) states how many base units make one exposed unit, so an exposed value is exact decimal text (for example microseconds observed, seconds exposed).

import * as Metrics from "gizlang:metrics";

Types

Series

type Series = { values: Vec<string>; kind: string; bounds: Vec<i64>; cells: Vec<Task.Atomic>; }

One labelled series. Counter and gauge: one cell. Histogram: one cell per bucket (not cumulative), the last for values above every bound, then the sum.

• values: Vec<string>
• kind: string
• bounds: Vec<i64>
• cells: Vec<gizlang_task.Atomic>

Metric

type Metric = { name: string; help: string; kind: string; labels: Vec<string>; scale: i64; bounds: Vec<i64>; series: Vec<Series>; }

A metric: its name, help, kind, label names, scale, histogram bounds and series.

• name: string
• help: string
• kind: string
• labels: Vec<string>
• scale: i64
• bounds: Vec<i64>
• series: Vec<gizlang_metrics.Series>

Functions

counter

function counter(name: string, help: string, labels: Vec<string>, values: Vec<Vec<string>>): Metric throws string

A monotonic count. values lists the label values of each series.

Effects: fail, io.

gauge

function gauge(name: string, help: string, labels: Vec<string>, values: Vec<Vec<string>>, scale: i64): Metric throws string

A value that goes up and down, exposed as value/scale.

Effects: fail, io.

histogram

function histogram(name: string, help: string, labels: Vec<string>, values: Vec<Vec<string>>, bounds: Vec<i64>, scale: i64): Metric throws string

Observations counted in buckets with upper bounds bounds (ascending, in base units), exposed with their sum and count.

Effects: fail, io.

text

function text(metrics: Vec<Metric>): string

The metrics in the Prometheus text exposition format 0.0.4. A histogram's count is the sum of the bucket cells it read, so +Inf and _count agree.

Effects: fail, io.

handler

function handler(metrics: Vec<Metric>): Response

The GET /metrics response.

Effects: fail, io.

Methods

Metric.at

function Metric.at(self: Metric, values: Vec<string>): Option<Series>

The series with these label values. Keep it: the lookup is linear.

Effects: fail.

Series.add

function Series.add(self: Series, n: i64): bool

Add to a counter (n >= 0) or a gauge. False for a histogram or a negative counter step.

Effects: fail, io.

Series.set

function Series.set(self: Series, value: i64): bool

Set a gauge. False for other kinds.

Effects: fail, io.

Series.observe

function Series.observe(self: Series, value: i64): bool

Record one observation in a histogram. False for other kinds.

Effects: fail, io.

Series.value

function Series.value(self: Series): i64

The current value of a counter or gauge, in base units.

Effects: fail, io.