API reference

Prometheus text exposition format for Zig: write metrics to any writer, no HTTP.

One value, Writer, over a std.Io.Writer. Its methods are the primitives (help, kind, name, value, line) and the compositions built on them (writeMetric, writeFamily, writeHistogram, and the series form a multi-series histogram family loops).

struct Writer

src

pub const Writer = @import("writer.zig").Writer

Fields

out: *Io.Writer

Functions

`pub fn init(out: *Io.Writer) Writer`

src

`pub fn help(self: Writer, comptime metric_name: []const u8, text: []const u8) Io.Writer.Error!void`

src

# HELP name text, with the text escaped. An empty text writes the line without a trailing space.

`pub fn kind(self: Writer, comptime metric_name: []const u8, type_kind: Kind) Io.Writer.Error!void`

src

# TYPE name kind.

`pub fn name(self: Writer, comptime name_text: []const u8, labels: anytype) Io.Writer.Error!void`

src

name{label="value",...} with no trailing space. A struct gives its fields in order; a tuple of structs gives their fields in sequence, which is how a caller adds a label of its own to one it already has.

`pub fn value(self: Writer, value_text: anytype) Io.Writer.Error!void`

src

value and the newline that ends the record. An integer type is written as decimal; a float follows the expfmt rule in value.zig.

`pub fn line(self: Writer, bytes: []const u8) Io.Writer.Error!void`

src

Bytes the caller already formatted. Written as given: no newline, no escaping.

`pub fn writeMetric( self: Writer, comptime name_text: []const u8, label_values: anytype, value_text: anytype, ) Io.Writer.Error!void`

src

One sample line: the name, the labels, the value, and the newline.

`pub fn writeFamily(self: Writer, comptime m: Metric) Io.Writer.Error!FamilyWriter(m)`

src

# HELP, # TYPE, and the handle its samples go through.

`pub fn writeHistogram( self: Writer, comptime m: Metric, label_values: anytype, limits: []const f64, counts: []const u64, sum: anytype, count: u64, ) Io.Writer.Error!void`

src

A whole classic histogram for one label set: the header and one series.

A family with more than one series cannot use this twice, because each call writes # HELP and # TYPE again and the parser rejects the second. Write writeFamily once and loop FamilyWriter.writeHistogramSeries instead.

enum Kind

src

pub const Kind = @import("writer.zig").Kind

The # TYPE line's vocabulary.

Fields

counter counter

gauge gauge

histogram histogram

untyped untyped

struct Metric

src

pub const Metric = @import("writer.zig").Metric

One family: the name, its kind, and the help text. The name and kind are read at comptime, which is where a bad one is caught.

Fields

name: []const u8

kind: Kind

help: []const u8 = ""

type fn FamilyWriter

src

pub const FamilyWriter = @import("writer.zig").FamilyWriter

A family's samples, from the value writeFamily handed back. It carries the family's name, which is why the series form hangs off it: a bare Writer has nowhere to get one.

Fields

writer: Writer

Functions

`pub fn write(self: Self, label_values: anytype, value_text: anytype) Io.Writer.Error!void`

src

`pub fn writeHistogramSeries( self: Self, label_values: anytype, limits: []const f64, counts: []const u64, sum: anytype, count: u64, ) Io.Writer.Error!void`

src

One histogram series: the bucket lines, _sum, and _count, with no header. A family with more than one series writes help and kind once through writeFamily and then calls this per series.

sum is anytype so a caller whose sum is a u64 keeps every digit; a f64 cannot hold one above 2^53.