Table of Go Metrics Exposed by Prometheus under Different Rules¶

package main

import (
    "bytes"
    "fmt"
    "os"
    "runtime"

    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/collectors"
)

func main() {
    pkgOfferedRules := []collectors.GoRuntimeMetricsRule{
        collectors.MetricsGC,
        collectors.MetricsMemory,
        collectors.MetricsScheduler,
        collectors.MetricsDebug,
    }

    type metricTyp struct {
        Name, Help string
    }

    set := make(map[int][]metricTyp)
    for i := 0; i <= len(pkgOfferedRules); i++ {
        reg := prometheus.NewPedanticRegistry()
        reg.MustRegister(collectors.NewGoCollector(
            collectors.WithGoCollectorRuntimeMetrics(
                pkgOfferedRules[:i]...,
            ),
        ))

        result, err := reg.Gather()
        if err != nil {
            panic(err)
        }
        got := []metricTyp{}
        for _, r := range result {
            got = append(got, metricTyp{
                Name: r.GetName(),
                Help: r.GetHelp(),
            })
        }
        set[i] = got
    }

    // retrieve where does the metric come from.
    m := make(map[metricTyp]int)
    for i := 0; i <= len(pkgOfferedRules); i++ {
        for _, metric := range set[i] {
            if _, exists := m[metric]; exists {
                // it's added by earlier rule
                continue
            }
            m[metric] = i
        }
    }
    metricsList := make([]metricTyp, 0, len(m))
    for metric := range m {
        metricsList = append(metricsList, metric)
    }

    finalListM := map[int][]metricTyp{}
    for _, metric := range metricsList {
        addedBy := m[metric]
        if _, exists := finalListM[addedBy]; !exists {
            finalListM[addedBy] = []metricTyp{}
        }
        finalListM[addedBy] = append(finalListM[addedBy], metric)
    }

    var buf bytes.Buffer
    buf.WriteString("# Table of Go Metrics Exposed by Prometheus under Different Rules\n")

    help := fmt.Sprintf(`

Prometheus golang_client helps to expose go runtime/metrics so you can collect it,
and the block below shows a short example.

collectors.WithGoCollectorRuntimeMetrics accepts various rules and prometheus collector package
also offers several options.

This page aims to mitigate 2 painpoints:

1. conversion from runtime metrics to prometheus exposed metrics.

The names are very similar but with different format change, the table below shows
the exposed go metrics by prometheus.

2. quickly choose rules to expose specific metrics.

Sometimes you don't want to expose all metrics but a part of them, then users need to check
the rules offered by collector package and use it, but then they may also want to understand what are the metrics exposed by the way.
The table helps to check all metrics exposed by a certain rule.

%sgo
reg := prometheus.NewPedanticRegistry()
reg.MustRegister(collectors.NewGoCollector(
    collectors.WithGoCollectorRuntimeMetrics(
        collectors.MetricsGC,
    ),
))
%s
`, "```", "```")
    buf.WriteString(help)
    buf.WriteString(fmt.Sprintf("\nTable is generated by Go version %s, and using rule `collectors.MetricsAll` will get all metrics listed below.\n\n", runtime.Version()))
    for i := 0; i <= len(pkgOfferedRules); i++ {
        addedBy := "default"
        optMetricsList := finalListM[i]
        switch m[optMetricsList[0]] {
        case 1:
            addedBy = "collectors.MetricsGC"
        case 2:
            addedBy = "collectors.MetricsMemory"
        case 3:
            addedBy = "collectors.MetricsScheduler"
        case 4:
            addedBy = "collectors.MetricsDebug"
        }
        buf.WriteString(fmt.Sprintf("\n## Metrics added by %s\n\n", addedBy))
        buf.WriteString("| Metric Name      |  Help |\n|:-----------------|:---------|\n")
        for _, metric := range optMetricsList {
            buf.WriteString(fmt.Sprintf("| %s | %s |\n", metric.Name, metric.Help))
        }
        buf.WriteString("\n")
    }

    err := os.WriteFile("METRICS_ADDED_BY.md", buf.Bytes(), 0644)
    if err != nil {
        panic(err)
    }
}