Small utility to extract used metrics from promql queries

go.mod

module prom-stat

go 1.21.1

require github.com/prometheus/prometheus v0.47.2

require (
	github.com/beorn7/perks v1.0.1 // indirect
	github.com/cespare/xxhash/v2 v2.2.0 // indirect
	github.com/dennwc/varint v1.0.0 // indirect
	github.com/go-kit/log v0.2.1 // indirect
	github.com/go-logfmt/logfmt v0.6.0 // indirect
	github.com/gogo/protobuf v1.3.2 // indirect
	github.com/golang/protobuf v1.5.3 // indirect
	github.com/grafana/regexp v0.0.0-20221122212121-6b5c0a4cb7fd // indirect
	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
	github.com/pkg/errors v0.9.1 // indirect
	github.com/prometheus/client_golang v1.16.0 // indirect
	github.com/prometheus/client_model v0.4.0 // indirect
	github.com/prometheus/common v0.44.0 // indirect
	github.com/prometheus/procfs v0.11.0 // indirect
	go.uber.org/atomic v1.11.0 // indirect
	golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 // indirect
	golang.org/x/sys v0.10.0 // indirect
	google.golang.org/protobuf v1.31.0 // indirect
)

main.go

package main

import (
	"bufio"
	"fmt"
	"github.com/prometheus/prometheus/promql/parser"
	"os"
)

func main() {
	metricSet := make(map[string]struct{}) // To remove duplicates
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		line := scanner.Text()
		extractMetrics(line, metricSet)
	}

	if err := scanner.Err(); err != nil {
		fmt.Println("Error reading from stdin:", err)
	}

	for metric := range metricSet {
		fmt.Println(metric)
	}
}

func extractMetrics(query string, metricSet map[string]struct{}) {
	expr, err := parser.ParseExpr(query)
	if err != nil {
		fmt.Printf("Error parsing query: %s, error: %v\n", query, err)
		return
	}

	parser.Inspect(expr, func(node parser.Node, path []parser.Node) error {
		switch n := node.(type) {
		case *parser.VectorSelector:
			metricSet[n.Name] = struct{}{}
		}
		return nil
	})
}

main_test.go

package main

import "testing"

func TestExtractMetrics(t *testing.T) {
	tests := []struct {
		query    string
		expected []string
	}{
		{
			query:    `max by (name, exported_namespace, namespace, condition) (certmanager_certificate_ready_status{condition!="True"} == 1)`,
			expected: []string{"certmanager_certificate_ready_status"},
		},
		{
			query:    `min by (cluster, namespace, priority, poddisruptionbudget) (kube_poddisruptionbudget_status_pod_disruptions_allowed) == 0`,
			expected: []string{"kube_poddisruptionbudget_status_pod_disruptions_allowed"},
		},
		{
			query:    `sum by (destination_service_name, destination_service_namespace, priority) (rate(istio_requests_total{reporter="source"}[5m]))`,
			expected: []string{"istio_requests_total"},
		},
		{
			query:    `sum without (app_kubernetes_io_name, kubernetes_namespace, annotation_service_bare_id_priority) (label_replace(label_replace(probe_success < 1, "ingress", "$1", "app_kubernetes_io_name", "(.*)"), "namespace", "$1", "kubernetes_namespace", "(.*)") * on (namespace, ingress) group_left (priority) topk by (namespace, ingress) (1, label_replace(kube_ingress_annotations, "priority", "$1", "annotation_service_bare_id_priority", "(.*)")))`,
			expected: []string{"probe_success", "kube_ingress_annotations"},
		},
		// ... add more tests as needed
	}

	for _, test := range tests {
		metricSet := make(map[string]struct{})
		extractMetrics(test.query, metricSet)

		if len(metricSet) != len(test.expected) {
			t.Errorf("Query: %s, Expected %d metrics, got %d", test.query, len(test.expected), len(metricSet))
			continue
		}

		for _, exp := range test.expected {
			if _, exists := metricSet[exp]; !exists {
				t.Errorf("Query: %s, Expected metric %s not found", test.query, exp)
			}
		}
	}
}