From 7309c9ba22a2b07bae182e5ea8b10aa214be13fd Mon Sep 17 00:00:00 2001
From: Anna Kapuscinska <anna@isovalent.com>
Date: Sun, 23 Jun 2024 19:32:26 +0100
Subject: [PATCH] mapmetrics,observer: Refactor metrics collector

Use new helpers from pkg/metrics to define custom metrics and collector.

Signed-off-by: Anna Kapuscinska <anna@isovalent.com>
---
 pkg/metrics/mapmetrics/mapmetrics.go | 30 +++++++------
 pkg/observer/observer_stats.go       | 67 +++++++---------------------
 2 files changed, 33 insertions(+), 64 deletions(-)

diff --git a/pkg/metrics/mapmetrics/mapmetrics.go b/pkg/metrics/mapmetrics/mapmetrics.go
index c4361d97162..410a91ef982 100644
--- a/pkg/metrics/mapmetrics/mapmetrics.go
+++ b/pkg/metrics/mapmetrics/mapmetrics.go
@@ -6,27 +6,29 @@ package mapmetrics
 import (
 	"github.com/cilium/tetragon/pkg/metrics"
 	"github.com/cilium/tetragon/pkg/metrics/consts"
-	"github.com/prometheus/client_golang/prometheus"
 )
 
+var MapLabel = metrics.ConstrainedLabel{
+	Name: "map",
+	// These are maps which usage we monitor, not maps from which we read
+	// metrics. Metrics are read from separate maps suffixed with "_stats".
+	Values: []string{"execve_map", "tg_execve_joined_info_map"},
+}
+
 var (
-	MapSize = metrics.NewBPFGauge(prometheus.NewDesc(
-		prometheus.BuildFQName(consts.MetricsNamespace, "", "map_entries"),
+	MapSize = metrics.MustNewCustomGauge(metrics.NewOpts(
+		consts.MetricsNamespace, "", "map_entries",
 		"The total number of in-use entries per map.",
-		[]string{"map"}, nil,
+		nil, []metrics.ConstrainedLabel{MapLabel}, nil,
 	))
-	MapCapacity = metrics.NewBPFGauge(prometheus.NewDesc(
-		prometheus.BuildFQName(consts.MetricsNamespace, "", "map_capacity"),
+	MapCapacity = metrics.MustNewCustomGauge(metrics.NewOpts(
+		consts.MetricsNamespace, "", "map_capacity",
 		"Capacity of a BPF map. Expected to be constant.",
-		[]string{"map"}, nil,
+		nil, []metrics.ConstrainedLabel{MapLabel}, nil,
 	))
-	MapErrors = metrics.NewBPFCounter(prometheus.NewDesc(
-		prometheus.BuildFQName(consts.MetricsNamespace, "", "map_errors_total"),
+	MapErrors = metrics.MustNewCustomGauge(metrics.NewOpts(
+		consts.MetricsNamespace, "", "map_errors_total",
 		"The number of errors per map.",
-		[]string{"map"}, nil,
+		nil, []metrics.ConstrainedLabel{MapLabel}, nil,
 	))
 )
-
-func InitMetrics(_ *prometheus.Registry) {
-	// custom collectors are registered independently
-}
diff --git a/pkg/observer/observer_stats.go b/pkg/observer/observer_stats.go
index 3b4e7494d77..8849dd0d3ed 100644
--- a/pkg/observer/observer_stats.go
+++ b/pkg/observer/observer_stats.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/cilium/ebpf"
 	"github.com/cilium/tetragon/pkg/logger"
+	"github.com/cilium/tetragon/pkg/metrics"
 	"github.com/cilium/tetragon/pkg/metrics/mapmetrics"
 	"github.com/cilium/tetragon/pkg/option"
 	"github.com/cilium/tetragon/pkg/sensors"
@@ -16,20 +17,19 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-// bpfCollector implements prometheus.Collector. It collects metrics directly from BPF maps.
-type bpfCollector struct{}
-
-func NewBPFCollector() prometheus.Collector {
-	return &bpfCollector{}
-}
-
-func (c *bpfCollector) Describe(ch chan<- *prometheus.Desc) {
-	ch <- mapmetrics.MapSize.Desc()
-	ch <- mapmetrics.MapCapacity.Desc()
-	ch <- mapmetrics.MapErrors.Desc()
+func NewBPFCollector() metrics.CollectorWithInit {
+	return metrics.NewCustomCollector(
+		metrics.CustomMetrics{
+			mapmetrics.MapSize,
+			mapmetrics.MapCapacity,
+			mapmetrics.MapErrors,
+		},
+		collect,
+		collectForDocs,
+	)
 }
 
-func (c *bpfCollector) Collect(ch chan<- prometheus.Metric) {
+func collect(ch chan<- prometheus.Metric) {
 	statsSuffix := "_stats"
 	// Depending on the sensors that are loaded and the dependencies between them,
 	// sensors.AllMaps may have the same map name multiple times. This can cause in
@@ -113,43 +113,10 @@ func updateMapErrors(ch chan<- prometheus.Metric, mapLinkStats *ebpf.Map, name s
 	)
 }
 
-// bpfZeroCollector implements prometheus.Collector. It collects "zero" metrics.
-// It's intended to be used when BPF metrics are not collected, but we still want
-// Prometheus metrics to be exposed.
-type bpfZeroCollector struct {
-	bpfCollector
-}
-
-func NewBPFZeroCollector() prometheus.Collector {
-	return &bpfZeroCollector{
-		bpfCollector: bpfCollector{},
-	}
-}
-
-func (c *bpfZeroCollector) Describe(ch chan<- *prometheus.Desc) {
-	c.bpfCollector.Describe(ch)
-}
-
-func (c *bpfZeroCollector) Collect(ch chan<- prometheus.Metric) {
-	// This list should contain all monitored maps.
-	// These are not maps from which metrics are read in the "real" collector -
-	// the metrics are stored in separate maps suffixed with "_stats".
-	monitoredMaps := []string{
-		"execve_map",
-		"tg_execve_joined_info_map",
-	}
-	for _, m := range monitoredMaps {
-		ch <- mapmetrics.MapSize.MustMetric(
-			0,
-			m,
-		)
-		ch <- mapmetrics.MapCapacity.MustMetric(
-			0,
-			m,
-		)
-		ch <- mapmetrics.MapErrors.MustMetric(
-			0,
-			m,
-		)
+func collectForDocs(ch chan<- prometheus.Metric) {
+	for _, m := range mapmetrics.MapLabel.Values {
+		ch <- mapmetrics.MapSize.MustMetric(0, m)
+		ch <- mapmetrics.MapCapacity.MustMetric(0, m)
+		ch <- mapmetrics.MapErrors.MustMetric(0, m)
 	}
 }