rcmgr: expose resource limits to Prometheus (#3433)

Signed-off-by: sneax <paladesh600@gmail.com>

Author: sneaxhuh

p2p/host/resource-manager/limits_metrics_test.go

@@ -0,0 +1,149 @@
+package rcmgr
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+)
+
+func TestReportSystemLimits(t *testing.T) {
+	// Register the metrics
+	reg := prometheus.NewRegistry()
+	reg.MustRegister(limits)
+
+	// Create a simple limiter with known limits
+	limiter := NewFixedLimiter(ConcreteLimitConfig{
+		system: BaseLimit{
+			Memory:          1024 * 1024 * 1024, // 1GB
+			FD:              256,
+			Conns:           100,
+			ConnsInbound:    50,
+			ConnsOutbound:   50,
+			Streams:         200,
+			StreamsInbound:  100,
+			StreamsOutbound: 100,
+		},
+		transient: BaseLimit{
+			Memory:          512 * 1024 * 1024, // 512MB
+			FD:              128,
+			Conns:           50,
+			ConnsInbound:    25,
+			ConnsOutbound:   25,
+			Streams:         100,
+			StreamsInbound:  50,
+			StreamsOutbound: 50,
+		},
+	})
+
+	// Create a stats reporter
+	reporter, err := NewStatsTraceReporter()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Report the limits
+	reporter.ReportSystemLimits(limiter)
+
+	// Verify that metrics were set
+	metrics, err := reg.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Find the limits metric
+	var limitsMetric *dto.MetricFamily
+	for _, m := range metrics {
+		if m.GetName() == "libp2p_rcmgr_limit" {
+			limitsMetric = m
+			break
+		}
+	}
+
+	if limitsMetric == nil {
+		t.Fatal("limits metric not found")
+	}
+
+	// Verify we have metrics for both system and transient scopes
+	foundSystem := false
+	foundTransient := false
+	for _, metric := range limitsMetric.GetMetric() {
+		for _, label := range metric.GetLabel() {
+			if label.GetName() == "scope" {
+				if label.GetValue() == "system" {
+					foundSystem = true
+				}
+				if label.GetValue() == "transient" {
+					foundTransient = true
+				}
+			}
+		}
+	}
+
+	if !foundSystem {
+		t.Error("system scope limits not reported")
+	}
+	if !foundTransient {
+		t.Error("transient scope limits not reported")
+	}
+
+	// Verify specific limit values
+	expectedLimits := map[string]map[string]float64{
+		"system": {
+			"memory":           1024 * 1024 * 1024,
+			"fd":               256,
+			"conns":            100,
+			"conns_inbound":    50,
+			"conns_outbound":   50,
+			"streams":          200,
+			"streams_inbound":  100,
+			"streams_outbound": 100,
+		},
+		"transient": {
+			"memory":           512 * 1024 * 1024,
+			"fd":               128,
+			"conns":            50,
+			"conns_inbound":    25,
+			"conns_outbound":   25,
+			"streams":          100,
+			"streams_inbound":  50,
+			"streams_outbound": 50,
+		},
+	}
+
+	for _, metric := range limitsMetric.GetMetric() {
+		var scope, resource string
+		for _, label := range metric.GetLabel() {
+			if label.GetName() == "scope" {
+				scope = label.GetValue()
+			}
+			if label.GetName() == "resource" {
+				resource = label.GetValue()
+			}
+		}
+
+		if scope == "" || resource == "" {
+			continue
+		}
+
+		expectedValue, ok := expectedLimits[scope][resource]
+		if !ok {
+			continue
+		}
+
+		actualValue := metric.GetGauge().GetValue()
+		if actualValue != expectedValue {
+			t.Errorf("limit mismatch for %s/%s: expected %v, got %v", scope, resource, expectedValue, actualValue)
+		}
+	}
+}
+
+func TestReportSystemLimitsNilLimiter(t *testing.T) {
+	reporter, err := NewStatsTraceReporter()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Should not panic with nil limiter
+	reporter.ReportSystemLimits(nil)
+}

p2p/host/resource-manager/rcmgr.go

@@ -178,17 +178,20 @@ func NewResourceManager(limits Limiter, opts ...Option) (network.ResourceManager
 	r.verifySourceAddressRateLimiter = newVerifySourceAddressRateLimiter(r.connLimiter)
 
 	if !r.disableMetrics {
-		var sr TraceReporter
 		sr, err := NewStatsTraceReporter()
 		if err != nil {
 			log.Error("failed to initialise StatsTraceReporter", "err", err)
 		} else {
+			// Report system limits to Prometheus
+			sr.ReportSystemLimits(limits)
+
 			if r.trace == nil {
 				r.trace = &trace{}
 			}
 			found := false
 			for _, rep := range r.trace.reporters {
-				if rep == sr {
+				// Compare the actual reporter, not the interface
+				if _, ok := rep.(StatsTraceReporter); ok {
 					found = true
 					break
 				}

p2p/host/resource-manager/stats.go

@@ -3,6 +3,7 @@ package rcmgr
 import (
 	"strings"
 
+	"github.com/libp2p/go-libp2p/core/network"
 	"github.com/libp2p/go-libp2p/p2p/metricshelper"
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -123,6 +124,13 @@ var (
 		Name:      "blocked_resources",
 		Help:      "Number of blocked resources",
 	}, []string{"dir", "scope", "resource"})
+
+	// System limits
+	limits = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: metricNamespace,
+		Name:      "limit",
+		Help:      "Resource manager limits",
+	}, []string{"scope", "resource"})
 )
 
 var (
@@ -157,6 +165,7 @@ func MustRegisterWith(reg prometheus.Registerer) {
 		previousConnMemory,
 		fds,
 		blockedResources,
+		limits,
 	)
 }
 
@@ -171,10 +180,47 @@ func WithMetricsDisabled() Option {
 type StatsTraceReporter struct{}
 
 func NewStatsTraceReporter() (StatsTraceReporter, error) {
-	// TODO tell prometheus the system limits
 	return StatsTraceReporter{}, nil
 }
 
+// reportLimit reports a limit value to Prometheus
+func reportLimit(scope, resource string, value int64) {
+	limits.With(prometheus.Labels{
+		"scope":    scope,
+		"resource": resource,
+	}).Set(float64(value))
+}
+
+// ReportSystemLimits reports the system limits to Prometheus.
+// This should be called after creating the StatsTraceReporter with the resource manager's limits.
+func (r StatsTraceReporter) ReportSystemLimits(limiter Limiter) {
+	if limiter == nil {
+		return
+	}
+
+	// System limits
+	systemLimits := limiter.GetSystemLimits()
+	reportLimit("system", "memory", systemLimits.GetMemoryLimit())
+	reportLimit("system", "fd", int64(systemLimits.GetFDLimit()))
+	reportLimit("system", "conns", int64(systemLimits.GetConnTotalLimit()))
+	reportLimit("system", "conns_inbound", int64(systemLimits.GetConnLimit(network.DirInbound)))
+	reportLimit("system", "conns_outbound", int64(systemLimits.GetConnLimit(network.DirOutbound)))
+	reportLimit("system", "streams", int64(systemLimits.GetStreamTotalLimit()))
+	reportLimit("system", "streams_inbound", int64(systemLimits.GetStreamLimit(network.DirInbound)))
+	reportLimit("system", "streams_outbound", int64(systemLimits.GetStreamLimit(network.DirOutbound)))
+
+	// Transient limits
+	transientLimits := limiter.GetTransientLimits()
+	reportLimit("transient", "memory", transientLimits.GetMemoryLimit())
+	reportLimit("transient", "fd", int64(transientLimits.GetFDLimit()))
+	reportLimit("transient", "conns", int64(transientLimits.GetConnTotalLimit()))
+	reportLimit("transient", "conns_inbound", int64(transientLimits.GetConnLimit(network.DirInbound)))
+	reportLimit("transient", "conns_outbound", int64(transientLimits.GetConnLimit(network.DirOutbound)))
+	reportLimit("transient", "streams", int64(transientLimits.GetStreamTotalLimit()))
+	reportLimit("transient", "streams_inbound", int64(transientLimits.GetStreamLimit(network.DirInbound)))
+	reportLimit("transient", "streams_outbound", int64(transientLimits.GetStreamLimit(network.DirOutbound)))
+}
+
 func (r StatsTraceReporter) ConsumeEvent(evt TraceEvt) {
 	tags := metricshelper.GetStringSlice()
 	defer metricshelper.PutStringSlice(tags)