Add Prometheus metrics endpoint; containerize integration tests

Prometheus metrics (internal/metrics/, cmd/maglevd/)
- New --metrics-addr flag (default :9091, env MAGLEV_METRICS_ADDR)
  serving /metrics via promhttp.
- Gauge metrics scraped on demand via a custom prometheus.Collector:
  maglev_backend_state, maglev_backend_health, maglev_backend_enabled,
  maglev_frontend_pool_backend_weight.
- Inline counter/histogram metrics updated per probe:
  maglev_probe_total (by backend, type, result, code),
  maglev_probe_duration_seconds (by backend, type),
  maglev_backend_transitions_total (by backend, from, to).
- StateSource interface in metrics package breaks the import cycle
  with checker; checker.Checker satisfies it via GetBackendInfo.

Integration tests
- Run maglevd inside a containerlab node (debian:trixie-slim with
  build/ bind-mounted) instead of on the host. Eliminates port
  collisions with any host maglevd.
- maglevc commands run via docker exec into the maglevd container.
- Add 6 Prometheus test cases: endpoint reachable, all backends
  report state=up, probe counters non-zero, duration histogram
  populated, pool weights correct, transition counters present.

cmd/maglevd/main.go

@@ -8,10 +8,13 @@ import (
 	"fmt"
 	"log/slog"
 	"net"
+	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
 
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/reflection"
 
@@ -19,6 +22,7 @@ import (
 	"git.ipng.ch/ipng/vpp-maglev/internal/checker"
 	"git.ipng.ch/ipng/vpp-maglev/internal/config"
 	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
+	"git.ipng.ch/ipng/vpp-maglev/internal/metrics"
 )
 
 func main() {
@@ -35,6 +39,7 @@ func run() error {
 	enableReflection := flag.Bool("reflection", true, "enable gRPC server reflection (for grpcurl)")
 	configPath := stringFlag("config", "/etc/vpp-maglev/maglev.yaml", "MAGLEV_CONFIG", "path to maglev.yaml")
 	grpcAddr := stringFlag("grpc-addr", ":9090", "MAGLEV_GRPC_ADDR", "gRPC listen address")
+	metricsAddr := stringFlag("metrics-addr", ":9091", "MAGLEV_METRICS_ADDR", "Prometheus /metrics listen address (empty to disable)")
 	logLevel := stringFlag("log-level", "info", "MAGLEV_LOG_LEVEL", "log level (debug|info|warn|error)")
 	flag.Parse()
 
@@ -106,6 +111,21 @@ func run() error {
 		}
 	}()
 
+	// ---- Prometheus metrics -------------------------------------------------
+	if *metricsAddr != "" {
+		reg := prometheus.DefaultRegisterer
+		metrics.Register(reg, chkr)
+
+		mux := http.NewServeMux()
+		mux.Handle("/metrics", promhttp.Handler())
+		slog.Info("metrics-listening", "addr", *metricsAddr)
+		go func() {
+			if err := http.ListenAndServe(*metricsAddr, mux); err != nil && err != http.ErrServerClosed {
+				slog.Error("metrics-serve-error", "err", err)
+			}
+		}()
+	}
+
 	// ---- signal handling ----------------------------------------------------
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, syscall.SIGHUP, syscall.SIGTERM, syscall.SIGINT)

docs/user-guide.md

@@ -12,6 +12,7 @@ inspection and control.
 |---|---|---|---|
 | `--config` | `MAGLEV_CONFIG` | `/etc/vpp-maglev/maglev.yaml` | Path to the YAML configuration file. |
 | `--grpc-addr` | `MAGLEV_GRPC_ADDR` | `:9090` | TCP address on which the gRPC server listens. |
+| `--metrics-addr` | `MAGLEV_METRICS_ADDR` | `:9091` | TCP address for the Prometheus `/metrics` HTTP endpoint. Set to empty to disable. |
 | `--log-level` | `MAGLEV_LOG_LEVEL` | `info` | Log verbosity: `debug`, `info`, `warn`, or `error`. |
 | `--check` | — | — | Read and validate the config file, then exit. Exits 0 if the config is valid, 1 on YAML parse error, 2 on semantic error. |
 | `--reflection` | — | `true` | Enable gRPC server reflection. Allows `grpcurl` to introspect the API without the `.proto` file. Set to `false` to disable. |

go.mod

@@ -13,6 +13,14 @@ require (
 )
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_golang v1.23.2 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/common v0.66.1 // indirect
+	github.com/prometheus/procfs v0.16.1 // indirect
+	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	golang.org/x/text v0.35.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260120221211-b8f7ae30c516 // indirect
 )

go.sum

@@ -1,3 +1,5 @@
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/chzyer/logex v1.2.1 h1:XHDu3E6q+gdHgsdTPH6ImJMIp436vR6MPtH8gP05QzM=
@@ -16,6 +18,16 @@ github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h0RJWRi/o0o=
+github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
+github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
+github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
+github.com/prometheus/common v0.66.1 h1:h5E0h5/Y8niHc5DlaLlWLArTQI7tMrsfQjHV+d9ZoGs=
+github.com/prometheus/common v0.66.1/go.mod h1:gcaUsgf3KfRSwHY4dIMXLPV0K/Wg1oZ8+SbZk/HH/dA=
+github.com/prometheus/procfs v0.16.1 h1:hZ15bTNuirocR6u0JZ6BAHHmwS1p8B4P6MRqxtzMyRg=
+github.com/prometheus/procfs v0.16.1/go.mod h1:teAbpZRB1iIAJYREa1LsoWUXykVXA1KlTmWl8x/U+Is=
 github.com/vishvananda/netns v0.0.5 h1:DfiHV+j8bA32MFM7bfEunvT8IAqQ/NzSJHtcmW5zdEY=
 github.com/vishvananda/netns v0.0.5/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
@@ -30,6 +42,8 @@ go.opentelemetry.io/otel/sdk/metric v1.39.0 h1:cXMVVFVgsIf2YL6QkRF4Urbr/aMInf+2W
 go.opentelemetry.io/otel/sdk/metric v1.39.0/go.mod h1:xq9HEVH7qeX69/JnwEfp6fVq5wosJsY1mt4lLfYdVew=
 go.opentelemetry.io/otel/trace v1.39.0 h1:2d2vfpEDmCJ5zVYz7ijaJdOF59xLomrvj7bjt6/qCJI=
 go.opentelemetry.io/otel/trace v1.39.0/go.mod h1:88w4/PnZSazkGzz/w84VHpQafiU4EtqqlVdxWy+rNOA=
+go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
+go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
 golang.org/x/net v0.52.0 h1:He/TN1l0e4mmR3QqHMT2Xab3Aj3L9qjbhRm78/6jrW0=
 golang.org/x/net v0.52.0/go.mod h1:R1MAz7uMZxVMualyPXb+VaqGSa3LIaUqk0eEt3w36Sw=
 golang.org/x/sys v0.0.0-20220310020820-b874c991c1a5/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

internal/checker/checker.go

@@ -13,6 +13,7 @@ import (
 
 	"git.ipng.ch/ipng/vpp-maglev/internal/config"
 	"git.ipng.ch/ipng/vpp-maglev/internal/health"
+	"git.ipng.ch/ipng/vpp-maglev/internal/metrics"
 	"git.ipng.ch/ipng/vpp-maglev/internal/prober"
 )
 
@@ -267,6 +268,22 @@ func (c *Checker) GetBackend(name string) (BackendSnapshot, bool) {
 	return BackendSnapshot{Health: w.backend, Config: w.entry}, true
 }
 
+// GetBackendInfo returns the health state and key config fields for a backend.
+// Satisfies metrics.StateSource.
+func (c *Checker) GetBackendInfo(name string) (metrics.BackendInfo, bool) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	w, ok := c.workers[name]
+	if !ok {
+		return metrics.BackendInfo{}, false
+	}
+	return metrics.BackendInfo{
+		Health:  w.backend,
+		Enabled: w.entry.Enabled,
+		HCName:  w.entry.HealthCheck,
+	}, true
+}
+
 // PauseBackend pauses health checking for a backend by name. The probe
 // goroutine is cancelled so no further traffic is sent to the backend. The
 // backend's state is set to paused and remains frozen until ResumeBackend is
@@ -466,6 +483,7 @@ func (c *Checker) runProbe(ctx context.Context, name string, pos, total int) {
 			slog.Debug("probe-start", "backend", name, "type", hc.Type)
 			start := time.Now()
 			result = prober.ForType(hc.Type)(probeCtx, pcfg)
+			elapsed := time.Since(start)
 			cancel()
 			slog.Debug("probe-done",
 				"backend", name,
@@ -473,8 +491,14 @@ func (c *Checker) runProbe(ctx context.Context, name string, pos, total int) {
 				"ok", result.OK,
 				"code", result.Code,
 				"detail", result.Detail,
-				"elapsed", time.Since(start).Round(time.Millisecond).String(),
+				"elapsed", elapsed.Round(time.Millisecond).String(),
 			)
+			res := "success"
+			if !result.OK {
+				res = "failure"
+			}
+			metrics.ProbeTotal.WithLabelValues(name, hc.Type, res, result.Code).Inc()
+			metrics.ProbeDuration.WithLabelValues(name, hc.Type).Observe(elapsed.Seconds())
 		}
 
 		c.mu.Lock()
@@ -493,6 +517,7 @@ func (c *Checker) runProbe(ctx context.Context, name string, pos, total int) {
 				"code", result.Code,
 				"detail", result.Detail,
 			)
+			metrics.TransitionTotal.WithLabelValues(name, t.From.String(), t.To.String()).Inc()
 			c.emitForBackend(name, addr, t, c.cfg.Frontends)
 		}
 		c.mu.Unlock()

internal/metrics/metrics.go

@@ -0,0 +1,176 @@
+// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>
+
+// Package metrics exposes Prometheus metrics for maglevd.
+//
+// Gauge-type metrics (backend state, health counter, weights) are collected
+// on demand when Prometheus scrapes /metrics via the Collector. Counter and
+// histogram metrics (probe totals, probe duration, transitions) are updated
+// inline from the probe loop.
+package metrics
+
+import (
+	"git.ipng.ch/ipng/vpp-maglev/internal/config"
+	"git.ipng.ch/ipng/vpp-maglev/internal/health"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// BackendInfo holds the health and config state needed by the collector.
+type BackendInfo struct {
+	Health  *health.Backend
+	Enabled bool
+	HCName  string // healthcheck name from config
+}
+
+// StateSource provides read-only access to the running checker state.
+type StateSource interface {
+	ListBackends() []string
+	GetBackendInfo(name string) (BackendInfo, bool)
+	ListFrontends() []string
+	GetFrontend(name string) (config.Frontend, bool)
+}
+
+// ---- inline metrics (updated per probe) ------------------------------------
+
+var (
+	ProbeTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "maglev",
+		Subsystem: "probe",
+		Name:      "total",
+		Help:      "Total number of health-check probes executed.",
+	}, []string{"backend", "type", "result", "code"})
+
+	ProbeDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "maglev",
+		Subsystem: "probe",
+		Name:      "duration_seconds",
+		Help:      "Health-check probe duration in seconds.",
+		Buckets:   []float64{.001, .0025, .005, .01, .025, .05, .1, .25, .5, 1, 2.5},
+	}, []string{"backend", "type"})
+
+	TransitionTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "maglev",
+		Subsystem: "backend",
+		Name:      "transitions_total",
+		Help:      "Total number of backend state transitions.",
+	}, []string{"backend", "from", "to"})
+)
+
+// ---- collector (scraped on demand) -----------------------------------------
+
+// Collector implements prometheus.Collector by querying the running checker
+// on each scrape. This avoids stale label sets when backends are added or
+// removed by a config reload.
+type Collector struct {
+	src StateSource
+
+	backendState   *prometheus.Desc
+	backendHealth  *prometheus.Desc
+	backendEnabled *prometheus.Desc
+	poolWeight     *prometheus.Desc
+}
+
+// NewCollector creates a Collector backed by the given StateSource.
+func NewCollector(src StateSource) *Collector {
+	return &Collector{
+		src: src,
+		backendState: prometheus.NewDesc(
+			"maglev_backend_state",
+			"Current backend state (1 = active for the given state label).",
+			[]string{"backend", "address", "healthcheck", "state"}, nil,
+		),
+		backendHealth: prometheus.NewDesc(
+			"maglev_backend_health",
+			"Current health counter value.",
+			[]string{"backend"}, nil,
+		),
+		backendEnabled: prometheus.NewDesc(
+			"maglev_backend_enabled",
+			"Whether the backend is enabled (1) or disabled (0).",
+			[]string{"backend"}, nil,
+		),
+		poolWeight: prometheus.NewDesc(
+			"maglev_frontend_pool_backend_weight",
+			"Configured weight of a backend in a frontend pool (0-100).",
+			[]string{"frontend", "pool", "backend"}, nil,
+		),
+	}
+}
+
+// Describe implements prometheus.Collector.
+func (c *Collector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- c.backendState
+	ch <- c.backendHealth
+	ch <- c.backendEnabled
+	ch <- c.poolWeight
+}
+
+// Collect implements prometheus.Collector.
+func (c *Collector) Collect(ch chan<- prometheus.Metric) {
+	states := []health.State{
+		health.StateUnknown,
+		health.StateUp,
+		health.StateDown,
+		health.StatePaused,
+		health.StateRemoved,
+	}
+
+	for _, name := range c.src.ListBackends() {
+		info, ok := c.src.GetBackendInfo(name)
+		if !ok {
+			continue
+		}
+		addr := info.Health.Address.String()
+
+		// One time-series per possible state; the current state is 1, rest 0.
+		for _, s := range states {
+			val := 0.0
+			if info.Health.State == s {
+				val = 1.0
+			}
+			ch <- prometheus.MustNewConstMetric(
+				c.backendState, prometheus.GaugeValue, val,
+				name, addr, info.HCName, s.String(),
+			)
+		}
+
+		ch <- prometheus.MustNewConstMetric(
+			c.backendHealth, prometheus.GaugeValue,
+			float64(info.Health.Counter.Health), name,
+		)
+
+		enabled := 0.0
+		if info.Enabled {
+			enabled = 1.0
+		}
+		ch <- prometheus.MustNewConstMetric(
+			c.backendEnabled, prometheus.GaugeValue, enabled, name,
+		)
+	}
+
+	for _, feName := range c.src.ListFrontends() {
+		fe, ok := c.src.GetFrontend(feName)
+		if !ok {
+			continue
+		}
+		for _, pool := range fe.Pools {
+			for beName, pb := range pool.Backends {
+				ch <- prometheus.MustNewConstMetric(
+					c.poolWeight, prometheus.GaugeValue,
+					float64(pb.Weight), feName, pool.Name, beName,
+				)
+			}
+		}
+	}
+}
+
+// Register registers all metrics with the given registry.
+func Register(reg prometheus.Registerer, src StateSource) *Collector {
+	coll := NewCollector(src)
+	reg.MustRegister(coll)
+	reg.MustRegister(ProbeTotal)
+	reg.MustRegister(ProbeDuration)
+	reg.MustRegister(TransitionTotal)
+	return coll
+}
+

tests/01-maglevd/01-healthcheck.robot

@@ -1,6 +1,5 @@
 *** Settings ***
 Library             OperatingSystem
-Library             Process
 Resource            ../common.robot
 
 Suite Setup         Setup Suite
@@ -10,26 +9,20 @@ Suite Teardown      Cleanup Suite
 *** Variables ***
 ${lab-name}         maglevd-test
 ${lab-file}         maglevd-lab/maglevd.clab.yml
-${config-file}      maglevd-lab/maglev.yaml
 ${runtime}          docker
-${GRPC_PORT}        9091
+${MAGLEVD_NODE}     clab-maglevd-test-maglevd
+${METRICS_URL}      http://172.20.30.2:9091/metrics
 
 
 *** Test Cases ***
 Deploy maglevd-test lab
+    [Documentation]    Deploy the containerlab topology. The maglevd node starts
+    ...    automatically as PID 1 via start.sh and begins probing the nginx
+    ...    backends immediately.
     ${rc}    ${output} =    Run And Return Rc And Output
     ...    ${CLAB_BIN} --runtime ${runtime} deploy -t ${CURDIR}/${lab-file}
     Log    ${output}
     Should Be Equal As Integers    ${rc}    0
-
-Start maglevd
-    ${handle} =    Start Process    ${MAGLEVD}
-    ...    --config    ${CURDIR}/${config-file}
-    ...    --grpc-addr    :${GRPC_PORT}
-    ...    --log-level    debug
-    ...    alias=maglevd    stdout=${EXECDIR}/tests/out/maglevd.log
-    ...    stderr=STDOUT
-    Set Suite Variable    ${MAGLEVD_HANDLE}    ${handle}
     Sleep    3s    Wait for nginx containers and probes to converge
 
 All backends reach up state
@@ -86,22 +79,55 @@ Enable backend restarts probing
     ...    Backend Should Be Up    nginx2
 
 
+Prometheus endpoint is reachable
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    curl -sf ${METRICS_URL}
+    Log    ${output}
+    Should Be Equal As Integers    ${rc}    0
+    Should Contain    ${output}    maglev_backend_state
+
+Prometheus reports all backends up
+    ${output} =    Scrape Metrics
+    # Each backend should have state="up" = 1.
+    Should Contain    ${output}    maglev_backend_state{address="172.20.30.11",backend="nginx1",healthcheck="http-check",state="up"} 1
+    Should Contain    ${output}    maglev_backend_state{address="172.20.30.12",backend="nginx2",healthcheck="http-check",state="up"} 1
+    Should Contain    ${output}    maglev_backend_state{address="172.20.30.13",backend="nginx3",healthcheck="http-check",state="up"} 1
+
+Prometheus reports probe counters
+    ${output} =    Scrape Metrics
+    Should Match Regexp    ${output}    maglev_probe_total\\{backend="nginx1".*result="success".*\\}\\s+[1-9]
+    Should Match Regexp    ${output}    maglev_probe_total\\{backend="nginx2".*result="success".*\\}\\s+[1-9]
+    Should Match Regexp    ${output}    maglev_probe_total\\{backend="nginx3".*result="success".*\\}\\s+[1-9]
+
+Prometheus reports probe duration histogram
+    ${output} =    Scrape Metrics
+    Should Match Regexp    ${output}    maglev_probe_duration_seconds_count\\{backend="nginx1".*\\}\\s+[1-9]
+
+Prometheus reports pool weights
+    ${output} =    Scrape Metrics
+    Should Contain    ${output}    maglev_frontend_pool_backend_weight{backend="nginx1",frontend="http-vip",pool="primary"} 100
+    Should Contain    ${output}    maglev_frontend_pool_backend_weight{backend="nginx3",frontend="http-vip",pool="fallback"} 100
+
+Prometheus reports transition counters
+    ${output} =    Scrape Metrics
+    # All backends transitioned unknown → up during startup.
+    Should Match Regexp    ${output}    maglev_backend_transitions_total\\{backend="nginx1",from="unknown",to="up"\\}\\s+[1-9]
+
+
 *** Keywords ***
 Setup Suite
     ${arch} =    Run    go env GOARCH
     Set Suite Variable    ${ARCH}    ${arch}
-    Set Suite Variable    ${MAGLEVD}    ${EXECDIR}/build/${ARCH}/maglevd
-    Set Suite Variable    ${MAGLEVC}    ${EXECDIR}/build/${ARCH}/maglevc
 
 Cleanup Suite
-    Run Keyword And Ignore Error    Terminate Process    maglevd    kill=true
+    Run    docker logs ${MAGLEVD_NODE} > ${EXECDIR}/tests/out/maglevd.log 2>&1
     Run    ${CLAB_BIN} --runtime ${runtime} destroy -t ${CURDIR}/${lab-file} --cleanup
 
 Maglevc
-    [Documentation]    Run a maglevc command and return its output.
+    [Documentation]    Run a maglevc command inside the maglevd container.
     [Arguments]    ${cmd}
     ${rc}    ${output} =    Run And Return Rc And Output
-    ...    ${MAGLEVC} --server\=localhost:${GRPC_PORT} --color\=false ${cmd}
+    ...    docker exec ${MAGLEVD_NODE} /opt/maglev/build/${ARCH}/maglevc --color\=false ${cmd}
     Log    ${output}
     Should Be Equal As Integers    ${rc}    0
     RETURN    ${output}
@@ -133,3 +159,10 @@ Probe Count Should Be Positive
     ${count} =    Get Probe Count    ${name}
     Should Be True    ${count} > 0
     ...    No health-check requests found in nginx logs for ${name}
+
+Scrape Metrics
+    [Documentation]    Fetch the Prometheus /metrics endpoint from the maglevd container.
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    curl -sf ${METRICS_URL}
+    Should Be Equal As Integers    ${rc}    0
+    RETURN    ${output}

tests/01-maglevd/maglevd-lab/maglevd.clab.yml

@@ -6,6 +6,15 @@ mgmt:
 
 topology:
   nodes:
+    maglevd:
+      kind: linux
+      image: debian:trixie-slim
+      mgmt-ipv4: 172.20.30.2
+      binds:
+        - ../../../build:/opt/maglev/build:ro
+        - ./maglev.yaml:/etc/maglev/maglev.yaml:ro
+        - ./start.sh:/start.sh:ro
+      cmd: /start.sh
     nginx1:
       kind: linux
       image: nginx:alpine

tests/01-maglevd/maglevd-lab/start.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+ARCH=$(uname -m)
+case "$ARCH" in
+    x86_64)  ARCH=amd64 ;;
+    aarch64) ARCH=arm64 ;;
+esac
+exec /opt/maglev/build/${ARCH}/maglevd --config /etc/maglev/maglev.yaml --log-level debug