feat: make prometheus registry configurable

Rather than implicitly use the default prometheus registry, we now
require the prometheus registry to be explicitly provided. This avoids
conflicts when used as a library, as well as providing more flexibility.

chainsync/chainsync.go

@@ -30,17 +30,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
-var (
-	blockNum_int = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cardano_node_metrics_blockNum_int",
-		Help: "current block number",
-	})
-	slotNum_int = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cardano_node_metrics_slotNum_int",
-		Help: "current slot number",
-	})
-)
-
 type ChainsyncClientState struct {
 	Cursor               ocommon.Point
 	ChainIter            *state.ChainIterator
@@ -53,14 +42,29 @@ type State struct {
 	ledgerState  *state.LedgerState
 	clients      map[ouroboros.ConnectionId]*ChainsyncClientState
 	clientConnId *ouroboros.ConnectionId // TODO: replace with handling of multiple chainsync clients
+	metrics      struct {
+		blockNum prometheus.Gauge
+		slotNum  prometheus.Gauge
+	}
 }
 
-func NewState(eventBus *event.EventBus, ledgerState *state.LedgerState) *State {
-	return &State{
+func NewState(eventBus *event.EventBus, ledgerState *state.LedgerState, promRegistry prometheus.Registerer) *State {
+	s := &State{
 		eventBus:    eventBus,
 		ledgerState: ledgerState,
 		clients:     make(map[ouroboros.ConnectionId]*ChainsyncClientState),
 	}
+	// Init metrics
+	promautoFactory := promauto.With(promRegistry)
+	s.metrics.blockNum = promautoFactory.NewGauge(prometheus.GaugeOpts{
+		Name: "cardano_node_metrics_blockNum_int",
+		Help: "current block number",
+	})
+	s.metrics.slotNum = promautoFactory.NewGauge(prometheus.GaugeOpts{
+		Name: "cardano_node_metrics_slotNum_int",
+		Help: "current slot number",
+	})
+	return s
 }
 
 func (s *State) AddClient(
@@ -116,8 +120,8 @@ func (s *State) AddBlock(block ledger.Block, blockType uint) error {
 	// block number isn't stored in the block itself
 	blockNumber := block.BlockNumber()
 	// Uodate metrics
-	blockNum_int.Set(float64(blockNumber))
-	slotNum_int.Set(float64(slotNumber))
+	s.metrics.blockNum.Set(float64(blockNumber))
+	s.metrics.slotNum.Set(float64(slotNumber))
 	// Generate event
 	blkHash, err := hex.DecodeString(block.Hash())
 	if err != nil {

config.go

@@ -21,6 +21,7 @@ import (
 
 	ouroboros "github.com/blinklabs-io/gouroboros"
 	ocommon "github.com/blinklabs-io/gouroboros/protocol/common"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 type Config struct {
@@ -31,8 +32,9 @@ type Config struct {
 	listeners          []ListenerConfig
 	network            string
 	networkMagic       uint32
-	peerSharing        bool
 	outboundSourcePort int
+	peerSharing        bool
+	promRegistry       prometheus.Registerer
 	topologyConfig     *TopologyConfig
 	tracing            bool
 	tracingStdout      bool
@@ -143,17 +145,25 @@ func WithNetworkMagic(networkMagic uint32) ConfigOptionFunc {
 	}
 }
 
+// WithOutboundSourcePort specifies the source port to use for outbound connections. This defaults to dynamic source ports
+func WithOutboundSourcePort(port int) ConfigOptionFunc {
+	return func(c *Config) {
+		c.outboundSourcePort = port
+	}
+}
+
 // WithPeerSharing specifies whether to enable peer sharing. This is disabled by default
 func WithPeerSharing(peerSharing bool) ConfigOptionFunc {
 	return func(c *Config) {
 		c.peerSharing = peerSharing
 	}
 }
 
-// WithOutboundSourcePort specifies the source port to use for outbound connections. This defaults to dynamic source ports
-func WithOutboundSourcePort(port int) ConfigOptionFunc {
+// WithPrometheusRegistry specifies a prometheus.Registerer instance to add metrics to. In most cases, prometheus.DefaultRegistry would be
+// a good choice to get metrics working
+func WithPrometheusRegistry(registry prometheus.Registerer) ConfigOptionFunc {
 	return func(c *Config) {
-		c.outboundSourcePort = port
+		c.promRegistry = registry
 	}
 }
 

event/event.go

@@ -17,6 +17,8 @@ package event
 import (
 	"sync"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 const (
@@ -47,13 +49,16 @@ type EventBus struct {
 	sync.Mutex
 	subscribers map[EventType]map[EventSubscriberId]chan Event
 	lastSubId   EventSubscriberId
+	metrics     eventMetrics
 }
 
 // NewEventBus creates a new EventBus
-func NewEventBus() *EventBus {
-	return &EventBus{
+func NewEventBus(promRegistry prometheus.Registerer) *EventBus {
+	e := &EventBus{
 		subscribers: make(map[EventType]map[EventSubscriberId]chan Event),
 	}
+	e.initMetrics(promRegistry)
+	return e
 }
 
 // Subscribe allows a consumer to receive events of a particular type via a channel
@@ -71,7 +76,7 @@ func (e *EventBus) Subscribe(eventType EventType) (EventSubscriberId, <-chan Eve
 	}
 	evtTypeSubs := e.subscribers[eventType]
 	evtTypeSubs[subId] = evtCh
-	metricSubscribers.WithLabelValues(string(eventType)).Inc()
+	e.metrics.subscribers.WithLabelValues(string(eventType)).Inc()
 	return subId, evtCh
 }
 
@@ -97,7 +102,7 @@ func (e *EventBus) Unsubscribe(eventType EventType, subId EventSubscriberId) {
 	if evtTypeSubs, ok := e.subscribers[eventType]; ok {
 		delete(evtTypeSubs, subId)
 	}
-	metricSubscribers.WithLabelValues(string(eventType)).Dec()
+	e.metrics.subscribers.WithLabelValues(string(eventType)).Dec()
 }
 
 // Publish allows a producer to send an event of a particular type to all subscribers
@@ -112,5 +117,5 @@ func (e *EventBus) Publish(eventType EventType, evt Event) {
 			subCh <- evt
 		}
 	}
-	metricEventsTotal.WithLabelValues(string(eventType)).Inc()
+	e.metrics.eventsTotal.WithLabelValues(string(eventType)).Inc()
 }

event/event_test.go

@@ -24,7 +24,7 @@ import (
 func TestEventBusSingleSubscriber(t *testing.T) {
 	var testEvtData int = 999
 	var testEvtType event.EventType = "test.event"
-	eb := event.NewEventBus()
+	eb := event.NewEventBus(nil)
 	_, subCh := eb.Subscribe(testEvtType)
 	eb.Publish(testEvtType, event.NewEvent(testEvtType, testEvtData))
 	select {
@@ -48,7 +48,7 @@ func TestEventBusSingleSubscriber(t *testing.T) {
 func TestEventBusMultipleSubscribers(t *testing.T) {
 	var testEvtData int = 999
 	var testEvtType event.EventType = "test.event"
-	eb := event.NewEventBus()
+	eb := event.NewEventBus(nil)
 	_, sub1Ch := eb.Subscribe(testEvtType)
 	_, sub2Ch := eb.Subscribe(testEvtType)
 	eb.Publish(testEvtType, event.NewEvent(testEvtType, testEvtData))
@@ -99,7 +99,7 @@ func TestEventBusMultipleSubscribers(t *testing.T) {
 func TestEventBusUnsubscribe(t *testing.T) {
 	var testEvtData int = 999
 	var testEvtType event.EventType = "test.event"
-	eb := event.NewEventBus()
+	eb := event.NewEventBus(nil)
 	subId, subCh := eb.Subscribe(testEvtType)
 	eb.Unsubscribe(testEvtType, subId)
 	eb.Publish(testEvtType, event.NewEvent(testEvtType, testEvtData))

event/metrics.go

@@ -19,19 +19,25 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
-var (
-	metricEventsTotal = promauto.NewCounterVec(
+type eventMetrics struct {
+	eventsTotal *prometheus.CounterVec
+	subscribers *prometheus.GaugeVec
+}
+
+func (e *EventBus) initMetrics(promRegistry prometheus.Registerer) {
+	promautoFactory := promauto.With(promRegistry)
+	e.metrics.eventsTotal = promautoFactory.NewCounterVec(
 		prometheus.CounterOpts{
 			Name: "event_total",
 			Help: "total events by type",
 		},
 		[]string{"type"},
 	)
-	metricSubscribers = promauto.NewGaugeVec(
+	e.metrics.subscribers = promautoFactory.NewGaugeVec(
 		prometheus.GaugeOpts{
 			Name: "event_subscribers",
 			Help: "subscribers by event type",
 		},
 		[]string{"type"},
 	)
-)
+}

internal/node/node.go

@@ -18,8 +18,13 @@ import (
 	"fmt"
 	"log/slog"
 	"net"
+	"net/http"
+	"os"
 
 	"github.com/blinklabs-io/node"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 func Run(logger *slog.Logger) error {
@@ -29,6 +34,16 @@ func Run(logger *slog.Logger) error {
 		return err
 	}
 	logger.Info("listening for ouroboros node-to-node connections on :3001")
+	// Metrics listener
+	http.Handle("/metrics", promhttp.Handler())
+	logger.Info("listening for prometheus metrics connections on :12798")
+	go func() {
+		// TODO: make this configurable
+		if err := http.ListenAndServe(":12798", nil); err != nil {
+			logger.Error(fmt.Sprintf("failed to start metrics listener: %s", err))
+			os.Exit(1)
+		}
+	}()
 	n, err := node.New(
 		node.NewConfig(
 			node.WithIntersectTip(true),
@@ -42,6 +57,8 @@ func Run(logger *slog.Logger) error {
 					Listener: l,
 				},
 			),
+			// Enable metrics with default prometheus registry
+			node.WithPrometheusRegistry(prometheus.DefaultRegisterer),
 			// TODO: make this configurable
 			//node.WithTracing(true),
 			// TODO: replace with parsing topology file
@@ -64,11 +81,6 @@ func Run(logger *slog.Logger) error {
 	if err != nil {
 		return err
 	}
-	go func() {
-		if err := n.StartMetrics(); err != nil {
-			logger.Error(fmt.Sprintf("failed to start metrics listener %v", err))
-		}
-	}()
 	if err := n.Run(); err != nil {
 		return err
 	}

mempool/mempool.go

@@ -49,21 +49,6 @@ type RemoveTransactionEvent struct {
 	Hash string
 }
 
-var (
-	txsProcessedNum_int = promauto.NewCounter(prometheus.CounterOpts{
-		Name: "cardano_node_metrics_txsProcessedNum_int",
-		Help: "total transactions processed",
-	})
-	txsInMempool_int = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cardano_node_metrics_txsInMempool_int",
-		Help: "current count of mempool transactions",
-	})
-	mempoolBytes_int = promauto.NewGauge(prometheus.GaugeOpts{
-		Name: "cardano_node_metrics_mempoolBytes_int",
-		Help: "current size of mempool transactions in bytes",
-	})
-)
-
 type MempoolTransaction struct {
 	Hash     string
 	Type     uint
@@ -80,9 +65,14 @@ type Mempool struct {
 	consumerIndex      map[ouroboros.ConnectionId]int
 	consumerIndexMutex sync.Mutex
 	transactions       []*MempoolTransaction
+	metrics            struct {
+		txsProcessedNum prometheus.Counter
+		txsInMempool    prometheus.Gauge
+		mempoolBytes    prometheus.Gauge
+	}
 }
 
-func NewMempool(logger *slog.Logger, eventBus *event.EventBus) *Mempool {
+func NewMempool(logger *slog.Logger, eventBus *event.EventBus, promRegistry prometheus.Registerer) *Mempool {
 	m := &Mempool{
 		eventBus:  eventBus,
 		consumers: make(map[ouroboros.ConnectionId]*MempoolConsumer),
@@ -95,6 +85,20 @@ func NewMempool(logger *slog.Logger, eventBus *event.EventBus) *Mempool {
 	// TODO: replace this with purging based on on-chain TXs
 	// Schedule initial mempool expired cleanup
 	m.scheduleRemoveExpired()
+	// Init metrics
+	promautoFactory := promauto.With(promRegistry)
+	m.metrics.txsProcessedNum = promautoFactory.NewCounter(prometheus.CounterOpts{
+		Name: "cardano_node_metrics_txsProcessedNum_int",
+		Help: "total transactions processed",
+	})
+	m.metrics.txsInMempool = promautoFactory.NewGauge(prometheus.GaugeOpts{
+		Name: "cardano_node_metrics_txsInMempool_int",
+		Help: "current count of mempool transactions",
+	})
+	m.metrics.mempoolBytes = promautoFactory.NewGauge(prometheus.GaugeOpts{
+		Name: "cardano_node_metrics_mempoolBytes_int",
+		Help: "current size of mempool transactions in bytes",
+	})
 	return m
 }
 
@@ -201,9 +205,9 @@ func (m *Mempool) AddTransaction(tx MempoolTransaction) error {
 	m.logger.Debug(
 		fmt.Sprintf("added transaction %s to mempool", tx.Hash),
 	)
-	txsProcessedNum_int.Inc()
-	txsInMempool_int.Inc()
-	mempoolBytes_int.Add(float64(len(tx.Cbor)))
+	m.metrics.txsProcessedNum.Inc()
+	m.metrics.txsInMempool.Inc()
+	m.metrics.mempoolBytes.Add(float64(len(tx.Cbor)))
 	// Send new TX to consumers that are ready for it
 	newTxIdx := len(m.transactions) - 1
 	for connId, consumerIdx := range m.consumerIndex {
@@ -268,8 +272,8 @@ func (m *Mempool) removeTransaction(hash string) bool {
 				txIdx,
 				txIdx+1,
 			)
-			txsInMempool_int.Dec()
-			mempoolBytes_int.Sub(float64(len(tx.Cbor)))
+			m.metrics.txsInMempool.Dec()
+			m.metrics.mempoolBytes.Sub(float64(len(tx.Cbor)))
 			// Update consumer indexes to reflect removed TX
 			for connId, consumerIdx := range m.consumerIndex {
 				// Decrement consumer index if the consumer has reached the removed TX