feat: add prometheus metrics and dashboard

pkg/broker/broker.go

@@ -4,9 +4,11 @@ import (
 	"context"
 	"fmt"
 	"sync"
+	"time"
 
 	"git.warky.dev/wdevs/pgsql-broker/pkg/broker/adapter"
 	"git.warky.dev/wdevs/pgsql-broker/pkg/broker/config"
+	"git.warky.dev/wdevs/pgsql-broker/pkg/broker/metrics"
 )
 
 // Broker manages multiple database instances
@@ -17,6 +19,8 @@ type Broker struct {
 	instances []*DatabaseInstance
 	ctx       context.Context
 	cancel    context.CancelFunc
+	metrics   *metrics.Metrics
+	server    *metrics.Server
 	shutdown  bool
 	mu        sync.RWMutex
 }
@@ -33,6 +37,16 @@ func New(cfg *config.Config, logger adapter.Logger, version string) (*Broker, er
 		ctx:       ctx,
 		cancel:    cancel,
 	}
+	if cfg.Broker.MetricsEnabled {
+		broker.metrics = metrics.New()
+		broker.metrics.SetDatabaseCount(len(cfg.Databases))
+		addr := fmt.Sprintf("%s:%d", cfg.Broker.MetricsHost, cfg.Broker.MetricsPort)
+		server, err := metrics.NewServer(broker.metrics, addr, broker.logger)
+		if err != nil {
+			return nil, err
+		}
+		broker.server = server
+	}
 
 	return broker, nil
 }
@@ -50,7 +64,7 @@ func (b *Broker) Start() error {
 		dbAdapter := adapter.NewPostgresAdapter(dbCfg.ToPostgresConfig(), b.logger)
 
 		// Create database instance
-		instance, err := NewDatabaseInstance(b.config, dbCfg, dbAdapter, b.logger, b.version, b.ctx)
+		instance, err := NewDatabaseInstance(b.config, dbCfg, dbAdapter, b.logger, b.version, b.ctx, b.metrics)
 		if err != nil {
 			// Stop any already-started instances
 			b.stopInstances()
@@ -69,6 +83,9 @@ func (b *Broker) Start() error {
 	}
 
 	b.logger.Info("broker started successfully", "database_instances", len(b.instances))
+	if b.server != nil {
+		b.server.Start()
+	}
 	return nil
 }
 
@@ -89,6 +106,13 @@ func (b *Broker) Stop() error {
 
 	// Stop all instances
 	b.stopInstances()
+	if b.server != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := b.server.Stop(ctx); err != nil {
+			b.logger.Error("failed to stop metrics server", "error", err)
+		}
+	}
 
 	b.logger.Info("broker stopped")
 	return nil