Code sanity fixes, added middlewares

pkg/metrics/prometheus.go

@@ -0,0 +1,174 @@
+package metrics
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// PrometheusProvider implements the Provider interface using Prometheus
+type PrometheusProvider struct {
+	requestDuration   *prometheus.HistogramVec
+	requestTotal      *prometheus.CounterVec
+	requestsInFlight  prometheus.Gauge
+	dbQueryDuration   *prometheus.HistogramVec
+	dbQueryTotal      *prometheus.CounterVec
+	cacheHits         *prometheus.CounterVec
+	cacheMisses       *prometheus.CounterVec
+	cacheSize         *prometheus.GaugeVec
+}
+
+// NewPrometheusProvider creates a new Prometheus metrics provider
+func NewPrometheusProvider() *PrometheusProvider {
+	return &PrometheusProvider{
+		requestDuration: promauto.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:    "http_request_duration_seconds",
+				Help:    "HTTP request duration in seconds",
+				Buckets: prometheus.DefBuckets,
+			},
+			[]string{"method", "path", "status"},
+		),
+		requestTotal: promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "http_requests_total",
+				Help: "Total number of HTTP requests",
+			},
+			[]string{"method", "path", "status"},
+		),
+
+		requestsInFlight: promauto.NewGauge(
+			prometheus.GaugeOpts{
+				Name: "http_requests_in_flight",
+				Help: "Current number of HTTP requests being processed",
+			},
+		),
+		dbQueryDuration: promauto.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:    "db_query_duration_seconds",
+				Help:    "Database query duration in seconds",
+				Buckets: prometheus.DefBuckets,
+			},
+			[]string{"operation", "table"},
+		),
+		dbQueryTotal: promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "db_queries_total",
+				Help: "Total number of database queries",
+			},
+			[]string{"operation", "table", "status"},
+		),
+		cacheHits: promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "cache_hits_total",
+				Help: "Total number of cache hits",
+			},
+			[]string{"provider"},
+		),
+		cacheMisses: promauto.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "cache_misses_total",
+				Help: "Total number of cache misses",
+			},
+			[]string{"provider"},
+		),
+		cacheSize: promauto.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "cache_size_items",
+				Help: "Number of items in cache",
+			},
+			[]string{"provider"},
+		),
+	}
+}
+
+// ResponseWriter wraps http.ResponseWriter to capture status code
+type ResponseWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func NewResponseWriter(w http.ResponseWriter) *ResponseWriter {
+	return &ResponseWriter{
+		ResponseWriter: w,
+		statusCode:     http.StatusOK,
+	}
+}
+
+func (rw *ResponseWriter) WriteHeader(code int) {
+	rw.statusCode = code
+	rw.ResponseWriter.WriteHeader(code)
+}
+
+// RecordHTTPRequest implements Provider interface
+func (p *PrometheusProvider) RecordHTTPRequest(method, path, status string, duration time.Duration) {
+	p.requestDuration.WithLabelValues(method, path, status).Observe(duration.Seconds())
+	p.requestTotal.WithLabelValues(method, path, status).Inc()
+}
+
+// IncRequestsInFlight implements Provider interface
+func (p *PrometheusProvider) IncRequestsInFlight() {
+	p.requestsInFlight.Inc()
+}
+
+// DecRequestsInFlight implements Provider interface
+func (p *PrometheusProvider) DecRequestsInFlight() {
+	p.requestsInFlight.Dec()
+}
+
+// RecordDBQuery implements Provider interface
+func (p *PrometheusProvider) RecordDBQuery(operation, table string, duration time.Duration, err error) {
+	status := "success"
+	if err != nil {
+		status = "error"
+	}
+	p.dbQueryDuration.WithLabelValues(operation, table).Observe(duration.Seconds())
+	p.dbQueryTotal.WithLabelValues(operation, table, status).Inc()
+}
+
+// RecordCacheHit implements Provider interface
+func (p *PrometheusProvider) RecordCacheHit(provider string) {
+	p.cacheHits.WithLabelValues(provider).Inc()
+}
+
+// RecordCacheMiss implements Provider interface
+func (p *PrometheusProvider) RecordCacheMiss(provider string) {
+	p.cacheMisses.WithLabelValues(provider).Inc()
+}
+
+// UpdateCacheSize implements Provider interface
+func (p *PrometheusProvider) UpdateCacheSize(provider string, size int64) {
+	p.cacheSize.WithLabelValues(provider).Set(float64(size))
+}
+
+// Handler implements Provider interface
+func (p *PrometheusProvider) Handler() http.Handler {
+	return promhttp.Handler()
+}
+
+// Middleware returns an HTTP middleware that collects metrics
+func (p *PrometheusProvider) Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+
+		// Increment in-flight requests
+		p.IncRequestsInFlight()
+		defer p.DecRequestsInFlight()
+
+		// Wrap response writer to capture status code
+		rw := NewResponseWriter(w)
+
+		// Call next handler
+		next.ServeHTTP(rw, r)
+
+		// Record metrics
+		duration := time.Since(start)
+		status := strconv.Itoa(rw.statusCode)
+
+		p.RecordHTTPRequest(r.Method, r.URL.Path, status, duration)
+	})
+}