Changeset 0.33.0 (#207)

Co-authored-by: Jeffrey Smith <jasafpro@gmail.com>
Co-committed-by: Jeffrey Smith <jasafpro@gmail.com>

server/middleware/prometheus.go

@@ -0,0 +1,30 @@
+package middleware
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"chat-switchboard/metrics"
+)
+
+// Prometheus returns a Gin middleware that records HTTP request metrics.
+// Uses c.FullPath() (Gin's registered route pattern, e.g.
+// "/api/v1/channels/:id") to avoid label cardinality explosion from
+// path parameters.
+func Prometheus() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		start := time.Now()
+		c.Next()
+
+		pattern := c.FullPath()
+		if pattern == "" {
+			pattern = "unmatched"
+		}
+		status := strconv.Itoa(c.Writer.Status())
+
+		metrics.HTTPRequestsTotal.WithLabelValues(c.Request.Method, pattern, status).Inc()
+		metrics.HTTPRequestDuration.WithLabelValues(c.Request.Method, pattern).Observe(time.Since(start).Seconds())
+	}
+}