phase 10

internal/metrics/metrics.go

@@ -0,0 +1,82 @@
+// Package metrics provides in-process Prometheus-format instrumentation.
+// All counters and gauges use atomic operations and are safe for concurrent use.
+package metrics
+
+import (
+	"fmt"
+	"net/http"
+	"sync/atomic"
+	"time"
+)
+
+var startTime = time.Now()
+
+// Counters and gauges — updated by callers in ws.go and api.go.
+var (
+	wsConns       atomic.Int64 // current open WebSocket connections (gauge)
+	msgIn         atomic.Int64 // total WS messages received (counter)
+	msgOut        atomic.Int64 // total WS messages sent (counter)
+	writeOps      atomic.Int64 // total signal write operations (counter)
+	historyReqs   atomic.Int64 // total history requests served (counter)
+)
+
+// IncWsConns increments the active WebSocket connection gauge.
+func IncWsConns() { wsConns.Add(1) }
+
+// DecWsConns decrements the active WebSocket connection gauge.
+func DecWsConns() { wsConns.Add(-1) }
+
+// IncMsgIn increments the total inbound WS message counter.
+func IncMsgIn() { msgIn.Add(1) }
+
+// IncMsgOut increments the total outbound WS message counter.
+func IncMsgOut() { msgOut.Add(1) }
+
+// IncWrites increments the signal write operation counter.
+func IncWrites() { writeOps.Add(1) }
+
+// IncHistoryReqs increments the history request counter.
+func IncHistoryReqs() { historyReqs.Add(1) }
+
+// Handler returns an http.HandlerFunc that renders Prometheus-format metrics.
+// activeSubs is called each request to read the current number of unique signal
+// subscriptions from the broker; pass nil to omit the metric.
+func Handler(activeSubs func() int) http.HandlerFunc {
+	return func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
+
+		uptime := time.Since(startTime).Seconds()
+		subs := 0
+		if activeSubs != nil {
+			subs = activeSubs()
+		}
+
+		fmt.Fprintf(w, "# HELP uopi_uptime_seconds Seconds elapsed since the server started\n")
+		fmt.Fprintf(w, "# TYPE uopi_uptime_seconds counter\n")
+		fmt.Fprintf(w, "uopi_uptime_seconds %.3f\n\n", uptime)
+
+		fmt.Fprintf(w, "# HELP uopi_ws_connections Current number of open WebSocket connections\n")
+		fmt.Fprintf(w, "# TYPE uopi_ws_connections gauge\n")
+		fmt.Fprintf(w, "uopi_ws_connections %d\n\n", wsConns.Load())
+
+		fmt.Fprintf(w, "# HELP uopi_signal_subscriptions Current number of unique upstream signal subscriptions\n")
+		fmt.Fprintf(w, "# TYPE uopi_signal_subscriptions gauge\n")
+		fmt.Fprintf(w, "uopi_signal_subscriptions %d\n\n", subs)
+
+		fmt.Fprintf(w, "# HELP uopi_ws_messages_in_total Total WebSocket messages received from clients\n")
+		fmt.Fprintf(w, "# TYPE uopi_ws_messages_in_total counter\n")
+		fmt.Fprintf(w, "uopi_ws_messages_in_total %d\n\n", msgIn.Load())
+
+		fmt.Fprintf(w, "# HELP uopi_ws_messages_out_total Total WebSocket messages sent to clients\n")
+		fmt.Fprintf(w, "# TYPE uopi_ws_messages_out_total counter\n")
+		fmt.Fprintf(w, "uopi_ws_messages_out_total %d\n\n", msgOut.Load())
+
+		fmt.Fprintf(w, "# HELP uopi_write_ops_total Total signal write operations\n")
+		fmt.Fprintf(w, "# TYPE uopi_write_ops_total counter\n")
+		fmt.Fprintf(w, "uopi_write_ops_total %d\n\n", writeOps.Load())
+
+		fmt.Fprintf(w, "# HELP uopi_history_requests_total Total historical data requests served\n")
+		fmt.Fprintf(w, "# TYPE uopi_history_requests_total counter\n")
+		fmt.Fprintf(w, "uopi_history_requests_total %d\n\n", historyReqs.Load())
+	}
+}