✨ Integrate monitoring server for observability, adding health and metrics endpoints. Update configuration to enable monitoring features and enhance README with deployment examples for Kubernetes and systemd. Refactor application initialization to include monitoring server setup and improve error handling in message processing metrics.

internal/observability/metrics/metrics.go

@@ -0,0 +1,71 @@
+package metrics
+
+import (
+	"math"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	once             sync.Once
+	registry         *prometheus.Registry
+	processedCounter *prometheus.CounterVec
+	failureCounter   *prometheus.CounterVec
+	parseLatency     *prometheus.HistogramVec
+)
+
+func initCollectors() {
+	registry = prometheus.NewRegistry()
+	processedCounter = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "caatsm_processed_total",
+		Help: "Count of telegrams processed by status and category.",
+	}, []string{"status", "category"})
+	failureCounter = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "caatsm_failures_total",
+		Help: "Count of processor failures by stage (parser, repository, publisher).",
+	}, []string{"stage"})
+	parseLatency = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "caatsm_parse_latency_seconds",
+		Help:    "Latency between reception and parse completion.",
+		Buckets: prometheus.DefBuckets,
+	}, []string{"status", "category"})
+
+	registry.MustRegister(processedCounter, failureCounter, parseLatency)
+}
+
+func ensureCollectors() {
+	once.Do(initCollectors)
+}
+
+// Handler exposes the Prometheus metrics registry.
+func Handler() http.Handler {
+	ensureCollectors()
+	return promhttp.HandlerFor(registry, promhttp.HandlerOpts{})
+}
+
+// RecordProcessed tracks the final status of a telegram along with the parse latency.
+func RecordProcessed(status, category string, elapsed time.Duration) {
+	ensureCollectors()
+	processedCounter.WithLabelValues(labelValue(status), labelValue(category)).Inc()
+	seconds := math.Max(elapsed.Seconds(), 0)
+	parseLatency.WithLabelValues(labelValue(status), labelValue(category)).Observe(seconds)
+}
+
+// RecordFailure increments the failure counter for the supplied stage.
+func RecordFailure(stage string) {
+	ensureCollectors()
+	failureCounter.WithLabelValues(labelValue(stage)).Inc()
+}
+
+func labelValue(value string) string {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return "unknown"
+	}
+	return strings.ToLower(value)
+}