Add telemetry

internal/telemetry/metrics.go

@@ -0,0 +1,50 @@
+package telemetry
+
+import (
+	"go.opentelemetry.io/otel/metric"
+)
+
+var (
+	RequestCounter      metric.Int64Counter
+	RequestDuration     metric.Float64Histogram
+	RequestBodySize     metric.Int64Histogram
+	UpstreamErrors      metric.Int64Counter
+	TokensInput         metric.Int64Counter
+	TokensOutput        metric.Int64Counter
+	CredentialCooldowns metric.Int64Counter
+	ActiveCredentials   metric.Int64UpDownCounter
+	StreamRequests      metric.Int64Counter
+)
+
+// InitMetrics creates all metric instruments from the given meter.
+func InitMetrics(meter metric.Meter) {
+	RequestCounter, _ = meter.Int64Counter("proxy.request.count",
+		metric.WithDescription("Total proxy requests"),
+	)
+	RequestDuration, _ = meter.Float64Histogram("proxy.request.duration_ms",
+		metric.WithDescription("Request latency in milliseconds"),
+		metric.WithUnit("ms"),
+	)
+	RequestBodySize, _ = meter.Int64Histogram("proxy.request.body_size_bytes",
+		metric.WithDescription("Request body size in bytes"),
+		metric.WithUnit("By"),
+	)
+	UpstreamErrors, _ = meter.Int64Counter("proxy.upstream.errors",
+		metric.WithDescription("Upstream error count"),
+	)
+	TokensInput, _ = meter.Int64Counter("proxy.tokens.input",
+		metric.WithDescription("Input tokens consumed"),
+	)
+	TokensOutput, _ = meter.Int64Counter("proxy.tokens.output",
+		metric.WithDescription("Output tokens consumed"),
+	)
+	CredentialCooldowns, _ = meter.Int64Counter("proxy.credential.cooldowns",
+		metric.WithDescription("Credential cooldown activations"),
+	)
+	ActiveCredentials, _ = meter.Int64UpDownCounter("proxy.credential.active",
+		metric.WithDescription("Currently active (non-cooldown) credentials"),
+	)
+	StreamRequests, _ = meter.Int64Counter("proxy.stream.requests",
+		metric.WithDescription("Streaming request count"),
+	)
+}