telemetry/console.go

package telemetry

import (
	"context"
	"errors"

	"go.opentelemetry.io/otel"
	otellog "go.opentelemetry.io/otel/log"
	"go.opentelemetry.io/otel/log/global"
	"go.opentelemetry.io/otel/propagation"
	sdklog "go.opentelemetry.io/otel/sdk/log"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"

	"code.nochebuena.dev/go/logz"
)

// ConsoleConfig holds the minimum OTel configuration needed for console/dev mode.
// Only service identity fields are required — no OTLP endpoint.
type ConsoleConfig struct {
	ServiceName    string `env:"OTEL_SERVICE_NAME,required"`
	ServiceVersion string `env:"OTEL_SERVICE_VERSION" envDefault:"unknown"`
	Environment    string `env:"OTEL_ENVIRONMENT"     envDefault:"development"`
}

// NewConsole bootstraps the OTel SDK with logz-backed exporters for local development.
// All signals (traces, metrics, OTel log records) are emitted as structured logz log
// lines instead of being sent to a collector.
//
// Drop-in alternative to [New] for development environments.
//
// Warning: do not wire the OTel slog bridge alongside NewConsole — routing logz through
// the OTel log API and back through logLogExporter creates a feedback loop.
func NewConsole(ctx context.Context, logger logz.Logger, cfg ConsoleConfig) (func(context.Context) error, error) {
	res, err := resource.Merge(
		resource.Default(),
		resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceName(cfg.ServiceName),
			semconv.ServiceVersion(cfg.ServiceVersion),
		),
	)
	if err != nil {
		res = resource.Default()
	}

	tp := sdktrace.NewTracerProvider(
		sdktrace.WithSyncer(&logTraceExporter{logger: logger}),
		sdktrace.WithResource(res),
	)
	otel.SetTracerProvider(tp)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	))

	mp := sdkmetric.NewMeterProvider(
		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(&logMetricExporter{logger: logger})),
		sdkmetric.WithResource(res),
	)
	otel.SetMeterProvider(mp)

	lp := sdklog.NewLoggerProvider(
		sdklog.WithProcessor(sdklog.NewBatchProcessor(&logLogExporter{logger: logger})),
		sdklog.WithResource(res),
	)
	global.SetLoggerProvider(lp)

	shutdown := func(ctx context.Context) error {
		var errs []error
		if err := tp.Shutdown(ctx); err != nil {
			errs = append(errs, &providerErr{"trace", err})
		}
		if err := mp.Shutdown(ctx); err != nil {
			errs = append(errs, &providerErr{"metric", err})
		}
		if err := lp.Shutdown(ctx); err != nil {
			errs = append(errs, &providerErr{"log", err})
		}
		return errors.Join(errs...)
	}
	return shutdown, nil
}

// --- trace exporter ---

type logTraceExporter struct{ logger logz.Logger }

func (e *logTraceExporter) ExportSpans(_ context.Context, spans []sdktrace.ReadOnlySpan) error {
	for _, s := range spans {
		e.logger.Info("otel: span",
			"name", s.Name(),
			"trace_id", s.SpanContext().TraceID(),
			"span_id", s.SpanContext().SpanID(),
			"parent_span_id", s.Parent().SpanID(),
			"kind", s.SpanKind(),
			"duration_ms", s.EndTime().Sub(s.StartTime()).Milliseconds(),
			"status", s.Status().Code,
		)
	}
	return nil
}

func (e *logTraceExporter) Shutdown(_ context.Context) error { return nil }

// --- metric exporter ---

type logMetricExporter struct{ logger logz.Logger }

func (e *logMetricExporter) Temporality(_ sdkmetric.InstrumentKind) metricdata.Temporality {
	return metricdata.CumulativeTemporality
}

func (e *logMetricExporter) Aggregation(k sdkmetric.InstrumentKind) sdkmetric.Aggregation {
	return sdkmetric.DefaultAggregationSelector(k)
}

func (e *logMetricExporter) Export(_ context.Context, rm *metricdata.ResourceMetrics) error {
	for _, sm := range rm.ScopeMetrics {
		for _, m := range sm.Metrics {
			e.logMetric(m)
		}
	}
	return nil
}

func (e *logMetricExporter) logMetric(m metricdata.Metrics) {
	switch d := m.Data.(type) {
	case metricdata.Sum[int64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "sum", "value", dp.Value, "unit", m.Unit)
		}
	case metricdata.Sum[float64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "sum", "value", dp.Value, "unit", m.Unit)
		}
	case metricdata.Gauge[int64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "gauge", "value", dp.Value, "unit", m.Unit)
		}
	case metricdata.Gauge[float64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "gauge", "value", dp.Value, "unit", m.Unit)
		}
	case metricdata.Histogram[int64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "histogram", "count", dp.Count, "sum", dp.Sum, "unit", m.Unit)
		}
	case metricdata.Histogram[float64]:
		for _, dp := range d.DataPoints {
			e.logger.Info("otel: metric", "name", m.Name, "kind", "histogram", "count", dp.Count, "sum", dp.Sum, "unit", m.Unit)
		}
	}
}

func (e *logMetricExporter) ForceFlush(_ context.Context) error { return nil }
func (e *logMetricExporter) Shutdown(_ context.Context) error   { return nil }

// --- log exporter ---

type logLogExporter struct{ logger logz.Logger }

func (e *logLogExporter) Export(_ context.Context, records []sdklog.Record) error {
	for _, r := range records {
		body := r.Body().AsString()
		sev := r.Severity()
		switch {
		case sev >= otellog.SeverityError:
			e.logger.Error("otel: log", nil, "body", body, "severity", r.SeverityText())
		case sev >= otellog.SeverityWarn:
			e.logger.Warn("otel: log", "body", body, "severity", r.SeverityText())
		default:
			e.logger.Info("otel: log", "body", body, "severity", r.SeverityText())
		}
	}
	return nil
}

func (e *logLogExporter) ForceFlush(_ context.Context) error { return nil }
func (e *logLogExporter) Shutdown(_ context.Context) error   { return nil }