feat(OpenTelemetry): Integrate OpenTelemetry into agent (#90)

* feat(OpenTelemetry): Integrate OpenTelemetry into agent

- integrate OpenTelemetry logging with zap logger for better observability
- add OpenTelemetry gRPC middleware for enhanced tracing capabilities
- document new OTLP exporter endpoint for better configuration guidance

* docs: document OTEL env var

---------

Co-authored-by: Cedric Kienzler <cedric@specht-labs.de>

pkg/agent/state.go

@@ -7,6 +7,7 @@ import (
 	"github.com/compute-blade-community/compute-blade-agent/pkg/events"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/spechtlabs/go-otel-utils/otelzap"
 	"go.uber.org/zap"
 )
 
@@ -63,7 +64,7 @@ func (s *computebladeStateImpl) RegisterEvent(event events.Event) {
 		s.criticalConfirmChan = make(chan struct{})
 
 	default:
-		zap.L().Warn("Unknown event", zap.String("event", event.String()))
+		otelzap.L().Warn("Unknown event", zap.String("event", event.String()))
 	}
 
 	// Set identify state metric

pkg/hal/hal_bcm2711.go

@@ -199,7 +199,7 @@ func (bcm *bcm2711) setup(ctx context.Context) error {
 			return err
 		}
 	} else {
-		log.FromContext(ctx).Info("no smart fan unit detected, assuming standard fan unit", zap.Error(err))
+		log.FromContext(ctx).WithError(err).Info("no smart fan unit detected, assuming standard fan unit")
 		// FAN PWM output for standard fan unit (GPIO 12)
 		// -> bcm2711RegGpfsel1 8:6, alt0
 		bcm.gpioMem[bcm2711RegGpfsel1] = (bcm.gpioMem[bcm2711RegGpfsel1] &^ (0b111 << 6)) | (0b100 << 6)
@@ -258,7 +258,7 @@ func (bcm *bcm2711) WaitForEdgeButtonPress(parentCtx context.Context) error {
 	go func() {
 		err := bcm.fanUnit.WaitForButtonPress(ctx)
 		if err != nil && err != context.Canceled {
-			log.FromContext(ctx).Error("failed to wait for button press", zap.Error(err))
+			log.FromContext(ctx).WithError(err).Error("failed to wait for button press")
 		} else {
 			close(fanUnitChan)
 		}

pkg/hal/hal_bcm2711_simulated.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/compute-blade-community/compute-blade-agent/pkg/hal/led"
+	"github.com/spechtlabs/go-otel-utils/otelzap"
 	"go.uber.org/zap"
 )
 
@@ -19,7 +20,7 @@ type SimulatedHal struct {
 }
 
 func NewCm4Hal(_ context.Context, _ ComputeBladeHalOpts) (ComputeBladeHal, error) {
-	logger := zap.L().Named("hal").Named("simulated-cm4")
+	logger := otelzap.L().Named("hal").Named("simulated-cm4")
 	logger.Warn("Using simulated hal")
 
 	computeModule.WithLabelValues("simulated").Set(1)

pkg/hal/hal_bcm2711_standardfanunit.go

@@ -4,9 +4,10 @@ package hal
 
 import (
 	"context"
+	"math"
+
 	"github.com/compute-blade-community/compute-blade-agent/pkg/log"
 	"go.uber.org/zap"
-	"math"
 
 	"github.com/compute-blade-community/compute-blade-agent/pkg/hal/led"
 	"github.com/warthog618/gpiod"

pkg/hal/smartfanunit.go

@@ -14,7 +14,6 @@ import (
 	"github.com/compute-blade-community/compute-blade-agent/pkg/smartfanunit"
 	"github.com/compute-blade-community/compute-blade-agent/pkg/smartfanunit/proto"
 	"go.bug.st/serial"
-	"go.uber.org/zap"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -32,7 +31,7 @@ func SmartFanUnitPresent(ctx context.Context, portName string) (bool, error) {
 	defer func(rwc serial.Port) {
 		err := rwc.Close()
 		if err != nil {
-			log.FromContext(ctx).Warn("Error while closing serial port", zap.Error(err))
+			log.FromContext(ctx).WithError(err).Warn("Error while closing serial port")
 		}
 	}(rwc)
 
@@ -42,7 +41,7 @@ func SmartFanUnitPresent(ctx context.Context, portName string) (bool, error) {
 		log.FromContext(ctx).Warn("Closing serial port")
 		err := rwc.Close()
 		if err != nil {
-			log.FromContext(ctx).Warn("Error while closing serial port", zap.Error(err))
+			log.FromContext(ctx).WithError(err).Warn("Error while closing serial port")
 		}
 	}()
 
@@ -117,7 +116,7 @@ func (fuc *smartFanUnit) Run(parentCtx context.Context) error {
 
 			pkt, err := proto.ReadPacket(ctx, fuc.rwc)
 			if err != nil {
-				log.FromContext(ctx).Error("Failed to read packet from serial port", zap.Error(err))
+				log.FromContext(ctx).WithError(err).Error("Failed to read packet from serial port")
 				continue
 			}
 			fuc.eb.Publish(inboundTopic, pkt)

pkg/log/interceptor_logger.go

@@ -4,12 +4,13 @@ import (
 	"context"
 
 	"github.com/grpc-ecosystem/go-grpc-middleware/v2/interceptors/logging"
+	"github.com/spechtlabs/go-otel-utils/otelzap"
 	"go.uber.org/zap"
 )
 
 // InterceptorLogger adapts zap logger to interceptor logger.
 // This code is simple enough to be copied and not imported.
-func InterceptorLogger(l *zap.Logger) logging.Logger {
+func InterceptorLogger(l *otelzap.Logger) logging.Logger {
 	return logging.LoggerFunc(func(ctx context.Context, lvl logging.Level, msg string, fields ...any) {
 		f := make([]zap.Field, 0, len(fields)/2)
 
@@ -24,12 +25,14 @@ func InterceptorLogger(l *zap.Logger) logging.Logger {
 				f = append(f, zap.Int(key.(string), v))
 			case bool:
 				f = append(f, zap.Bool(key.(string), v))
+			case zap.Field:
+				f = append(f, v)
 			default:
 				f = append(f, zap.Any(key.(string), v))
 			}
 		}
 
-		logger := zap.L().WithOptions(zap.AddCallerSkip(4)).With(f...)
+		logger := l.WithOptions(zap.AddCallerSkip(4)).With(f...)
 
 		switch lvl {
 		case logging.LevelDebug:

pkg/log/logger.go

@@ -3,21 +3,22 @@ package log
 import (
 	"context"
 
+	"github.com/spechtlabs/go-otel-utils/otelzap"
 	"go.uber.org/zap"
 )
 
 type logCtxKey int
 
-func IntoContext(ctx context.Context, logger *zap.Logger) context.Context {
+func IntoContext(ctx context.Context, logger *otelzap.Logger) context.Context {
 	return context.WithValue(ctx, logCtxKey(0), logger)
 }
 
-func FromContext(ctx context.Context) *zap.Logger {
+func FromContext(ctx context.Context) *otelzap.Logger {
 	val := ctx.Value(logCtxKey(0))
 	if val != nil {
-		return val.(*zap.Logger)
+		return val.(*otelzap.Logger)
 	}
 
-	zap.L().WithOptions(zap.AddCallerSkip(1)).Warn("No logger in context, passing default")
-	return zap.L()
+	otelzap.L().WithOptions(zap.AddCallerSkip(1)).Warn("No logger in context, passing default")
+	return otelzap.L()
 }