Add span and trace id to hotrod logs (#2384)

Signed-off-by: Joe Elliott <number101010@gmail.com>

examples/hotrod/pkg/log/factory.go

@@ -19,6 +19,7 @@ import (
 	"context"
 
 	"github.com/opentracing/opentracing-go"
+	"github.com/uber/jaeger-client-go"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 )
@@ -44,8 +45,16 @@ func (b Factory) Bg() Logger {
 // echo-ed into the span.
 func (b Factory) For(ctx context.Context) Logger {
 	if span := opentracing.SpanFromContext(ctx); span != nil {
-		// TODO for Jaeger span extract trace/span IDs as fields
-		return spanLogger{span: span, logger: b.logger}
+		logger := spanLogger{span: span, logger: b.logger}
+
+		if jaegerCtx, ok := span.Context().(jaeger.SpanContext); ok {
+			logger.spanFields = []zapcore.Field{
+				zap.String("trace_id", jaegerCtx.TraceID().String()),
+				zap.String("span_id", jaegerCtx.SpanID().String()),
+			}
+		}
+
+		return logger
 	}
 	return b.Bg()
 }

examples/hotrod/pkg/log/spanlogger.go

@@ -26,29 +26,30 @@ import (
 )
 
 type spanLogger struct {
-	logger *zap.Logger
-	span   opentracing.Span
+	logger     *zap.Logger
+	span       opentracing.Span
+	spanFields []zapcore.Field
 }
 
 func (sl spanLogger) Info(msg string, fields ...zapcore.Field) {
 	sl.logToSpan("info", msg, fields...)
-	sl.logger.Info(msg, fields...)
+	sl.logger.Info(msg, append(sl.spanFields, fields...)...)
 }
 
 func (sl spanLogger) Error(msg string, fields ...zapcore.Field) {
 	sl.logToSpan("error", msg, fields...)
-	sl.logger.Error(msg, fields...)
+	sl.logger.Error(msg, append(sl.spanFields, fields...)...)
 }
 
 func (sl spanLogger) Fatal(msg string, fields ...zapcore.Field) {
 	sl.logToSpan("fatal", msg, fields...)
 	tag.Error.Set(sl.span, true)
-	sl.logger.Fatal(msg, fields...)
+	sl.logger.Fatal(msg, append(sl.spanFields, fields...)...)
 }
 
 // With creates a child logger, and optionally adds some context fields to that logger.
 func (sl spanLogger) With(fields ...zapcore.Field) Logger {
-	return spanLogger{logger: sl.logger.With(fields...), span: sl.span}
+	return spanLogger{logger: sl.logger.With(fields...), span: sl.span, spanFields: sl.spanFields}
 }
 
 func (sl spanLogger) logToSpan(level string, msg string, fields ...zapcore.Field) {