log-trace-connector demo

log-trace-connector.go

package main
// live https://goplay.space/#qUqusVmj8oV

import (
	"context"
	"fmt"
)

func NewService(l *Logger) *Service {
	return &Service{
		logger: func(ctx context.Context) *Logger {
			// create a new context logger from the existing
			ll := &Logger{l.fields}
			return LogWithTracing(ctx, ll)
		},
	}
}

func (s *Service) ServiceMethod(ctx context.Context, source string) {
	s.logger(ctx).Log(source)
}

type Logger struct {
	fields string
}

func (l *Logger) Log(s string) {
	fmt.Println("LOG::fields->[" + l.fields + "] :: s=" + s)
}
func (l *Logger) AddField(f string, val string) {
	l.fields = l.fields + fmt.Sprintf(" %s=%s", f, val)
}

type Service struct {
	logger func(ctx context.Context) *Logger
}

func LogWithTracing(ctx context.Context, l *Logger) *Logger {
	l.AddField("LogWithTracing", "worked")
	if v := ctx.Value(ctxMarkerKey); v != nil {
		l.AddField("ctx_value", v.(string))
	}

	return l
}

type ctxMarker struct{}

var (
	ctxMarkerKey = &ctxMarker{}
)

func main() {
	fmt.Println("Start.")
	l := &Logger{}
	l.Log("simple log")
	s := NewService(l)
	c1 := context.Background()
	s.ServiceMethod(c1, "Call to ServiceMethod_1")
	// Immitate tracer injected tracing context into a request context
	c2 := context.WithValue(c1, ctxMarkerKey, "tracing_context")

	s.ServiceMethod(c2, "Call to ServiceMethod_2")
}