分布式链路追踪实战篇-日志库集成opentelemetry的思路

由上文分布式链路追踪入门篇-基础原理与快速应用可以知道分布式链路追踪的作用，但是距离应用到项目中，我们还需要对项目中一些关键组件进行opentelemetry的集成，例如日志库，ORM、http框架、rpc框架等。

一、日志库如何集成opentelemetry？

其实对日志库的集成无非就是调用日志库的方法进行日志打印时，可以把日志信息也被记录下来，推送到可视化的后端（eg:jaeger）。而由上文分布式链路追踪入门篇-基础原理与快速应用可以知道，通过span可以关联上相关的操作信息

二、简单demo演示

例如就对我们go原生的log库进行封装：

log.go

package pkgimport (`context``log``os``go.opentelemetry.io/otel/attribute``go.opentelemetry.io/otel/trace`
)//封装一下日志
type Logger struct {log *log.Logger
}var Log *Loggerfunc init()  {Log = &Logger{log: log.New(os.Stderr, "", log.LstdFlags),}
}func (l *Logger) Debug(ctx context.Context, msg string) {span := trace.SpanFromContext(ctx)span.AddEvent("", trace.WithAttributes(attribute.String("log", msg)))l.log.Println(msg)
}//todo 原生日志库只有Print方法，没有INFO、WARNd等分级
func (l *Logger) Info(ctx context.Context, msg string) {}
//todo
func (l *Logger) Warn(ctx context.Context, msg string) {}
//todo
func (l *Logger) Error(ctx context.Context, msg string) {}
//todo
func (l *Logger) Fatal(ctx context.Context, msg string) {}

main.go

package mainimport ("context""fmt""log""net/http""go.opentelemetry.io/otel""go.opentelemetry.io/otel/exporters/trace/jaeger"`go.opentelemetry.io/otel/sdk/resource`sdktrace "go.opentelemetry.io/otel/sdk/trace"`go.opentelemetry.io/otel/semconv``otel/log/pkg`
)// 初始化 OpenTelemetry
func initTracer() *sdktrace.TracerProvider {exporter, err := jaeger.NewRawExporter(jaeger.WithAgentEndpoint(func(options *jaeger.AgentEndpointOptions) {options.Host = "localhost"options.Port = "6831"}),)if err != nil {log.Fatalf("Error creating Jaeger exporter: %v", err)}tp := sdktrace.NewTracerProvider(sdktrace.WithBatcher(exporter),sdktrace.WithSampler(sdktrace.AlwaysSample()),sdktrace.WithResource(resource.NewWithAttributes(semconv.ServiceNameKey.String("demo_service"), // 服务名)),)otel.SetTracerProvider(tp)return tp
}func main() {tp := initTracer()defer func() {if cerr := tp.Shutdown(context.Background()); cerr != nil {log.Fatalf("Error shutting down tracer provider: %v", cerr)}}()//启动http服务器http.HandleFunc("/log/demo", handleRequest)go func() {if err := http.ListenAndServe(":8080", nil); err != nil {log.Fatalf("Error starting Service A server: %v", err)}}()//模拟请求SimulateRequest()
}func SimulateRequest()  {req, err := http.NewRequest("GET", "http://localhost:8080/log/demo", nil)if err != nil {log.Fatalf("Creating request fail: %v", err)}resp, err := http.DefaultClient.Do(req)if err != nil {log.Fatalf("Request failed: %v", err)}defer resp.Body.Close()fmt.Println("Response received from Root Service")
}func handleRequest(w http.ResponseWriter, req *http.Request) {tracer := otel.Tracer("root")//开始创建root spanctx, span := tracer.Start(req.Context(), "root service")defer span.End()pkg.Log.Debug(ctx, "this is root service")//访问服务AcallServiceA(ctx)w.WriteHeader(http.StatusOK)fmt.Fprintf(w, "Response from Service Root")
}// Service A
func callServiceA(ctx context.Context) {tracer := otel.Tracer("service A")ctx, span := tracer.Start(ctx, "ServiceA")defer span.End()pkg.Log.Debug(ctx, "this is A service")fmt.Println("Service A")
}

运行程序后，访问jeager：

三、总结

1. 其实日志库的集成就是对原先的日志库进行一层封装，日志打印方法传入上下文，通过上下文获取到操作单元span，然后给span关联上日志信息
2. 上面demo只是一个演示，我们也可以依照这个思路封装我们自己项目中的日志库