上一篇文章介绍了分布式链路的标准 OpenTracing, 在 OpenTracing 的官网我们可以看到这样一条信息 OpenTracing and OpenCensus have merged to form OpenTelemetry!。 可以看到 OpenTracing 和 OpenCensus 已经被合并为 OpenTelemetry 了。

OpenCensus 是什么呢？ OpenTracing 是最早为分布式追踪制定了一套平台无关、厂商无关的协议标准的项目，并以此成为了 CNCF 的孵化项目。 在之后，谷歌牵头，微软加入，创建了 OpenCensus 项目统一 Metrics 基础指标监控的使用方式，还做了 OpenTracing 的老本行：分布式追踪。

OpenTelemetry

OpenTelemetry 的自身定位十分明确：数据采集和标准规范的统一，对于数据如何去使用、存储、展示、告警，官方是不涉及的。

OpenTelemetry 的终极目标十分伟大：实现 Metrics、Tracing、Logging 的融合及大一统，作为 APM 的数据采集终极解决方案。

目前 OpenTelemetry 正式成为 CNCF 的孵化项目，OpenTracing 和 OpenCensus 不再维护, OpenTracing 目前是 CNCF 的存档项目。

OpenTelemetry 的一些基础知识是兼容 OpenTracing 的， 只有一些 API 是不同的。

OpenTelemetry for go

我们继续使用上文的代码, 对上文的代码进行修改。

install 依赖

go get go.opentelemetry.io/[email protected] go.opentelemetry.io/otel/[email protected] go.opentelemetry.io/otel/exporters/stdout/[email protected] go.opentelemetry.io/otel/[email protected]
go get -u go.opentelemetry.io/otel/exporters/jaeger

OpenTelemetry 官方为多种开源框架提供了开箱即用的 Instrumentation Packages ，如 gin , beego , mux , go-kit 等，当然也支持 net/http 标准库 ，更多可浏览opentelemetry-go-contrib 仓库。

我们使用的是 gin, 所以安装相应的依赖 :

go get go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin

对原有代码进行修改， 修改后的代码:

package main

import (
	"context"
	"log"
	"math/rand"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"

	"go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/jaeger"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	tracesdk "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
	"go.opentelemetry.io/otel/trace"
)

var (
	addr = ":8080"
)

// tracerProvider returns an OpenTelemetry TracerProvider configured to use
// the Jaeger exporter that will send spans to the provided url. The returned
// TracerProvider will also use a Resource configured with all the information
// about the application.
func tracerProvider(url string) (*tracesdk.TracerProvider, error) {
	// Create the Jaeger exporter
	exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(url)))
	if err != nil {
		return nil, err
	}
	tp := tracesdk.NewTracerProvider(
		tracesdk.WithSampler(tracesdk.AlwaysSample()),
		tracesdk.WithBatcher(exp),
		tracesdk.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceNameKey.String("opentelemetry-overstarry"), // 服务名
			semconv.ServiceVersionKey.String("0.0.1"),
			attribute.String("environment", "test"),
		)),
	)
	otel.SetTracerProvider(tp)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
	return tp, nil
}

func main() {
	tp, err := tracerProvider("http://localhost:14268/api/traces")
	if err != nil {
		log.Fatal(err)
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Cleanly shutdown and flush telemetry when the application exits.
	defer func(ctx context.Context) {
		// Do not make the application hang when it is shutdown.
		ctx, cancel = context.WithTimeout(ctx, time.Second*5)
		defer cancel()
		if err := tp.Shutdown(ctx); err != nil {
			log.Fatal(err)
		}
	}(ctx)

	engine := gin.New()

	engine.Use(otelgin.Middleware("server"))
	engine.GET("/", indexHandler)
	engine.GET("/home", homeHandler)
	engine.GET("/async", serviceHandler)
	engine.GET("/service", serviceHandler)
	engine.GET("/db", dbHandler)
	err = engine.Run(addr)
	if err != nil {
		return
	}
}

func dbHandler(c *gin.Context) {
	ctx := c.Request.Context()
	span := trace.SpanFromContext(otel.GetTextMapPropagator().Extract(ctx, propagation.HeaderCarrier(c.Request.Header)))
	defer span.End()

	time.Sleep(time.Duration(rand.Intn(200)) * time.Millisecond)
}

func serviceHandler(c *gin.Context) {
	ctx := c.Request.Context()
	// 通过http header，提取span元数据信息
	span := trace.SpanFromContext(otel.GetTextMapPropagator().Extract(ctx, propagation.HeaderCarrier(c.Request.Header)))
	defer span.End()

	dbReq, _ := http.NewRequest("GET", "http://localhost:8080/db", nil)
	otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(dbReq.Header))
	if _, err := http.DefaultClient.Do(dbReq); err != nil {
		span.RecordError(err)
		attribute.String("请求 /db error", err.Error())
	}
	time.Sleep(time.Duration(rand.Intn(200)) * time.Millisecond)
}

func homeHandler(c *gin.Context) {
	c.Header("Content-Type", "text/html; charset=utf-8")

	c.String(200, "开始请求...\n")
	ctx := c.Request.Context()
	// 设置一个根节点 span
	span := trace.SpanFromContext(ctx)
	defer span.End()

	asyncReq, _ := http.NewRequest("GET", "http://localhost:8080/async", nil)
	otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(asyncReq.Header))
	go func() {
		if _, err := http.DefaultClient.Do(asyncReq); err != nil {
			span.RecordError(err)
			span.SetAttributes(attribute.String("请求 /async error", err.Error()))
		}
	}()

	time.Sleep(time.Duration(rand.Intn(200)) * time.Millisecond)

	syncReq, _ := http.NewRequest("GET", "http://localhost:8080/service", nil)
	otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(syncReq.Header))

	if _, err := http.DefaultClient.Do(syncReq); err != nil {
		span.RecordError(err)
		span.SetAttributes(attribute.String("请求 /service error", err.Error()))
	}
	c.String(200, "请求结束！")
}

func indexHandler(c *gin.Context) {
	c.Header("Content-Type", "text/html; charset=utf-8")
	c.String(200, string(`<a href="/home"> 点击发起请求 </a>`))
}

运行项目

代码修改完，现在运行项目，现在访问 Jaeger UI, 可以看到已经有请求调用的链条了。 img.png

小结

今天继续讲了分布式链路追踪的最新标准 OpenTelemetry, 并使用相应 SDK 编写了相应的代码。

相应代码: https://github.com/overstarry/tracing-demo

参考链接