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gRPC & High Performance APIs · 课时

使用 OpenTelemetry 进行追踪

集成 OpenTelemetry，实现分布式追踪，将跨服务的端到端请求流转可视化

使用 OpenTelemetry 进行追踪 是 CoddyKit 上的免费 gRPC & High Performance APIs 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 gRPC & High Performance APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 gRPC & High Performance APIs 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Microservices & The Tracing Need

Modern applications often consist of many small, interconnected services, known as microservices. This architecture offers flexibility but can make debugging complex interactions a real challenge.

When a user request travels through several services, pinpointing where a delay or error occurred becomes like finding a needle in a haystack.

Following the Request Path

Distributed tracing helps you visualize the entire journey of a request as it flows through different services in your system.

  • It links all operations related to a single request.
  • It shows the time taken by each part of the request.
  • This helps identify performance bottlenecks and errors across service boundaries.

OpenTelemetry: The Observability Standard

OpenTelemetry (OTel) is an open-source project that provides a standardized way to collect telemetry data from your applications. This includes traces, metrics, and logs.

Instead of vendor-specific SDKs, OTel offers a single set of APIs, SDKs, and tools to instrument your services, making your observability data portable.

Traces Built from Spans

In OpenTelemetry, a trace represents the complete execution path of a request through your system. It's like the entire story of that request.

A trace is composed of one or more spans. Each span represents a single operation or unit of work within that trace, like a step in the story. Spans have a start time, end time, and metadata.

Propagating Trace Context

For spans to form a complete trace across different services, they need to be linked. This is done through context propagation.

When a service calls another, it passes along a "trace context" (often in HTTP/2 headers for gRPC). This context tells the receiving service which trace and parent span its new operations belong to, creating a parent-child relationship between spans.

OTel Tracing Essentials

To implement tracing, you'll work with these core OpenTelemetry components:

  • TracerProvider: Manages Tracer instances and configures span processors and exporters.
  • Tracer: Creates Span objects.
  • SpanProcessor: Processes spans before they are exported (e.g., batching).
  • Exporter: Sends collected spans to a backend (like a console, Jaeger, or OTLP collector).

OTel Setup: TracerProvider & Exporter

Let's set up a basic OpenTelemetry TracerProvider in Go. We'll use a simple stdouttrace exporter to print trace data to the console, so you can see the spans being generated.

This snippet initializes the global TracerProvider and ensures all spans are flushed when the application exits.

Run this code to see the basic setup:

package main

import (
	"context"
	"log"
	"os"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
	"go.opentelemetry.io/otel/trace"
)

// initTracerProvider initializes an OpenTelemetry TracerProvider
// with a stdout exporter for demonstration.
func initTracerProvider() *sdktrace.TracerProvider {
	// Create stdout exporter to print traces to the console
	exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
	if err != nil {
		log.Fatalf("failed to create stdout exporter: %v", err)
	}

	// Create a new TracerProvider with the exporter and a service name
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter), // Batch spans for efficiency
		sdktrace.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceName("my-simple-service"),
			attribute.String("environment", "development"),
		)),
	)
	otel.SetTracerProvider(tp) // Set the global TracerProvider

	return tp
}

func main() {
	tp := initTracerProvider()
	defer func() {
		if err := tp.Shutdown(context.Background()); err != nil {
			log.Fatalf("Error shutting down tracer provider: %v", err)
		}
	}()

	// Get a tracer
	tracer := otel.Tracer("my-app-tracer")

	// Create a root span
	ctx, span := tracer.Start(context.Background(), "main-operation")
	defer span.End()

	log.Println("Hello from main-operation with tracing enabled!")
	time.Sleep(100 * time.Millisecond) // Simulate some work

	// Create a child span
	_, childSpan := tracer.Start(ctx, "sub-operation")
	defer childSpan.End()
	childSpan.SetAttributes(attribute.String("task", "processing"))
	log.Println("Doing some sub-operation...")
	time.Sleep(50 * time.Millisecond) // Simulate more work

	log.Println("Trace data will be printed on shutdown.")
}

Auto-Tracing gRPC Calls

To automatically trace gRPC requests, OpenTelemetry provides interceptors. These are middleware functions that wrap gRPC calls on both the client and server sides.

  • Server interceptor: Starts a new span for incoming requests, linking it to the trace context from the client.
  • Client interceptor: Injects the current trace context into outgoing requests, allowing propagation to the server.

Here's how you'd apply them to your gRPC server and client:

package main

import (
	"context"
	"log"
	"net"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	// OpenTelemetry imports
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"

	// gRPC OpenTelemetry instrumentation
	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"

	// For this example, we'll define a simple service in-line
	pb "google.golang.org/grpc/examples/helloworld/helloworld" // Using a standard example proto
)

// initTracerProvider initializes an OpenTelemetry TracerProvider
// with a stdout exporter for demonstration.
func initTracerProvider() *sdktrace.TracerProvider {
	exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
	if err != nil {
		log.Fatalf("failed to create stdout exporter: %v", err)
	}

	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceName("grpc-otel-demo"),
			attribute.String("environment", "development"),
		)),
	)
	otel.SetTracerProvider(tp)
	return tp
}

// helloServer is a simple gRPC server for demonstration
type helloServer struct {
	pb.UnimplementedGreeterServer
}

func (s *helloServer) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	log.Printf("Received: %v", in.GetName())
	// Simulate some work
	time.Sleep(50 * time.Millisecond)
	return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil
}

func main() {
	// 1. Initialize OpenTelemetry TracerProvider
	tp := initTracerProvider()
	defer func() {
		if err := tp.Shutdown(context.Background()); err != nil {
			log.Fatalf("Error shutting down tracer provider: %v", err)
		}
	}()

	// 2. Start gRPC Server with OpenTelemetry Interceptor
	lis, err := net.Listen("tcp", ":50051")
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer(
		grpc.UnaryInterceptor(otelgrpc.UnaryServerInterceptor()), // Apply OTel server interceptor
	)
	pb.RegisterGreeterServer(s, &helloServer{})
	log.Println("Server listening on :50051")
	go func() {
		if err := s.Serve(lis); err != nil {
			log.Fatalf("failed to serve: %v", err)
		}
	}()
	defer s.Stop()

	// Allow server to start
	time.Sleep(1 * time.Second)

	// 3. Create gRPC Client with OpenTelemetry Interceptor
	conn, err := grpc.Dial(
		"localhost:50051",
		grpc.WithInsecure(), // For simplicity, use insecure
		grpc.WithBlock(),
		grpc.WithUnaryInterceptor(otelgrpc.UnaryClientInterceptor()), // Apply OTel client interceptor
	)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	c := pb.NewGreeterClient(conn)

	// 4. Make a gRPC call
	log.Println("Making gRPC call...")
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: "CoddyKit User"})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %s", r.GetMessage())

	// Give some time for spans to be processed and exported
	time.Sleep(1 * time.Second)
	log.Println("Trace data should now be visible in console.")
}

Reading the Trace Story

After running the previous example, you'll see a detailed JSON output in your console. This output represents the trace data.

  • Look for "TraceID": This unique ID links all spans belonging to the same request.
  • Each entry is a "Span": It has a "SpanID", "ParentSpanID" (if it's not the root), name, start/end times, and attributes.
  • The hierarchy of spans (parent-child) shows the flow of execution.

This "story" helps you understand how long each step took and which service was responsible.

Enriching Spans with Attributes

While auto-instrumentation provides basic spans, you often need to add more specific information to your traces. Span attributes (key-value pairs) allow you to do this.

You can record details like user IDs, request parameters, or specific business logic outcomes directly on a span. This makes debugging and analysis much more effective.

Use span.SetAttributes() to add custom attributes.

package main

import (
	"context"
	"log"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
	"go.opentelemetry.io/otel/trace"
)

// initTracerProvider initializes an OpenTelemetry TracerProvider
func initTracerProvider() *sdktrace.TracerProvider {
	exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
	if err != nil {
		log.Fatalf("failed to create stdout exporter: %v", err)
	}
	tp := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceName("custom-attributes-demo"),
		)),
	)
	otel.SetTracerProvider(tp)
	return tp
}

func main() {
	tp := initTracerProvider()
	defer func() {
		if err := tp.Shutdown(context.Background()); err != nil {
			log.Fatalf("Error shutting down tracer provider: %v", err)
		}
	}()

	tracer := otel.Tracer("my-custom-tracer")

	// Start a root span
	ctx, span := tracer.Start(context.Background(), "process-order")
	defer span.End()

	// Add custom attributes to the root span
	span.SetAttributes(
		attribute.String("user.id", "user123"),
		attribute.Int("order.id", 45678),
		attribute.Bool("is_premium_user", true),
	)
	log.Println("Processing order with custom attributes...")
	time.Sleep(100 * time.Millisecond)

	// Create a child span
	_, childSpan := tracer.Start(ctx, "database-query")
	defer childSpan.End()
	childSpan.SetAttributes(
		attribute.String("db.system", "postgres"),
		attribute.String("db.statement", "SELECT * FROM orders WHERE id=45678"),
	)
	log.Println("Executing database query...")
	time.Sleep(50 * time.Millisecond)

	log.Println("Check the console output for custom attributes in the spans!")
	time.Sleep(500 * time.Millisecond) // Ensure spans are exported
}

Tracing Concepts Check

You've learned about distributed tracing and how OpenTelemetry helps. Let's test your understanding.

Tracing with OpenTelemetry Recap

In this lesson, you learned how distributed tracing helps navigate the complexities of microservices by showing the full journey of a request.

We explored OpenTelemetry as the standard for collecting traces, understanding core concepts like traces, spans, and context propagation. You saw how to set up an OTel TracerProvider and how gRPC interceptors make instrumenting your services straightforward. Finally, we covered enriching your spans with custom attributes for deeper insights.

With OpenTelemetry, you gain crucial visibility into your gRPC application's behavior!

常见问题解答

「使用 OpenTelemetry 进行追踪」课时是免费的吗？

是的 — 「使用 OpenTelemetry 进行追踪」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 gRPC & High Performance APIs 课程的其余内容，请升级到 CoddyKit PRO。 gRPC & High Performance APIs 课程共包含 4 节课。

「使用 OpenTelemetry 进行追踪」这节课中我会学到什么？

集成 OpenTelemetry，实现分布式追踪，将跨服务的端到端请求流转可视化 你通过在浏览器中直接运行的动手代码来练习 gRPC & High Performance APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 gRPC & High Performance APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 gRPC & High Performance APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。

「使用 OpenTelemetry 进行追踪」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 gRPC & High Performance APIs 课中编写并运行代码吗？

能。每节 gRPC & High Performance APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 记录 gRPC 交互日志
  2. 使用 OpenTelemetry 进行追踪
  3. 监控 gRPC 指标
  4. 健康检查与就绪探针
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