OpenTelemetry Java：实现跨服务Span上下文传播

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.api.baggage.Baggage;
import io.opentelemetry.context.propagation.TextMapSetter;

import java.util.HashMap;
import java.util.Map;

public class SenderService {

    private final OpenTelemetry openTelemetry;
    private final Tracer tracer;

    public SenderService(OpenTelemetry openTelemetry) {
        this.openTelemetry = openTelemetry;
        this.tracer = openTelemetry.getTracer("SenderService");
    }

    public Map<String, String> makeRemoteCall(String serviceName) {
        // 1. 创建一个Span，并使其成为当前活动的Span
        Span span = tracer.spanBuilder("sendTo" + serviceName)
                .startSpan();

        Map<String, String> headers = new HashMap<>(); // 模拟HTTP请求头

        try (Scope scope = span.makeCurrent()) {
            // 2. 获取当前Context，其中包含活动的Span
            Context currentContext = Context.current();

            // 3. 使用TextMapPropagator将Context注入到headers中
            openTelemetry.getPropagators().getTextMapPropagator().inject(
                    currentContext,
                    headers,
                    new TextMapSetter<Map<String, String>>() {
                        @Override
                        public void set(Map<String, String> carrier, String key, String value) {
                            carrier.put(key, value);
                        }
                    });

            System.out.println("Sender Span ID: " + span.getSpanContext().getSpanId());
            System.out.println("Injected headers: " + headers);

            // 模拟执行一些业务逻辑
            // ...

        } finally {
            span.end(); // 结束Span
        }
        return headers;
    }

    public static void main(String[] args) {
        // 通常OpenTelemetry实例会在应用启动时初始化
        // 这里为了示例方便，简单创建
        OpenTelemetry openTelemetry = OpenTelemetry.noop(); // 实际应用中会使用SDK初始化

        SenderService sender = new SenderService(openTelemetry);
        sender.makeRemoteCall("ReceiverService");
    }
}

import io.opentelemetry.api.OpenTelemetry;
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.context.propagation.TextMapGetter;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class ReceiverService {

    private final OpenTelemetry openTelemetry;
    private final Tracer tracer;

    public ReceiverService(OpenTelemetry openTelemetry) {
        this.openTelemetry = openTelemetry;
        this.tracer = openTelemetry.getTracer("ReceiverService");
    }

    public void processRemoteCall(Map<String, String> headers) {
        // 1. 从接收到的请求头中提取Context
        Context extractedContext = openTelemetry.getPropagators().getTextMapPropagator().extract(
                Context.current(), // 默认的当前Context，如果不存在父Context，则使用它
                headers,
                new TextMapGetter<Map<String, String>>() {
                    @Override
                    public Iterable<String> keys(Map<String, String> carrier) {
                        return carrier.keySet();
                    }

                    @Override
                    public String get(Map<String, String> carrier, String key) {
                        return carrier.get(key);
                    }
                });

        // 2. 将提取到的Context设置为新Span的父级
        // 注意：这里不是直接传入Span对象，而是传入包含父Span信息的Context
        Span span = tracer.spanBuilder("processRequest")
                .setParent(extractedContext) // 将提取到的Context作为父级
                .startSpan();

        try (Scope scope = span.makeCurrent()) {
            System.out.println("Receiver Span ID: " + span.getSpanContext().getSpanId());
            System.out.println("Receiver Parent Span ID (from Context): " + Span.fromContext(extractedContext).getSpanContext().getSpanId());
            // 模拟执行一些业务逻辑
            // ...
        } finally {
            span.end(); // 结束Span
        }
    }

    public static void main(String[] args) {
        OpenTelemetry openTelemetry = OpenTelemetry.noop(); // 实际应用中会使用SDK初始化

        // 模拟从SenderService接收到的headers
        Map<String, String> receivedHeaders = new HashMap<>();
        receivedHeaders.put("traceparent", "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01"); // 示例W3C Trace Context头

        ReceiverService receiver = new ReceiverService(openTelemetry);
        receiver.processRemoteCall(receivedHeaders);
    }
}