java -javaagent:../opentelemetry-javaagent/opentelemetry-javaagent.jar \
-Dotel.traces.exporter=otlp \
-Dotel.exporter.otlp.endpoint=http://192.168.91.11:4317 \
-Dotel.resource.attributes=service.name=demo,version=dev \
-Dotel.metrics.exporter=otlp \
-jar springboot-opentelemetry-otlp-server.jar --client=true

	<dependencies>
		...
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-exporter-otlp</artifactId>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-extension-annotations</artifactId>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-semconv</artifactId>
            <version>1.21.0-alpha</version>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-sdk-extension-autoconfigure</artifactId>
            <version>1.21.0-alpha</version>
        </dependency>
		...
	</dependencies>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>io.opentelemetry</groupId>
				<artifactId>opentelemetry-bom</artifactId>
				<version>1.21.0</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

/**
 * @Description 推薦使用這種方式。<br>
 * 這種方式的背后提供的是 noop，也就是默認(rèn)的 provider，會(huì)根據(jù)啟動(dòng)參數(shù)來(lái)決定自行構(gòu)造 所需的 provider。
 * @return io.opentelemetry.api.OpenTelemetry
 **/
@Bean
public OpenTelemetry openTelemetry() {
    return AutoConfiguredOpenTelemetrySdk.builder()
            .setResultAsGlobal(false) // 這里填寫(xiě)false，否則會(huì)與全局javaagent 沖突
            .build()
            .getOpenTelemetrySdk();
}

TracerProvider getTracerProvider();

    @Bean
    public Tracer tracer() {
        return openTelemetry().getTracer(appName);
    }

Span span = tracer.spanBuilder(spanName).startSpan();

Span span = Span.current();

span.setAttribute(key, value);

Span child = tracer.spanBuilder(spanName)
		.addLink(span(1))
		.addLink(span(2))
		.addLink(span(3))
		.startSpan();

span.addEvent(eventName);
span.addEvent(eventName,Attributes);

void parent() {
	Span parentSpan = tracer.spanBuilder("parent")
		.startSpan();
	childSpan(parentSpan);
	parentSpan.end();
}
void childSpan(Span parentSpan) {
	Span childSpan = tracer.spanBuilder("childSpan")
		.setParent(parentSpan)
		.startSpan();
	// do stuff
	childSpan.end();
}

// Baggage 用法,此處set
	Baggage.current().toBuilder().put("app.username", "gateway").build().makeCurrent();
	logger.info("gateway set baggage[app.username] value: gateway");

 // Baggage 用法,此get
	String baggage = Baggage.current().getEntryValue("app.username");
	logger.info("resource get baggage[app.username] value: {}", baggage);

tracer.spanBuilder(spanName).setParent(context)

SpanContext create(String traceIdHex, String spanIdHex, TraceFlags traceFlags, TraceState traceState)

private Context withSpanContext(SpanContext spanContext, Context context) {
	return context.with(Span.wrap(spanContext));
}

    /***
     * @Description 通過(guò)已知的traceId和spanId,來(lái)構(gòu)造一個(gè)新span。
     * @Param [spanName, traceId, spanId]
     * @return java.lang.String
     **/
    @GetMapping("/customSpanByTraceIdAndSpanId")
    @ResponseBody
    public String customSpanByTraceIdAndSpanId(String spanName,String traceId,String spanId){
        assert StringUtils.isEmpty(spanName):"spanName 不能為空";
        assert StringUtils.isEmpty(traceId):"traceId 不能為空";
        assert StringUtils.isEmpty(spanId):"spanId 不能為空";
        Context context =
                withSpanContext(
                        SpanContext.create(
                                traceId, spanId, TraceFlags.getSampled(), TraceState.getDefault()),
                        Context.current());
        Span span = tracer.spanBuilder(spanName)
                .setParent(context)
                .startSpan();
        span.setAttribute("attribute.a2", "some value");
        span.setAttribute("func","attr");
        span.setAttribute("app","otel3");
        span.end();
        return buildTraceUrl(span.getSpanContext().getTraceId());
    }
    private Context withSpanContext(SpanContext spanContext, Context context) {
        return context.with(Span.wrap(spanContext));
    }

    @Bean
    public Meter meter() {
        return openTelemetry().getMeter(appName);
    }

    default MeterProvider getMeterProvider() {
        return MeterProvider.noop();
    }

	meter().gaugeBuilder("connections")
		.setDescription("當(dāng)前Socket.io連接數(shù)")
		.setUnit("1")
		.buildWithCallback(
				result -> {
					System.out.println("metrics");
					for (int i = 1; i < 4; i++) {
						result.record(
								i,
								Attributes.of(
										AttributeKey.stringKey("id"),
										"a" + i));
					}
				});