Trazabilidad en microservicios con Spring Cloud Sleuth

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   Client Span                                                Server Span
┌──────────────────┐                                       ┌──────────────────┐
│                  │                                       │                  │
│   TraceContext   │           Http Request Headers        │   TraceContext   │
│ ┌──────────────┐ │          ┌───────────────────┐        │ ┌──────────────┐ │
│ │ TraceId      │ │          │ X─B3─TraceId      │        │ │ TraceId      │ │
│ │              │ │          │                   │        │ │              │ │
│ │ ParentSpanId │ │ Extract  │ X─B3─ParentSpanId │ Inject │ │ ParentSpanId │ │
│ │              ├─┼─────────>│                   ├────────┼>│              │ │
│ │ SpanId       │ │          │ X─B3─SpanId       │        │ │ SpanId       │ │
│ │              │ │          │                   │        │ │              │ │
│ │ Sampled      │ │          │ X─B3─Sampled      │        │ │ Sampled      │ │
│ └──────────────┘ │          └───────────────────┘        │ └──────────────┘ │
│                  │                                       │                  │
└──────────────────┘                                       └──────────────────┘

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package io.github.picodotdev.blogbitix.springcloud.client;

...

@Component
public class ProxyService {

    @Autowired
    private LoadBalancerClient loadBalancer;

    @Autowired
    private Tracing tracing;

    @Autowired
    private Tracer tracer;

    @HystrixCommand(fallbackMethod = "getFallback", commandProperties = {
            @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "4"),
            @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "50"),
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "25000")
    })
    public String get() {
        ServiceInstance instance = loadBalancer.choose("proxy");
        URI uri = instance.getUri();
        String resource = String.format("%s%s", uri.toString(), "/service");
        Invocation.Builder builder = ClientBuilder.newClient().target(resource).request();

        Span span = tracer.newTrace().start();
        TraceContext.Injector<Invocation.Builder> injector = tracing.propagation().injector((Invocation.Builder carrier, String key, String value) -> { carrier.header(key, value); });
        injector.inject(span.context(), builder);
        System.out.printf("Proxy Span (traceId: %s, spanId: %s)%n", span.context().traceIdString(), span.context().spanIdString());

        return builder.get().readEntity(String.class);
    }

    private String getFallback() {
        return "Fallback";
    }
}

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package io.github.picodotdev.blogbitix.springcloud.service;

...

@RestController
public class DefaultController {

	@Autowired
	private DefaultConfiguration configuration;

	@Autowired
	private Tracing tracing;

	@Autowired
	private Tracer tracer;

	private Random random;
	private Counter counter;

	public DefaultController(MeterRegistry registry) {
		this.random = new Random();
		this.counter = Counter.builder("service.invocations").description("Total service invocations").register(registry);
	}

	@RequestMapping("/")
	public String home(HttpServletRequest request) throws Exception {
		counter.increment();

		// Timeout simulation
		//Thread.sleep(random.nextInt(2000));

		TraceContext.Extractor<HttpServletRequest> extractor = tracing.propagation().extractor((HttpServletRequest carrier, String key) -> { return carrier.getHeader(key); });
		Span span = tracer.nextSpan(extractor.extract(request));
		System.out.printf("Client Span (traceId: %s, spanId: %s)%n", span.context().traceIdString(), span.context().spanIdString());

		return String.format("Hello world (%s, %s)", request.getRequestURL(), configuration.getKey());
	}
}

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Client Span (traceId: 94fcd131178298fd, spanId: 94fcd131178298fd)
...
Service Span (traceId: 94fcd131178298fd, spanId: 6e6380e239f30917)
...
Service response: Hello world (http://archlinux:8080/, value)

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$ ./gradlew discoveryserver:run --args="--port=8761"
$ ./gradlew configserver:run --args="--port=8090"
$ ./gradlew service:run --args="--port=8080"
$ ./gradlew proxy:run --args="--port=8085"
$ ./gradlew client:run --args="--service=proxy"

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plugins {
    id 'application'
}

mainClassName = 'io.github.picodotdev.blogbitix.springcloud.client.Main'

dependencies {
    implementation platform("org.springframework.boot:spring-boot-dependencies:2.1.4.RELEASE")
    implementation platform("org.springframework.cloud:spring-cloud-dependencies:Greenwich.SR1")

    // Spring
    def excludeSpringBootStarterLogging = { exclude(group: 'org.springframework.boot', module: 'spring-boot-starter-logging') }
    compile('org.springframework.boot:spring-boot-starter', excludeSpringBootStarterLogging)
    ...
    compile('org.springframework.cloud:spring-cloud-starter-sleuth', excludeSpringBootStarterLogging)
    ...
}