not able to get parent span, send from Client service to Server service

[mayur-more]

I am new to OpenTelemetry word. I have created spans for my services separately, but when i am try to combine spans of two different services, using context propogation, I am not able to do it successfully. I have used following code:

`// at client side:
public static void sendContext(String resource) {

TextMapSetter setter =
new TextMapSetter() {
@OverRide
public void set(HttpURLConnection carrier, String key, String value) {
carrier.setRequestProperty(key, value);
}
};
HttpURLConnection transportLayer = null;
String urlString = "http://127.0.0.1:8080" + resource;
try {
URL url = new URL(urlString);
transportLayer = (HttpURLConnection) url.openConnection();
} catch (MalformedURLException ex) {
System.out.println(ex.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}
GlobalOpenTelemetry.getPropagators()
.getTextMapPropagator()
.inject(Context.current(), transportLayer, setter);
}

// at server side:
public static Context getContext(HttpServletRequest request) {

TextMapGetter getter =
new TextMapGetter() {
@OverRide
public String get(HttpServletRequest carrier, String key) {
Enumeration headerNames = carrier.getHeaderNames();
if (headerNames != null) {
while (headerNames.hasMoreElements()) {
String headerName = headerNames.nextElement();
System.out.println("headerNames.nextElement(): " + headerName);
if (headerName.equals(key)) {
String headerValue = request.getHeader(headerName);
System.out.println("headerValue): " + headerValue);
return headerValue;
}
}
}

    return null;
  }

  @Override
  public Iterable<String> keys(HttpServletRequest carrier) {
    Set<String> set = new HashSet<String>();
    Enumeration<String> headerNames = carrier.getHeaderNames();
    if (headerNames != null) {
      while (headerNames.hasMoreElements()) {
        set.add(headerNames.nextElement());
      }
    }
    return set;
  }
};

Context extractedContext =
GlobalOpenTelemetry.getPropagators()
.getTextMapPropagator()
.extract(Context.current(), request, getter);
}`

At server, i am not able to get parent span. Kindly help on this.

[jkwatson]

How have you configured your OpenTelemetry instances on client and server? Have you looked at the examples in this repository?

[mayur-more]

Following is my code for client and server services for auto-instrumentation:
I have added two modules(client and server) under opentelemetry-java-instrumentation/instrumentation/
This is code before i have added code for context propagation.
Client Advice class:
public static class ClientAdvice {
@Advice.OnMethodEnter
public static void onEnter(
@Advice.Origin String origin,
@Advice.Local("otelContext") Context context,
@Advice.Local("otelScope") Scope scope) {

  String subStr = origin.substring(0, origin.indexOf("(") + 1);
  String operation = subStr.substring(subStr.lastIndexOf(".") + 1, subStr.indexOf("("));
  
  OpenTelemetry openTelemetry = SdkConfiguration.initOpenTelemetry();
  Tracer tracer = openTelemetry.getTracer("test");
  Span span = tracer.spanBuilder("/" + operation).setSpanKind(SpanKind.CLIENT).startSpan();
  scope = span.makeCurrent();

  if (span != null) {
    span.setAttribute("method_name", origin);
  }
}

@Advice.OnMethodExit
public static void onExit(
    @Advice.Origin String origin,
    @Advice.Local("otelContext") Context context,
    @Advice.Local("otelScope") Scope scope) {
  
  Span span = Span.current();
  scope = span.makeCurrent();
  scope.close();
  span.end();
}

}

Server Advice class:
public static class CidsAdvice {
@Advice.OnMethodEnter
public static void onEnter(@Advice.Origin String origin) {

  String subStr = origin.substring(0, origin.indexOf("(") + 1);
  String operation = subStr.substring(subStr.lastIndexOf(".") + 1, subStr.indexOf("("));

  Tracer tracer = GlobalOpenTelemetry.getTracer("test");
  Span span = tracer.spanBuilder("/" + operation).startSpan();
  Scope scope = span.makeCurrent();

  if (span != null) {
    span.setAttribute("method_name", origin);
  }
}

@Advice.OnMethodExit
public static void onExit(@Advice.Origin String origin) {
  
  Span span = Span.current();
  Scope scope = span.makeCurrent();
  scope.close();
  span.end();
}

}

[jkwatson]

If you're in the agent, you must not configure your own copy of the SDK. If you need assistance writing agent instrumentation please open a discussion in the open-telemetry/opentelemetry-java-instrumentation repository.

[mayur-more]

Thanks. I have created one: open-telemetry/opentelemetry-java-instrumentation#3128

[hkdev27]

Context injector class:
@OverRide
public UserBillingAddress getUserBillingAddress(long id) {

	  Span child = tracer.spanBuilder("user-billing-address-service").setSpanKind(SpanKind.CLIENT).startSpan();
	  child.addEvent("User billing address with id-service",Instant.EPOCH);
	  child.setAttribute(TRACE_ID,child.getSpanContext().getTraceId());
	  MDC.put(TRACE_ID,child.getSpanContext().getTraceId());
	 
	log.info("User billing address with id: {}", id);
	try(Scope scope = child.makeCurrent()) {
		
		TextMapSetter<HttpURLConnection> setter =
				  new TextMapSetter<HttpURLConnection>() {
				    @Override
				    public void set(HttpURLConnection carrier, String key, String value) {
				        carrier.setRequestProperty(key, value);
				    }
				};
				URL url = new URL("http://localhost:8081/address");
		TextMapPropagator textMapPropagator = W3CTraceContextPropagator.getInstance();
		HttpURLConnection  httpURLConnection = (HttpURLConnection) url.openConnection();
	     textMapPropagator.inject(Context.current(), httpURLConnection, setter);
		Optional<UserEntity> entity = userRepository.findById(id);
		if(entity.isPresent()) {
			Address address = addressServiceProxy.findById(id);
			User user = convertToDto(entity.get());
			return new UserBillingAddress(user.getId(), user.getName(), address);
		}
		  }catch(Exception exception) { 
			  log.error("Address Service is down"); 
			  }finally
		  { child.end(); }
		 
	return null;
}

Context extractor class:

TextMapPropagator textMapPropagator = W3CTraceContextPropagator.getInstance();

	TextMapGetter<HttpServletRequest> getter =
			  new TextMapGetter<HttpServletRequest>() {
			    @Override
			    public String get(HttpServletRequest carrier, String key) {
			      if (StringUtils.isNoneEmpty(carrier.getHeader(key))) {
			        return carrier.getHeader(key);
			      }
			      return null;
			    }

				@Override
				public Iterable<String> keys(HttpServletRequest carrier) {
					return null;
				}
			};

	   // Extract and store the propagated span's SpanContext and other available concerns
	   // in the specified Context.
	   Context context = textMapPropagator.extract(Context.current(), request, getter);

I'm getting null for request, wherever I am seeing extract is used as follows but for me HttpExchange is not visible( compilation error)

TextMapGetter getter =
new TextMapGetter<>() {
@OverRide
public String get(HttpExchange carrier, String key) {
if (carrier.getRequestHeaders().containsKey(key)) {
return carrier.getRequestHeaders().get(key).get(0);
}
return null;
}

@OverRide
public Iterable keys(HttpExchange carrier) {
return carrier.getRequestHeaders().keySet();
}
};

Can you help me out.

[jkwatson]

It looks like your code is expecting an HttpServletRequest carrier, not an HttpExchange. Make sure you're using the same framework in both parts of your code.