Getting invalid SpanContext in mongo extension for java OpenTelemetry automatic instrumentation - open-telemetry

Question

I am writing an extension of OpenTelemetry to input traceId as comment in mongo query. For this I have put an Advice on the find method in com.mongodb.client.MongoCollection. Inside the Advice when I call spanContext.isValid() it returns false, also spanId and traceId have all zeros in them.
MongoQueryInstrumentation.java
public class MongoQueryInstrumentation implements TypeInstrumentation {
#Override
public ElementMatcher<TypeDescription> typeMatcher() {
return implementsInterface(named("com.mongodb.client.MongoCollection"));
}
public void transform(TypeTransformer transformer) {
transformer.applyAdviceToMethod(
named("find").and(takesArgument(0, Bson.class)).and(ElementMatchers.isPublic()),
AdvicesFind.class.getName());
}
#SuppressWarnings("unused")
public static class AdvicesFind {
#Advice.OnMethodExit(suppress = Throwable.class)
public static void onExit(#Advice.Return(readOnly = false) FindIterable<?> result) {
SpanContext spanContext = Java8BytecodeBridge.currentSpan().getSpanContext();
System.out.println("traceId:" + spanContext.getTraceId());
System.out.println("VALID :" + spanContext.isValid());
result.comment(spanContext.getTraceId());
}
}
}
MongoInstrumentationModule.java
#AutoService(InstrumentationModule.class)
public final class MongoInstrumentationModule extends InstrumentationModule {
public MongoInstrumentationModule() {
super("mongo-ext", "mongo-4.0");
}
#Override
public int order() {
return 1;
}
#Override
public ElementMatcher.Junction<ClassLoader> classLoaderMatcher() {
return hasClassesNamed("com.mongodb.internal.async.SingleResultCallback");
}
#Override
public List<TypeInstrumentation> typeInstrumentations() {
return Collections.singletonList(new MongoQueryInstrumentation());
}
}
OUTPUT:
traceId:00000000000000000000000000000000
VALID :false
I am exporting the logs to zipkin, there db.statement is
{"find": "sampleCollection", "filter": {"title": "MongoDB"}, "comment": "00000000000000000000000000000000", "$db": "myDb", "lsid": {"id": {"$binary": {"base64": "nOpqMCwHRWe2h+qmVEgGIQ==", "subType": "04"}}}}
I tried doing similar thing in JDBC by adding a comment containing traceId and spanId and there it worked as expected. There I patched sendQueryString method of NativeProtocolInstrumentation.
There Java8BytecodeBridge.currentSpan().getSpanContext() returned a valid spanId but in mongo it does not.