Baggage propagation

[rmbamds]

I have a Spring Boot application where I need to call operationA.process() and operationB.process() sequentially. When I set baggage in OperationA, I do not see the changes in OperationB.

OperationA: Added 'param1' to the baggage.
OperationB: Retrieved 'param1' from the baggage, but the value is null.

@RestController
public class RollController {
    @GetMapping("/demo")
    public String demo() {

        OperationA operationA = new OperationA();
        OperationB operationB = new OperationB();

        try (Scope scope = Context.current().makeCurrent()) {
            operationA.process();
            operationB.process();
        }
        return "Completed";

    }
}

public class OperationA {

    public void process() {

        Baggage updatedBaggage = Baggage.current().toBuilder()
                .put("param1", "value1")
                .build();

        Context updatedContext = Context.current().with(updatedBaggage);

        try (Scope scope = updatedContext.makeCurrent()) {
            System.out.println("OperationA: Added 'param1' to baggage.");
        }
    }
}

public class OperationB {
    public void process() {
        // Attempt to retrieve the baggage
        Baggage currentBaggage = Baggage.current();
        String value = currentBaggage.getEntryValue("param1");
        System.out.println("OperationB: Retrieved 'param1' from baggage with value: " + value);
    }
}

[jkwatson]

Your "operationB" isn't being run inside the scope that's created with the baggage in it, so you won't see it there. operationA doesn't propagate the context with the baggage in it in any way that would be accessible to operationB. Trace through the call stacks by hand and you'll see what I mean.