What Does This Do

Keeps the Java HTTP client context available across all asynchronous response-body callbacks.

The body subscriber previously used a one-shot continuation. The first callback resolved it, so later callbacks could run without the expected context and the trace could be reported before response processing
completed.

The continuation is now held until a terminal event:

• onComplete
• onError
• subscription cancellation

A shared terminal guard ensures concurrent or repeated terminal signals release it exactly once.

sequenceDiagram
    participant Client as HTTP client
    participant Wrapper as BodySubscriber wrapper
    participant Context as Trace continuation
    participant Delegate as Body subscriber

    Client->>Wrapper: onSubscribe(subscription)
    Wrapper->>Delegate: onSubscribe(wrapped subscription)

    loop Response chunks
        Client->>Wrapper: onNext(chunk)
        Wrapper->>Context: resume()
        Wrapper->>Delegate: onNext(chunk)
        Wrapper->>Context: close resumed scope
    end

    alt Response completes
        Client->>Wrapper: onComplete()
        Wrapper->>Context: resume()
        Wrapper->>Delegate: onComplete()
        Wrapper->>Context: release once
    else Response fails
        Client->>Wrapper: onError(error)
        Wrapper->>Context: resume()
        Wrapper->>Delegate: onError(error)
        Wrapper->>Context: release once
    else Subscription is cancelled
        Delegate->>Wrapper: cancel()
        Wrapper->>Client: delegate cancel()
        Wrapper->>Context: release once
    end

Motivation

Java HTTP response bodies can invoke onNext multiple times. Their tracing context must remain available until body processing actually terminates, including cancellation.

Additional Notes

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: [PROJ-IDENT]