ot_example_with_block.py

ot_example_with_block.py

# Some sort of top-level handler
def handle_purchase_async(done_callback):
    with tracer.start_active_span("purchase") as span:
        # add a marker so that it can be resumed later
        span.capture()
        # record_transaction() would return right away
        record_transaction(_finish_recording, done_callback)
        
    # Note: the Span is NOT finished here because the capture()
    # has incremented a refcounter, so exiting from the context
    # manager only reactivates the previous Span
    do_something_else()

def _finish_recording(status, span, done_callback):
    # the span reference must be passed (or get from a closure) like
    # it is in Java for the Continuation class; the Span must be reactivated
    tracer.active_span_source.make_active(span)
 
    with span:
        if status.is_error():
            span.set_tag("error", True)

    # Note: the `span` has been captured once and deactivated once in
    # this context manager, so the finish() is called automatically
    
    # Invoke the handle_purchase_async callback
    done_callback()
    
def done_callback():
    # Note: because here we don't use capture(), the Span is finished
    # immediately after exiting the context manager
    with tracer.start_active_span("db.write_result") as span:
        db_call()