def is_tracing(request):
if should_not_sample_path(request):<EOL><INDENT>return False<EOL><DEDENT>elif should_not_sample_route(request):<EOL><INDENT>return False<EOL><DEDENT>elif '<STR_LIT>' in request.headers:<EOL><INDENT>return request.headers.get('<STR_LIT>') == '<STR_LIT:1>'<EOL><DEDENT>else:<EOL><INDENT>zipkin_tracing_percent = request.registry.settings.get(<EOL>'<STR_LIT>', DEFAULT_REQUEST_TRACING_PERCENT)<EOL>return should_sample_as_per_zipkin_tracing_percent(<EOL>zipkin_tracing_percent)<EOL><DEDENT>
Determine if zipkin should be tracing
    1) Check whether the current request path is blacklisted.
    2) If not, check whether the current request route is blacklisted.
    3) If not, check if specific sampled header is present in the request.
    4) If not, Use a tracing percent (default: 0.5%) to decide.

    :param request: pyramid request object

    :returns: boolean True if zipkin should be tracing