fix extracting baggage and update so that baggage only context is used

ddtrace/contrib/trace_utils.py

@@ -560,14 +560,12 @@ def activate_distributed_headers(tracer, int_config=None, request_headers=None,
     """
     if override is False:
         return None
-
     if override or (int_config and distributed_tracing_enabled(int_config)):
         context = HTTPPropagator.extract(request_headers)
 
         # Only need to activate the new context if something was propagated
-        if not context.trace_id or context._baggage:
+        if not context.trace_id and not context._baggage:
             return None
-
         # Do not reactivate a context with the same trace id
         # DEV: An example could be nested web frameworks, when one layer already
         #      parsed request headers and activated them.

ddtrace/propagation/http.py

@@ -103,6 +103,7 @@ def _possible_header(header):
 _POSSIBLE_HTTP_HEADER_B3_FLAGS = _possible_header(_HTTP_HEADER_B3_FLAGS)
 _POSSIBLE_HTTP_HEADER_TRACEPARENT = _possible_header(_HTTP_HEADER_TRACEPARENT)
 _POSSIBLE_HTTP_HEADER_TRACESTATE = _possible_header(_HTTP_HEADER_TRACESTATE)
+_POSSIBLE_HTTP_BAGGAGE_HEADER = _possible_header(_HTTP_HEADER_BAGGAGE)
 
 
 # https://www.w3.org/TR/trace-context/#traceparent-header-field-values
@@ -939,7 +940,7 @@ def _inject(span_context: Context, headers: Dict[str, str]) -> None:
 
     @staticmethod
     def _extract(headers: Dict[str, str]) -> Context:
-        header_value = headers.get(_HTTP_HEADER_BAGGAGE)
+        header_value = _extract_header_value(_POSSIBLE_HTTP_BAGGAGE_HEADER, headers)
 
         if not header_value:
             return Context(baggage={})