chore(propagation): only call extract once per request for flask and django

ddtrace/_trace/trace_handlers.py

@@ -106,14 +106,18 @@ def _get_parameters_for_new_span_directly_from_context(ctx: core.ExecutionContex
     return span_kwargs
 
 
-def _start_span(ctx: core.ExecutionContext, call_trace: bool = True, **kwargs) -> "Span":
+def _start_span(ctx: core.ExecutionContext, call_trace: bool = True, activate_distributed_headers, **kwargs) -> "Span":
     span_kwargs = _get_parameters_for_new_span_directly_from_context(ctx)
     call_trace = ctx.get_item("call_trace", call_trace)
     tracer = (ctx.get_item("middleware") or ctx["pin"]).tracer
-    distributed_headers_config = ctx.get_item("distributed_headers_config")
-    if distributed_headers_config:
+    import pdb; pdb.set_trace()
+    # this returns ddtrace.settings.integration.IntegrationConfig, we should change the naming to reflect this
+    #  from distributed_headers_config  to integration_config. Need to do this for calls of method too
+    integration_config = ctx.get_item("distributed_headers_config")
+    activate_distributed_headers = ctx.get_item("activate_distributed_headers")
+    if integration_config and activate_distributed_headers:
         trace_utils.activate_distributed_headers(
-            tracer, int_config=distributed_headers_config, request_headers=ctx["distributed_headers"]
+            tracer, int_config=integration_config, request_headers=ctx["distributed_headers"]
         )
     distributed_context = ctx.get_item("distributed_context")
     if distributed_context and not call_trace:

ddtrace/contrib/internal/flask/patch.py

@@ -532,6 +532,7 @@ def _patched_request(pin, wrapped, instance, args, kwargs):
             block_request_callable=_block_request_callable,
             ignored_exception_type=NotFound,
             tags={COMPONENT: config.flask.integration_name},
+            activate_distributed_headers=True,
         ) as ctx, ctx.span:
             core.dispatch("flask._patched_request", (ctx,))
             return wrapped(*args, **kwargs)

ddtrace/contrib/internal/wsgi/wsgi.py

@@ -95,6 +95,9 @@ def __call__(self, environ: Iterable, start_response: Callable) -> wrapt.ObjectP
         headers = get_request_headers(environ)
         closing_iterable = ()
         not_blocked = True
+        # this would be the fix, we'd basically just add a kwarg activate_distributed_headers, and then
+        # when we call _start_span in core, we check if it's set to true or not, if it's not 
+        # (for every non local root span) we don't call activate_distributed_headers
         with core.context_with_data(
             "wsgi.__call__",
             remote_addr=environ.get("REMOTE_ADDR"),
@@ -104,8 +107,9 @@ def __call__(self, environ: Iterable, start_response: Callable) -> wrapt.ObjectP
             span_type=SpanTypes.WEB,
             span_name=(self._request_call_name if hasattr(self, "_request_call_name") else self._request_span_name),
             middleware_config=self._config,
-            distributed_headers_config=self._config,
+            integration_config=self._config,
             distributed_headers=environ,
+            activate_distributed_headers=True,
             environ=environ,
             middleware=self,
             span_key="req_span",

ddtrace/contrib/trace_utils.py

@@ -576,7 +576,9 @@ def activate_distributed_headers(tracer, int_config=None, request_headers=None,
         #
         #     app = Flask(__name__)  # Traced via Flask instrumentation
         #     app = DDWSGIMiddleware(app)  # Extra layer on top for WSGI
+        # this is what's saving us from resetting context over and over again
         current_context = tracer.current_trace_context()
+        # we'll error here because we don't have a trace_id etc.
         if current_context and current_context.trace_id == context.trace_id:
             log.debug(
                 "will not activate extracted Context(trace_id=%r, span_id=%r), a context with that trace id is already active",  # noqa: E501

ddtrace/internal/core/__init__.py

@@ -175,7 +175,9 @@ def __init__(
     def __enter__(self) -> "ExecutionContext":
         if self._span is None and "_CURRENT_CONTEXT" in globals():
             self._token: contextvars.Token["ExecutionContext"] = _CURRENT_CONTEXT.set(self)
+            # context.started.flask._patched_request
         dispatch("context.started.%s" % self.identifier, (self,))
+        # context.started.start_span.flask._patched_request
         dispatch("context.started.start_span.%s" % self.identifier, (self,))
         return self