Correct remote parent sampling logic

Author: hmstepanek

newrelic/api/transaction.py

@@ -285,7 +285,7 @@ def __init__(self, application, enabled=None, source=None):
         self.tracestate = ""
         self._priority = None
         self._sampled = None
-        self._traceparent_sampled = None
+        self._remote_parent_sampled = None
 
         self._distributed_trace_state = 0
 
@@ -1008,6 +1008,10 @@ def user_attributes(self):
         return create_attributes(self._custom_params, DST_ALL, self.attribute_filter)
 
     def sampling_algo_compute_sampled_and_priority(self):
+        # self._priority and self._sampled are set when parsing the W3C tracestate
+        # or newrelic DT headers and  may be overridden in _compute_sampled_and_priority
+        # based on the configuration. The only time they are set in here is when the
+        # sampling decision must be made by the adaptive sampling algorithm.
         if self._priority is None:
             # Truncate priority field to 6 digits past the decimal.
             self._priority = float(f"{random.random():.6f}")  # noqa: S311
@@ -1017,12 +1021,12 @@ def sampling_algo_compute_sampled_and_priority(self):
                 self._priority += 1
 
     def _compute_sampled_and_priority(self):
-        if self._traceparent_sampled is None:
+        if self._remote_parent_sampled is None:
             config = "default"  # Use sampling algo.
-        elif self._traceparent_sampled:
+        elif self._remote_parent_sampled:
             setting_path = "distributed_tracing.sampler.remote_parent_sampled"
             config = self.settings.distributed_tracing.sampler.remote_parent_sampled
-        else:  # self._traceparent_sampled is False.
+        else:  # self._remote_parent_sampled is False.
             setting_path = "distributed_tracing.sampler.remote_parent_not_sampled"
             config = self.settings.distributed_tracing.sampler.remote_parent_not_sampled
 
@@ -1033,7 +1037,7 @@ def _compute_sampled_and_priority(self):
             self._sampled = False
             self._priority = 0
         else:
-            if config != "default":
+            if config not in ("default", "adaptive"):
                 _logger.warning("%s=%s is not a recognized value. Using 'default' instead.", setting_path, config)
             self.sampling_algo_compute_sampled_and_priority()
 
@@ -1258,10 +1262,9 @@ def _accept_distributed_trace_data(self, data, transport_type):
 
         self._trace_id = data.get("tr")
 
-        priority = data.get("pr")
-        if priority is not None:
-            self._priority = priority
-            self._sampled = data.get("sa")
+        self._priority = data.get("pr")
+        self._sampled = data.get("sa")
+        self._remote_parent_sampled = data.get("sa")
 
         if "ti" in data:
             transport_start = data["ti"] / 1000.0
@@ -1330,13 +1333,13 @@ def accept_distributed_trace_headers(self, headers, transport_type="HTTP"):
                             tracestate_data = None
                         if tracestate_data:
                             self.trusted_parent_span = tracestate_data.pop("id", None)
+                            # TODO: Make sure this doesn't override the sampled flag.
                             data.update(tracestate_data)
                         else:
                             self._record_supportability("Supportability/TraceContext/TraceState/InvalidNrEntry")
                     else:
                         self._record_supportability("Supportability/TraceContext/TraceState/NoNrEntry")
 
-            self._traceparent_sampled = data.get("sa")
             self._accept_distributed_trace_data(data, transport_type)
             self._record_supportability("Supportability/TraceContext/Accept/Success")
             return True