Add support for B3 parentspanid

Fixes #236

Author: ocelotl

Diff for: opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/b3_format.py

@@ -27,6 +27,7 @@ class B3Format(HTTPTextFormat):
     SINGLE_HEADER_KEY = "b3"
     TRACE_ID_KEY = "x-b3-traceid"
     SPAN_ID_KEY = "x-b3-spanid"
+    PARENT_SPAN_ID_KEY = "x-b3-parentspanid"
     SAMPLED_KEY = "x-b3-sampled"
     FLAGS_KEY = "x-b3-flags"
     _SAMPLE_PROPAGATE_VALUES = set(["1", "True", "true", "d"])
@@ -35,6 +36,7 @@ class B3Format(HTTPTextFormat):
     def extract(cls, get_from_carrier, carrier):
         trace_id = format_trace_id(trace.INVALID_TRACE_ID)
         span_id = format_span_id(trace.INVALID_SPAN_ID)
+        parent_span_id = format_span_id(trace.INVALID_SPAN_ID)
         sampled = "0"
         flags = None
 
@@ -55,7 +57,7 @@ def extract(cls, get_from_carrier, carrier):
             elif len(fields) == 3:
                 trace_id, span_id, sampled = fields
             elif len(fields) == 4:
-                trace_id, span_id, sampled, _parent_span_id = fields
+                trace_id, span_id, sampled, parent_span_id = fields
             else:
                 return trace.INVALID_SPAN_CONTEXT
         else:
@@ -71,6 +73,12 @@ def extract(cls, get_from_carrier, carrier):
                 )
                 or span_id
             )
+            parent_span_id = (
+                _extract_first_element(
+                    get_from_carrier(carrier, cls.PARENT_SPAN_ID_KEY)
+                )
+                or parent_span_id
+            )
             sampled = (
                 _extract_first_element(
                     get_from_carrier(carrier, cls.SAMPLED_KEY)
@@ -91,12 +99,22 @@ def extract(cls, get_from_carrier, carrier):
         # header is set to allow.
         if sampled in cls._SAMPLE_PROPAGATE_VALUES or flags == "1":
             options |= trace.TraceOptions.SAMPLED
+
+        trace_state = trace.TraceState()
+
+        if parent_span_id != trace.INVALID_SPAN_ID:
+            # FIXME This is a workaround for the error specified below being
+            # raised because of a pylint issue. Remove this when the issue is
+            # fixed in pylint.
+            # pylint: disable=E1137
+            trace_state[cls.PARENT_SPAN_ID_KEY] = int(parent_span_id, 16)
+
         return trace.SpanContext(
             # trace an span ids are encoded in hex, so must be converted
             trace_id=int(trace_id, 16),
             span_id=int(span_id, 16),
             trace_options=trace.TraceOptions(options),
-            trace_state=trace.TraceState(),
+            trace_state=trace_state,
         )
 
     @classmethod
@@ -108,6 +126,11 @@ def inject(cls, context, set_in_carrier, carrier):
         set_in_carrier(
             carrier, cls.SPAN_ID_KEY, format_span_id(context.span_id)
         )
+        set_in_carrier(
+            carrier,
+            cls.PARENT_SPAN_ID_KEY,
+            format_span_id(context.trace_state[cls.PARENT_SPAN_ID_KEY]),
+        )
         set_in_carrier(carrier, cls.SAMPLED_KEY, "1" if sampled else "0")
 
 

Diff for: opentelemetry-sdk/tests/context/propagation/test_b3_format.py

@@ -35,12 +35,16 @@ def setUpClass(cls):
         cls.serialized_span_id = b3_format.format_span_id(
             trace.generate_span_id()
         )
+        cls.serialized_parent_span_id = b3_format.format_span_id(
+            trace.generate_span_id()
+        )
 
     def test_extract_multi_header(self):
         """Test the extraction of B3 headers."""
         carrier = {
             FORMAT.TRACE_ID_KEY: self.serialized_trace_id,
             FORMAT.SPAN_ID_KEY: self.serialized_span_id,
+            FORMAT.PARENT_SPAN_ID_KEY: self.serialized_parent_span_id,
             FORMAT.SAMPLED_KEY: "1",
         }
         span_context = FORMAT.extract(get_as_list, carrier)
@@ -52,6 +56,10 @@ def test_extract_multi_header(self):
         self.assertEqual(
             new_carrier[FORMAT.SPAN_ID_KEY], self.serialized_span_id
         )
+        self.assertEqual(
+            new_carrier[FORMAT.PARENT_SPAN_ID_KEY],
+            self.serialized_parent_span_id,
+        )
         self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
 
     def test_extract_single_header(self):
@@ -72,6 +80,28 @@ def test_extract_single_header(self):
         )
         self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
 
+        carrier = {
+            FORMAT.SINGLE_HEADER_KEY: "{}-{}-1-{}".format(
+                self.serialized_trace_id,
+                self.serialized_span_id,
+                self.serialized_parent_span_id,
+            )
+        }
+        span_context = FORMAT.extract(get_as_list, carrier)
+        new_carrier = {}
+        FORMAT.inject(span_context, dict.__setitem__, new_carrier)
+        self.assertEqual(
+            new_carrier[FORMAT.TRACE_ID_KEY], self.serialized_trace_id
+        )
+        self.assertEqual(
+            new_carrier[FORMAT.SPAN_ID_KEY], self.serialized_span_id
+        )
+        self.assertEqual(
+            new_carrier[FORMAT.PARENT_SPAN_ID_KEY],
+            self.serialized_parent_span_id,
+        )
+        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+
     def test_extract_header_precedence(self):
         """A single b3 header should take precedence over multiple
         headers.

Diff for: tox.ini

@@ -21,6 +21,7 @@ python =
 [testenv]
 deps =
   test: pytest
+  ipdb
   coverage: pytest-cov
   mypy,mypyinstalled: mypy~=0.740
 
@@ -70,7 +71,7 @@ commands_pre =
   mypyinstalled: pip install file://{toxinidir}/opentelemetry-api/
 
 commands =
-  test: pytest
+  test: pytest {posargs}
   coverage: {toxinidir}/scripts/coverage.sh
 
   mypy: mypy --namespace-packages opentelemetry-api/src/opentelemetry/