Handle mixed case cloud propagator headers (#112)

* Handle mixed case cloud propagator headers

* update CHANGELOG

Author: aabmass

docs-requirements.txt

@@ -3,5 +3,5 @@ Sphinx
 sphinx-autodoc-typehints
 opentelemetry-api
 opentelemetry-sdk
-./opentelemetry-exporter-google-cloud
-./opentelemetry-tools-google-cloud
+-e ./opentelemetry-exporter-google-cloud
+-e ./opentelemetry-tools-google-cloud

opentelemetry-tools-google-cloud/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- Handle mixed case cloud propagator headers
+  ([#112](https://github.com/GoogleCloudPlatform/opentelemetry-operations-python/pull/112))
+
 ## Version 0.17b0
 
 Released 2021-02-04

opentelemetry-tools-google-cloud/src/opentelemetry/tools/cloud_trace_propagator.py

@@ -25,7 +25,7 @@
     get_hexadecimal_trace_id,
 )
 
-_TRACE_CONTEXT_HEADER_NAME = "X-Cloud-Trace-Context"
+_TRACE_CONTEXT_HEADER_NAME = "x-cloud-trace-context"
 _TRACE_CONTEXT_HEADER_FORMAT = r"(?P<trace_id>[0-9a-f]{32})\/(?P<span_id>[\d]{1,20});o=(?P<trace_flags>\d+)"
 _TRACE_CONTEXT_HEADER_RE = re.compile(_TRACE_CONTEXT_HEADER_FORMAT)
 _FIELDS = {_TRACE_CONTEXT_HEADER_NAME}
@@ -37,18 +37,36 @@ class CloudTraceFormatPropagator(textmap.TextMapPropagator):
     Cloud format.
     """
 
+    @staticmethod
+    def _get_header_value(
+        getter: textmap.Getter[textmap.TextMapPropagatorT],
+        carrier: textmap.TextMapPropagatorT,
+    ) -> typing.Optional[str]:
+        # first try all lowercase header
+        header = getter.get(carrier, _TRACE_CONTEXT_HEADER_NAME)
+        if header:
+            return header[0]
+
+        # otherwise try to find in keys for mixed case
+        for key in getter.keys(carrier):
+            if key.lower() == _TRACE_CONTEXT_HEADER_NAME:
+                header = getter.get(carrier, key)
+                if header:
+                    return header[0]
+        return None
+
     def extract(
         self,
         getter: textmap.Getter[textmap.TextMapPropagatorT],
         carrier: textmap.TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
-        header = getter.get(carrier, _TRACE_CONTEXT_HEADER_NAME)
+        header = self._get_header_value(getter, carrier)
 
         if not header:
             return trace.set_span_in_context(trace.INVALID_SPAN, context)
 
-        match = re.fullmatch(_TRACE_CONTEXT_HEADER_RE, header[0])
+        match = re.fullmatch(_TRACE_CONTEXT_HEADER_RE, header)
         if match is None:
             return trace.set_span_in_context(trace.INVALID_SPAN, context)
 

opentelemetry-tools-google-cloud/tests/test_cloud_trace_propagator.py

@@ -105,6 +105,26 @@ def test_valid_header(self):
         self.assertEqual(new_span_context.trace_flags, TraceFlags(0))
         self.assertTrue(new_span_context.is_remote)
 
+    def test_mixed_case_header_key(self):
+        header_value = "{}/{};o=1".format(
+            get_hexadecimal_trace_id(self.valid_trace_id), self.valid_span_id
+        )
+
+        for header_key in (
+            "X-Cloud-Trace-Context",
+            "X-ClOuD-tRace-ConTeXt",
+            "X-CLOUD-TRACE-CONTEXT",
+        ):
+            header_map = {header_key: [header_value]}
+            new_context = self.propagator.extract(dict_getter, header_map)
+            new_span_context = trace.get_current_span(
+                new_context
+            ).get_span_context()
+            self.assertEqual(new_span_context.trace_id, self.valid_trace_id)
+            self.assertEqual(new_span_context.span_id, self.valid_span_id)
+            self.assertEqual(new_span_context.trace_flags, TraceFlags(1))
+            self.assertTrue(new_span_context.is_remote)
+
     def test_invalid_header_format(self):
         header = "invalid_header"
         self.assertEqual(