ext/opentracing-shim: implement inject and extract (#256)

This commit implements inject() and extract() support for TEXT_MAP and
HTTP_HEADERS formats by using the configured OpenTelemetry propagators.

The support for binary propagators is not completed on opentelemetry-python so
this commit does not include for such format.

Author: mauriciovasquezbernal

ext/opentelemetry-ext-opentracing-shim/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Implement extract and inject support for HTTP_HEADERS and TEXT_MAP formats.
+
 ## 0.2a0
 
 Released 2019-10-29

ext/opentelemetry-ext-opentracing-shim/src/opentelemetry/ext/opentracing_shim/__init__.py

@@ -17,6 +17,7 @@
 import opentracing
 from deprecated import deprecated
 
+from opentelemetry import propagators
 from opentelemetry.ext.opentracing_shim import util
 
 logger = logging.getLogger(__name__)
@@ -184,6 +185,10 @@ class TracerShim(opentracing.Tracer):
     def __init__(self, tracer):
         super().__init__(scope_manager=ScopeManagerShim(self))
         self._otel_tracer = tracer
+        self._supported_formats = (
+            opentracing.Format.TEXT_MAP,
+            opentracing.Format.HTTP_HEADERS,
+        )
 
     def unwrap(self):
         """Returns the wrapped OpenTelemetry `Tracer` object."""
@@ -249,16 +254,32 @@ def start_span(
 
     def inject(self, span_context, format, carrier):
         # pylint: disable=redefined-builtin
-        logger.warning(
-            "Calling unimplemented method inject() on class %s",
-            self.__class__.__name__,
+        # This implementation does not perform the injecting by itself but
+        # uses the configured propagators in opentelemetry.propagators.
+        # TODO: Support Format.BINARY once it is supported in
+        # opentelemetry-python.
+        if format not in self._supported_formats:
+            raise opentracing.UnsupportedFormatException
+
+        propagator = propagators.get_global_httptextformat()
+        propagator.inject(
+            span_context.unwrap(), type(carrier).__setitem__, carrier
         )
-        # TODO: Implement.
 
     def extract(self, format, carrier):
         # pylint: disable=redefined-builtin
-        logger.warning(
-            "Calling unimplemented method extract() on class %s",
-            self.__class__.__name__,
-        )
-        # TODO: Implement.
+        # This implementation does not perform the extracing by itself but
+        # uses the configured propagators in opentelemetry.propagators.
+        # TODO: Support Format.BINARY once it is supported in
+        # opentelemetry-python.
+        if format not in self._supported_formats:
+            raise opentracing.UnsupportedFormatException
+
+        def get_as_list(dict_object, key):
+            value = dict_object.get(key)
+            return [value] if value is not None else []
+
+        propagator = propagators.get_global_httptextformat()
+        otel_context = propagator.extract(get_as_list, carrier)
+
+        return SpanContextShim(otel_context)

ext/opentelemetry-ext-opentracing-shim/tests/test_shim.py

@@ -18,7 +18,8 @@
 import opentracing
 
 import opentelemetry.ext.opentracing_shim as opentracingshim
-from opentelemetry import trace
+from opentelemetry import propagators, trace
+from opentelemetry.context.propagation.httptextformat import HTTPTextFormat
 from opentelemetry.ext.opentracing_shim import util
 from opentelemetry.sdk.trace import Tracer
 
@@ -40,6 +41,17 @@ def setUpClass(cls):
 
         trace.set_preferred_tracer_implementation(lambda T: Tracer())
 
+        # Save current propagator to be restored on teardown.
+        cls._previous_propagator = propagators.get_global_httptextformat()
+
+        # Set mock propagator for testing.
+        propagators.set_global_httptextformat(MockHTTPTextFormat)
+
+    @classmethod
+    def tearDownClass(cls):
+        # Restore previous propagator.
+        propagators.set_global_httptextformat(cls._previous_propagator)
+
     def test_shim_type(self):
         # Verify shim is an OpenTracing tracer.
         self.assertIsInstance(self.shim, opentracing.Tracer)
@@ -453,3 +465,91 @@ def test_span_on_error(self):
         self.assertEqual(
             scope.span.unwrap().events[0].attributes["error.kind"], Exception
         )
+
+    def test_inject_http_headers(self):
+        """Test `inject()` method for Format.HTTP_HEADERS."""
+
+        otel_context = trace.SpanContext(trace_id=1220, span_id=7478)
+        context = opentracingshim.SpanContextShim(otel_context)
+
+        headers = {}
+        self.shim.inject(context, opentracing.Format.HTTP_HEADERS, headers)
+        self.assertEqual(headers[MockHTTPTextFormat.TRACE_ID_KEY], str(1220))
+        self.assertEqual(headers[MockHTTPTextFormat.SPAN_ID_KEY], str(7478))
+
+    def test_inject_text_map(self):
+        """Test `inject()` method for Format.TEXT_MAP."""
+
+        otel_context = trace.SpanContext(trace_id=1220, span_id=7478)
+        context = opentracingshim.SpanContextShim(otel_context)
+
+        # Verify Format.TEXT_MAP
+        text_map = {}
+        self.shim.inject(context, opentracing.Format.TEXT_MAP, text_map)
+        self.assertEqual(text_map[MockHTTPTextFormat.TRACE_ID_KEY], str(1220))
+        self.assertEqual(text_map[MockHTTPTextFormat.SPAN_ID_KEY], str(7478))
+
+    def test_inject_binary(self):
+        """Test `inject()` method for Format.BINARY."""
+
+        otel_context = trace.SpanContext(trace_id=1220, span_id=7478)
+        context = opentracingshim.SpanContextShim(otel_context)
+
+        # Verify exception for non supported binary format.
+        with self.assertRaises(opentracing.UnsupportedFormatException):
+            self.shim.inject(context, opentracing.Format.BINARY, bytearray())
+
+    def test_extract_http_headers(self):
+        """Test `extract()` method for Format.HTTP_HEADERS."""
+
+        carrier = {
+            MockHTTPTextFormat.TRACE_ID_KEY: 1220,
+            MockHTTPTextFormat.SPAN_ID_KEY: 7478,
+        }
+
+        ctx = self.shim.extract(opentracing.Format.HTTP_HEADERS, carrier)
+        self.assertEqual(ctx.unwrap().trace_id, 1220)
+        self.assertEqual(ctx.unwrap().span_id, 7478)
+
+    def test_extract_text_map(self):
+        """Test `extract()` method for Format.TEXT_MAP."""
+
+        carrier = {
+            MockHTTPTextFormat.TRACE_ID_KEY: 1220,
+            MockHTTPTextFormat.SPAN_ID_KEY: 7478,
+        }
+
+        ctx = self.shim.extract(opentracing.Format.TEXT_MAP, carrier)
+        self.assertEqual(ctx.unwrap().trace_id, 1220)
+        self.assertEqual(ctx.unwrap().span_id, 7478)
+
+    def test_extract_binary(self):
+        """Test `extract()` method for Format.BINARY."""
+
+        # Verify exception for non supported binary format.
+        with self.assertRaises(opentracing.UnsupportedFormatException):
+            self.shim.extract(opentracing.Format.BINARY, bytearray())
+
+
+class MockHTTPTextFormat(HTTPTextFormat):
+    """Mock propagator for testing purposes."""
+
+    TRACE_ID_KEY = "mock-traceid"
+    SPAN_ID_KEY = "mock-spanid"
+
+    @classmethod
+    def extract(cls, get_from_carrier, carrier):
+        trace_id_list = get_from_carrier(carrier, cls.TRACE_ID_KEY)
+        span_id_list = get_from_carrier(carrier, cls.SPAN_ID_KEY)
+
+        if not trace_id_list or not span_id_list:
+            return trace.INVALID_SPAN_CONTEXT
+
+        return trace.SpanContext(
+            trace_id=int(trace_id_list[0]), span_id=int(span_id_list[0])
+        )
+
+    @classmethod
+    def inject(cls, context, set_in_carrier, carrier):
+        set_in_carrier(carrier, cls.TRACE_ID_KEY, str(context.trace_id))
+        set_in_carrier(carrier, cls.SPAN_ID_KEY, str(context.span_id))