Adding propagators API and b3 SDK implementation (open-telemetry#51, open-telemetry#52)

Specification: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-propagators.md.

Author: toumorokoshi

opentelemetry-api/src/opentelemetry/context/propagation/__init__.py

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+from .httptextformat import HTTPTextFormat
+from .binaryformat import BinaryFormat

opentelemetry-api/src/opentelemetry/context/propagation/binaryformat.py

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+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import abc
+import typing
+from opentelemetry.trace import SpanContext
+
+
+class BinaryFormat(abc.ABC):
+    @staticmethod
+    @abc.abstractmethod
+    def to_bytes(context: SpanContext) -> bytes:
+        pass
+
+    @staticmethod
+    @abc.abstractmethod
+    def from_bytes(byte_representation: bytes) -> typing.Optional[SpanContext]:
+        pass

opentelemetry-api/src/opentelemetry/context/propagation/httptextformat.py

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+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import abc
+import typing
+from opentelemetry.trace import SpanContext
+
+Setter = typing.Callable[[object, str, str], None]
+Getter = typing.Callable[[object, str], str]
+
+
+class HTTPTextFormat(abc.ABC):
+    """API for propagation of spans via headers.
+
+    This class provides an interface that enables extracting and injecting
+    trace state into headers of HTTP requests. Http frameworks and client
+    can integrate with HTTPTextFormat by providing the object containing the
+    headers, and a getter and setter function for the extraction and
+    injection of values, respectively.
+
+    Example::
+
+        import flask
+        import requests
+        from opentelemetry.context.propagation import HTTPTextFormat
+
+        PROPAGATOR = HTTPTextFormat()
+
+
+
+        def get_header_from_flask_request(request, key):
+            return request.headers[key]
+
+        def set_header_into_requests_request(request: requests.Request,
+                                             key: str, value: str):
+            request.headers[key] = value
+
+        def example_route():
+            span_context = PROPAGATOR.extract(
+                get_header_from_flask_request,
+                flask.request
+            )
+            request_to_downstream = requests.Request(
+                "GET", "http://httpbin.org/get"
+            )
+            PROPAGATOR.inject(
+                span_context,
+                set_header_into_requests_request,
+                request_to_downstream
+            )
+            session = requests.Session()
+            session.send(request_to_downstream.prepare())
+
+
+    .. _Propagation API Specification:
+       https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-propagators.md
+
+    Enabling this flexi
+    """
+    @abc.abstractmethod
+    def extract(self, get_from_carrier: Getter,
+                carrier: object) -> SpanContext:
+        pass
+
+    @abc.abstractmethod
+    def inject(self, context: SpanContext, set_in_carrier: Setter,
+               carrier: object):
+        pass

opentelemetry-sdk/src/opentelemetry/sdk/context/__init__.py

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+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from opentelemetry.context.propagation.httptextformat import HTTPTextFormat
+import opentelemetry.trace as trace
+
+
+class B3Format(HTTPTextFormat):
+    """Propagator for the B3 HTTP header format.
+
+    See: https://github.com/openzipkin/b3-propagation
+    """
+
+    SINGLE_HEADER_KEY = "b3"
+    TRACE_ID_KEY = "x-b3-traceid"
+    SPAN_ID_KEY = "x-b3-spanid"
+    SAMPLED_KEY = "x-b3-sampled"
+
+    @classmethod
+    def extract(cls, get_from_carrier, carrier):
+        trace_id = trace.INVALID_TRACE_ID
+        span_id = trace.INVALID_SPAN_ID
+        sampled = 1
+
+        single_header = get_from_carrier(carrier, cls.SINGLE_HEADER_KEY)
+        if single_header:
+            # b3-propagation spec calls for the sampling state to be
+            # "deferred", which is unspecified. This concept does not
+            # translate to SpanContext, so we set it as recorded.
+            sampled = "1"
+            fields = single_header.split("-", 4)
+
+            if len(fields) == 1:
+                sampled = fields[0]
+            elif len(fields) == 2:
+                trace_id, span_id = fields
+            elif len(fields) == 3:
+                trace_id, span_id, sampled = fields
+            elif len(fields) == 4:
+                trace_id, span_id, sampled, _parent_span_id = fields
+            else:
+                return trace.INVALID_SPAN_CONTEXT
+        else:
+            trace_id = get_from_carrier(carrier, cls.TRACE_ID_KEY)
+            span_id = get_from_carrier(carrier, cls.SPAN_ID_KEY)
+            sampled = get_from_carrier(carrier, cls.SAMPLED_KEY)
+
+        options = 0
+        if sampled == "1":
+            options |= trace.TraceOptions.RECORDED
+        return trace.SpanContext(
+            trace_id=int(trace_id),
+            span_id=int(span_id),
+            trace_options=options,
+            trace_state={},
+        )
+
+    @classmethod
+    def inject(cls, context, set_in_carrier, carrier):
+        sampled = (trace.TraceOptions.RECORDED & context.trace_options) != 0
+        set_in_carrier(carrier, cls.TRACE_ID_KEY, str(context.trace_id))
+        set_in_carrier(carrier, cls.SPAN_ID_KEY, str(context.span_id))
+        set_in_carrier(carrier, cls.SAMPLED_KEY, "1" if sampled else "0")

opentelemetry-sdk/src/opentelemetry/sdk/context/propagation/__init__.py

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+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+import opentelemetry.sdk.context.propagation.b3_format as b3_format
+import opentelemetry.sdk.trace as trace
+
+FORMAT = b3_format.B3Format()
+
+
+def _get_from_dict(carrier: dict, key: str) -> str:
+    return carrier.get(key)
+
+
+def _set_into_dict(carrier: dict, key: str, value: str):
+    carrier[key] = value
+
+
+class TestB3Format(unittest.TestCase):
+    def test_extract_multi_header(self):
+        """Test the extraction of B3 headers """
+        trace_id = str(trace.generate_trace_id())
+        span_id = str(trace.generate_span_id())
+        carrier = {
+            FORMAT.TRACE_ID_KEY: trace_id,
+            FORMAT.SPAN_ID_KEY: span_id,
+            FORMAT.SAMPLED_KEY: "1",
+        }
+        span_context = FORMAT.extract(_get_from_dict, carrier)
+        new_carrier = {}
+        FORMAT.inject(span_context, _set_into_dict, new_carrier)
+        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY], trace_id)
+        self.assertEqual(new_carrier[FORMAT.SPAN_ID_KEY], span_id)
+        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")
+
+    def test_extract_single_headder(self):
+        """Test the extraction from a single b3 header"""
+        trace_id = str(trace.generate_trace_id())
+        span_id = str(trace.generate_span_id())
+        carrier = {FORMAT.SINGLE_HEADER_KEY: "{}-{}".format(trace_id, span_id)}
+        span_context = FORMAT.extract(_get_from_dict, carrier)
+        new_carrier = {}
+        FORMAT.inject(span_context, _set_into_dict, new_carrier)
+        self.assertEqual(new_carrier[FORMAT.TRACE_ID_KEY], trace_id)
+        self.assertEqual(new_carrier[FORMAT.SPAN_ID_KEY], span_id)
+        self.assertEqual(new_carrier[FORMAT.SAMPLED_KEY], "1")