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Added experimental HTTP backpropagators (#1762)
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Diff for: ‎CHANGELOG.md

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@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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- Added `SpanKind` to `should_sample` parameters, suggest using parent span context's tracestate
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instead of manually passed in tracestate in `should_sample`
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([#1764](https://github.com/open-telemetry/opentelemetry-python/pull/1764))
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- Added experimental HTTP back propagators.
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([#1762](https://github.com/open-telemetry/opentelemetry-python/pull/1762))
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### Changed
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- Adjust `B3Format` propagator to be spec compliant by not modifying context

Diff for: ‎opentelemetry-instrumentation/src/opentelemetry/instrumentation/propagators.py

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# Copyright The OpenTelemetry Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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This module implements experimental propagators to inject trace context
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into response carriers. This is useful for server side frameworks that start traces
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when server requests and want to share the trace context with the client so the
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client can add it's spans to the same trace.
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This is part of an upcoming W3C spec and will eventually make it to the Otel spec.
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https://w3c.github.io/trace-context/#trace-context-http-response-headers-format
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"""
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import typing
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from abc import ABC, abstractmethod
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import opentelemetry.trace as trace
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from opentelemetry.context.context import Context
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from opentelemetry.propagators import textmap
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from opentelemetry.trace import format_span_id, format_trace_id
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_HTTP_HEADER_ACCESS_CONTROL_EXPOSE_HEADERS = "Access-Control-Expose-Headers"
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_RESPONSE_PROPAGATOR = None
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def get_global_response_propagator():
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return _RESPONSE_PROPAGATOR
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def set_global_response_propagator(propagator):
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global _RESPONSE_PROPAGATOR # pylint:disable=global-statement
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_RESPONSE_PROPAGATOR = propagator
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class Setter(ABC):
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@abstractmethod
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def set(self, carrier, key, value):
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"""Inject the provided key value pair in carrier."""
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class DictHeaderSetter(Setter):
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def set(self, carrier, key, value): # pylint: disable=no-self-use
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old_value = carrier.get(key, "")
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if old_value:
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value = "{0}, {1}".format(old_value, value)
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carrier[key] = value
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class FuncSetter(Setter):
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"""FuncSetter coverts a function into a valid Setter. Any function that can
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set values in a carrier can be converted into a Setter by using FuncSetter.
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This is useful when injecting trace context into non-dict objects such
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HTTP Response objects for different framework.
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For example, it can be used to create a setter for Falcon response object as:
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setter = FuncSetter(falcon.api.Response.append_header)
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and then used with the propagator as:
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propagator.inject(falcon_response, setter=setter)
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This would essentially make the propagator call `falcon_response.append_header(key, value)`
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"""
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def __init__(self, func):
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self._func = func
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def set(self, carrier, key, value):
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self._func(carrier, key, value)
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default_setter = DictHeaderSetter()
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class ResponsePropagator(ABC):
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@abstractmethod
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def inject(
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self,
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carrier: textmap.CarrierT,
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context: typing.Optional[Context] = None,
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setter: textmap.Setter = default_setter,
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) -> None:
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"""Injects SpanContext into the HTTP response carrier."""
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class TraceResponsePropagator(ResponsePropagator):
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"""Experimental propagator that injects tracecontext into HTTP responses."""
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def inject(
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self,
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carrier: textmap.CarrierT,
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context: typing.Optional[Context] = None,
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setter: textmap.Setter = default_setter,
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) -> None:
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"""Injects SpanContext into the HTTP response carrier."""
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span = trace.get_current_span(context)
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span_context = span.get_span_context()
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if span_context == trace.INVALID_SPAN_CONTEXT:
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return
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header_name = "traceresponse"
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setter.set(
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carrier,
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header_name,
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"00-{trace_id}-{span_id}-{:02x}".format(
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span_context.trace_flags,
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trace_id=format_trace_id(span_context.trace_id),
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span_id=format_span_id(span_context.span_id),
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),
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)
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setter.set(
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carrier,
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_HTTP_HEADER_ACCESS_CONTROL_EXPOSE_HEADERS,
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header_name,
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)

Diff for: ‎opentelemetry-instrumentation/tests/test_propagators.py

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# Copyright The OpenTelemetry Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# pylint: disable=protected-access
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from opentelemetry import trace
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from opentelemetry.instrumentation import propagators
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from opentelemetry.instrumentation.propagators import (
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DictHeaderSetter,
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TraceResponsePropagator,
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get_global_response_propagator,
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set_global_response_propagator,
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)
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from opentelemetry.test.test_base import TestBase
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class TestGlobals(TestBase):
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def test_get_set(self):
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original = propagators._RESPONSE_PROPAGATOR
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propagators._RESPONSE_PROPAGATOR = None
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self.assertIsNone(get_global_response_propagator())
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prop = TraceResponsePropagator()
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set_global_response_propagator(prop)
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self.assertIs(prop, get_global_response_propagator())
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propagators._RESPONSE_PROPAGATOR = original
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class TestDictHeaderSetter(TestBase):
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def test_simple(self):
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setter = DictHeaderSetter()
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carrier = {}
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setter.set(carrier, "kk", "vv")
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self.assertIn("kk", carrier)
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self.assertEqual(carrier["kk"], "vv")
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def test_append(self):
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setter = DictHeaderSetter()
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carrier = {"kk": "old"}
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setter.set(carrier, "kk", "vv")
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self.assertIn("kk", carrier)
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self.assertEqual(carrier["kk"], "old, vv")
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class TestTraceResponsePropagator(TestBase):
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def test_inject(self):
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span = trace.NonRecordingSpan(
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trace.SpanContext(
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trace_id=1,
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span_id=2,
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is_remote=False,
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trace_flags=trace.DEFAULT_TRACE_OPTIONS,
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trace_state=trace.DEFAULT_TRACE_STATE,
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),
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)
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ctx = trace.set_span_in_context(span)
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prop = TraceResponsePropagator()
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carrier = {}
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prop.inject(carrier, ctx)
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self.assertEqual(
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carrier["Access-Control-Expose-Headers"], "traceresponse"
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)
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self.assertEqual(
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carrier["traceresponse"],
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"00-00000000000000000000000000000001-0000000000000002-00",
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)

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