126 lines
4.0 KiB
Python
126 lines
4.0 KiB
Python
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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 its 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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from opentelemetry import 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 = f"{old_value}, {value}"
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carrier[key] = value
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class FuncSetter(Setter):
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"""FuncSetter converts a function into a valid Setter. Any function that
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can set values in a carrier can be converted into a Setter by using
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FuncSetter. This is useful when injecting trace context into non-dict
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objects such HTTP Response objects for different framework.
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For example, it can be used to create a setter for Falcon response object
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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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f"00-{format_trace_id(span_context.trace_id)}-{format_span_id(span_context.span_id)}-{span_context.trace_flags:02x}",
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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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)
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