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[carriers] add env carrier #4609

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[carriers] add env carrier #4609

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60 changes: 60 additions & 0 deletions opentelemetry-api/src/opentelemetry/propagators/envcarrier.py
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Original file line number Diff line number Diff line change
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import os
import typing
from opentelemetry.propagators.textmap import Getter, Setter

class EnvironmentGetter(Getter[dict]):
"""This class decorates Getter to enable extracting from context and baggage
from environment variables.
"""

KEY_MAPPING = {
"TRACEPARENT": "traceparent",
"TRACESTATE": "tracestate",
"BAGGAGE": "baggage"
}
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@pellared pellared Jun 3, 2025 •
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Why do we have a special handling only for these 3 keys?
Couldn't 't it be a generic rule how the env carrier works?

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I've removed them and pushed the change. They were there from my working prototype enforcing on those were set. However, in the specification we do outline that those are the three well-known values that SHOULD be used. Ultimately, it doesn't matter. Any keys in the environment, when lowered, will only be considered valid context in the text map propagator when they match one of the well-known specs supported in the SDK. (b3/w3c/etc)


def __init__(self):
self.env_copy = dict(os.environ)
self.carrier = {}

for env_key, env_value in self.env_copy.items():
if env_key in self.KEY_MAPPING:
self.carrier[self.KEY_MAPPING[env_key]] = env_value
else:
self.carrier[env_key] = env_value

def get(self, carrier: dict, key: str) -> typing.Optional[typing.List[str]]:
"""Get a value from the carrier for the given key"""
val = self.carrier.get(key, None)
if val is None:
return None
if isinstance(val, typing.Iterable) and not isinstance(val, str):
return list(val)
return [val]

def keys(self, carrier: dict) -> typing.List[str]:
"""Get all keys from the carrier"""
return list(self.carrier.keys())

class EnvironmentSetter(Setter[dict]):
"""This class decorates Setter to enable setting context and baggage
to environment variables.
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@pellared pellared Jun 3, 2025 •
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Isn't the purpose to set env var for some external process that is going to be spawned?

From https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/context/env-carriers.md#environment-variable-immutability and https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/context/env-carriers.md#process-spawning:

Applications SHOULD NOT modify context-related environment variables of the environment in which the parent process exists.

Parent processes SHOULD copy the current environment variables (if applicable), modify, and inject context when spawning child processes.

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yes! and i'm not sure how best to handle that implementation detail in practice at the carrier level, which is why this is the current set.

In my head, the only real path forward I see with that portion is to set a dictionary with that new context, and let the implementer use that returned dictionary when they do a popen run like the below psuedo code:

# somehow the user sets traceparent, tracestate, and baggage and setter returns an env dictionary instead of what it does now

# the user then takes that and sets it in popen
popen.run(["something"], env=env_dict_from_setter)

"""

KEY_MAPPING = {
"TRACEPARENT": "traceparent",
"TRACESTATE": "tracestate",
"BAGGAGE": "baggage"
}

def set(self, carrier: typing.Optional[dict], key: str, value: str) -> None:
"""Set a value in the environment for the given key.

Args:
carrier: Not used for environment setter, but kept for interface compatibility
key: The key to set
value: The value to set
"""
env_key = self.KEY_MAPPING.get(key, key.upper())

os.environ[env_key] = value
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