# Copyright The 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 __future__ import annotations
import logging
import typing
from contextvars import Token
from os import environ
from uuid import uuid4
# pylint: disable=wrong-import-position
from opentelemetry.context.context import Context, _RuntimeContext # noqa
from opentelemetry.environment_variables import OTEL_PYTHON_CONTEXT
from opentelemetry.util._importlib_metadata import entry_points
logger = logging.getLogger(__name__)
def _load_runtime_context() -> _RuntimeContext:
"""Initialize the RuntimeContext
Returns:
An instance of RuntimeContext.
"""
# FIXME use a better implementation of a configuration manager
# to avoid having to get configuration values straight from
# environment variables
default_context = "contextvars_context"
configured_context = environ.get(OTEL_PYTHON_CONTEXT, default_context) # type: str
try:
return next( # type: ignore
iter( # type: ignore
entry_points( # type: ignore
group="opentelemetry_context",
name=configured_context,
)
)
).load()()
except Exception: # pylint: disable=broad-exception-caught
logger.exception(
"Failed to load context: %s, fallback to %s",
configured_context,
default_context,
)
return next( # type: ignore
iter( # type: ignore
entry_points( # type: ignore
group="opentelemetry_context",
name=default_context,
)
)
).load()()
_RUNTIME_CONTEXT = _load_runtime_context()
[docs]
def create_key(keyname: str) -> str:
"""To allow cross-cutting concern to control access to their local state,
the RuntimeContext API provides a function which takes a keyname as input,
and returns a unique key.
Args:
keyname: The key name is for debugging purposes and is not required to be unique.
Returns:
A unique string representing the newly created key.
"""
return keyname + "-" + str(uuid4())
[docs]
def get_value(key: str, context: typing.Optional[Context] = None) -> object:
"""To access the local state of a concern, the RuntimeContext API
provides a function which takes a context and a key as input,
and returns a value.
Args:
key: The key of the value to retrieve.
context: The context from which to retrieve the value, if None, the current context is used.
Returns:
The value associated with the key.
"""
return context.get(key) if context is not None else get_current().get(key)
[docs]
def set_value(
key: str, value: object, context: typing.Optional[Context] = None
) -> Context:
"""To record the local state of a cross-cutting concern, the
RuntimeContext API provides a function which takes a context, a
key, and a value as input, and returns an updated context
which contains the new value.
Args:
key: The key of the entry to set.
value: The value of the entry to set.
context: The context to copy, if None, the current context is used.
Returns:
A new `Context` containing the value set.
"""
if context is None:
context = get_current()
new_values = context.copy()
new_values[key] = value
return Context(new_values)
[docs]
def get_current() -> Context:
"""To access the context associated with program execution,
the Context API provides a function which takes no arguments
and returns a Context.
Returns:
The current `Context` object.
"""
return _RUNTIME_CONTEXT.get_current()
[docs]
def attach(context: Context) -> Token[Context]:
"""Associates a Context with the caller's current execution unit. Returns
a token that can be used to restore the previous Context.
Args:
context: The Context to set as current.
Returns:
A token that can be used with `detach` to reset the context.
"""
return _RUNTIME_CONTEXT.attach(context)
[docs]
def detach(token: Token[Context]) -> None:
"""Resets the Context associated with the caller's current execution unit
to the value it had before attaching a specified Context.
Args:
token: The Token that was returned by a previous call to attach a Context.
"""
try:
_RUNTIME_CONTEXT.detach(token)
except Exception: # pylint: disable=broad-exception-caught
logger.exception("Failed to detach context")
# FIXME This is a temporary location for the suppress instrumentation key.
# Once the decision around how to suppress instrumentation is made in the
# spec, this key should be moved accordingly.
_ON_EMIT_RECURSION_COUNT_KEY = create_key("on_emit_recursion_count")
_SUPPRESS_INSTRUMENTATION_KEY = create_key("suppress_instrumentation")
_SUPPRESS_HTTP_INSTRUMENTATION_KEY = create_key(
"suppress_http_instrumentation"
)
__all__ = [
"Context",
"attach",
"create_key",
"detach",
"get_current",
"get_value",
"set_value",
]