Fixed circular dependency that can happen when injecting custom samplers

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fixed circular dependency issue with custom samplers
+  ([#3026](https://github.com/open-telemetry/opentelemetry-python/pull/3026))
+
 ## Version 1.14.0/0.35b0 (2022-11-04)
 
 - Add logarithm and exponent mappings

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

@@ -21,8 +21,9 @@
 import os
 from abc import ABC, abstractmethod
 from os import environ
-from typing import Dict, Optional, Sequence, Tuple, Type
+from typing import Dict, Optional, Sequence, Tuple, Type, Callable
 
+from pkg_resources import iter_entry_points
 from typing_extensions import Literal
 
 from opentelemetry.environment_variables import (
@@ -31,6 +32,10 @@
     OTEL_PYTHON_ID_GENERATOR,
     OTEL_TRACES_EXPORTER,
 )
+from opentelemetry.sdk.environment_variables import (
+    OTEL_TRACES_SAMPLER,
+    OTEL_TRACES_SAMPLER_ARG,
+)
 from opentelemetry.metrics import set_meter_provider
 from opentelemetry.sdk._logs import (
     LoggerProvider,
@@ -54,9 +59,9 @@
 from opentelemetry.sdk.trace import TracerProvider
 from opentelemetry.sdk.trace.export import BatchSpanProcessor, SpanExporter
 from opentelemetry.sdk.trace.id_generator import IdGenerator
-from opentelemetry.sdk.util import _import_config_components
 from opentelemetry.semconv.resource import ResourceAttributes
 from opentelemetry.trace import set_tracer_provider
+from opentelemetry.sdk.trace.sampling import Sampler
 
 _EXPORTER_OTLP = "otlp"
 _EXPORTER_OTLP_PROTO_GRPC = "otlp_proto_grpc"
@@ -82,9 +87,35 @@
 _RANDOM_ID_GENERATOR = "random"
 _DEFAULT_ID_GENERATOR = _RANDOM_ID_GENERATOR
 
+_OTEL_SAMPLER_ENTRY_POINT_GROUP = "opentelemetry_traces_sampler"
+
 _logger = logging.getLogger(__name__)
 
 
+def _import_config_components(
+    selected_components, entry_point_name
+) -> Sequence[Tuple[str, object]]:
+    component_entry_points = {
+        ep.name: ep for ep in iter_entry_points(entry_point_name)
+    }
+    component_impls = []
+    for selected_component in selected_components:
+        entry_point = component_entry_points.get(selected_component, None)
+        if not entry_point:
+            raise RuntimeError(
+                f"Requested component '{selected_component}' not found in entry points for '{entry_point_name}'"
+            )
+
+        component_impl = entry_point.load()
+        component_impls.append((selected_component, component_impl))
+
+    return component_impls
+
+
+def _get_sampler() -> str:
+    return environ.get(OTEL_TRACES_SAMPLER, None)
+
+
 def _get_id_generator() -> str:
     return environ.get(OTEL_PYTHON_ID_GENERATOR, _DEFAULT_ID_GENERATOR)
 
@@ -149,7 +180,8 @@ def _get_exporter_names(
 
 def _init_tracing(
     exporters: Dict[str, Type[SpanExporter]],
-    id_generator: IdGenerator,
+    id_generator: IdGenerator = None,
+    sampler: Sampler = None,
     auto_instrumentation_version: Optional[str] = None,
 ):
     # if env var OTEL_RESOURCE_ATTRIBUTES is given, it will read the service_name
@@ -161,7 +193,8 @@ def _init_tracing(
             ResourceAttributes.TELEMETRY_AUTO_VERSION
         ] = auto_instrumentation_version
     provider = TracerProvider(
-        id_generator=id_generator(),
+        id_generator=id_generator,
+        sampler=sampler,
         resource=Resource.create(auto_resource),
     )
     set_tracer_provider(provider)
@@ -266,13 +299,43 @@ def _import_exporters(
     return trace_exporters, metric_exporters, log_exporters
 
 
+
+
+
+def _import_sampler_factory(sampler_name: str) -> Callable[[str], Sampler]:
+    _, sampler_impl = _import_config_components(
+        [sampler_name.strip()], _OTEL_SAMPLER_ENTRY_POINT_GROUP
+    )[0]
+    return sampler_impl
+
+
+def _import_sampler(sampler_name: str) -> Sampler:
+    if not sampler_name:
+        return None
+    try:
+        sampler_factory = _import_sampler_factory(sampler_name)
+        sampler_arg = os.getenv(OTEL_TRACES_SAMPLER_ARG, "")
+        sampler = sampler_factory(sampler_arg)
+        if not isinstance(sampler, Sampler):
+            message = f"Traces sampler factory, {sampler_factory}, produced output, {sampler}, which is not a Sampler object."
+            _logger.warning(message)
+            raise ValueError(message)
+        return sampler
+    except Exception as exc:  # pylint: disable=broad-except
+        _logger.warning(
+            "Using default sampler. Failed to initialize custom sampler, %s: %s",
+            sampler_name,
+            exc,
+        )
+        return None
+
 def _import_id_generator(id_generator_name: str) -> IdGenerator:
     id_generator_name, id_generator_impl = _import_config_components(
         [id_generator_name.strip()], "opentelemetry_id_generator"
     )[0]
 
     if issubclass(id_generator_impl, IdGenerator):
-        return id_generator_impl
+        return id_generator_impl()
 
     raise RuntimeError(f"{id_generator_name} is not an IdGenerator")
 
@@ -283,9 +346,11 @@ def _initialize_components(auto_instrumentation_version):
         _get_exporter_names("metrics"),
         _get_exporter_names("logs"),
     )
+    sampler_name = _get_sampler()
+    sampler = _import_sampler(sampler_name) if sampler_name else None
     id_generator_name = _get_id_generator()
     id_generator = _import_id_generator(id_generator_name)
-    _init_tracing(trace_exporters, id_generator, auto_instrumentation_version)
+    _init_tracing(exporters=trace_exporters, id_generator=id_generator, sampler=sampler, auto_instrumentation_version=auto_instrumentation_version)
     _init_metrics(metric_exporters, auto_instrumentation_version)
     logging_enabled = os.getenv(
         _OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED, "false"

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

@@ -78,9 +78,6 @@
 
 _ENV_VALUE_UNSET = ""
 
-# pylint: disable=protected-access
-_TRACE_SAMPLER = sampling._get_from_env_or_default()
-
 
 class SpanProcessor:
     """Interface which allows hooks for SDK's `Span` start and end method
@@ -1115,7 +1112,7 @@ class TracerProvider(trace_api.TracerProvider):
 
     def __init__(
         self,
-        sampler: sampling.Sampler = _TRACE_SAMPLER,
+        sampler: sampling.Sampler = None,
         resource: Resource = Resource.create({}),
         shutdown_on_exit: bool = True,
         active_span_processor: Union[
@@ -1132,6 +1129,8 @@ def __init__(
         else:
             self.id_generator = id_generator
         self._resource = resource
+        if not sampler:
+            sampler = sampling._get_from_env_or_default()
         self.sampler = sampler
         self._span_limits = span_limits or SpanLimits()
         self._atexit_handler = None

opentelemetry-sdk/src/opentelemetry/sdk/trace/sampling.py

@@ -73,7 +73,8 @@
     * parentbased_always_off - Sampler that respects its parent span's sampling decision, but otherwise never samples.
     * parentbased_traceidratio - Sampler that respects its parent span's sampling decision, but otherwise samples probabalistically based on rate.
 
-Sampling probability can be set with ``OTEL_TRACES_SAMPLER_ARG`` if the sampler is traceidratio or parentbased_traceidratio. Rate must be in the range [0.0,1.0]. When not provided rate will be set to 1.0 (maximum rate possible).
+Sampling probability can be set with ``OTEL_TRACES_SAMPLER_ARG`` if the sampler is traceidratio or parentbased_traceidratio. Rate must be in the range [0.0,1.0]. When not provided rate will be set to
+1.0 (maximum rate possible).
 
 Prev example but with environment variables. Please make sure to set the env ``OTEL_TRACES_SAMPLER=traceidratio`` and ``OTEL_TRACES_SAMPLER_ARG=0.001``.
 
@@ -97,9 +98,10 @@
     with trace.get_tracer(__name__).start_as_current_span("Test Span"):
         ...
 
-In order to create a configurable custom sampler, create an entry point for the custom sampler factory method under the entry point group, ``opentelemetry_traces_sampler``. The custom sampler factory
-method must be of type ``Callable[[str], Sampler]``, taking a single string argument and returning a Sampler object. The single input will come from the string value of the
-``OTEL_TRACES_SAMPLER_ARG`` environment variable. If ``OTEL_TRACES_SAMPLER_ARG`` is not configured, the input will be an empty string. For example:
+When utilizing a configurator, you can configure a custom sampler. In order to create a configurable custom sampler, create an entry point for the custom sampler
+factory method or function under the entry point group, ``opentelemetry_traces_sampler``. The custom sampler factory method must be of type ``Callable[[str], Sampler]``, taking a single string argument and
+returning a Sampler object. The single input will come from the string value of the ``OTEL_TRACES_SAMPLER_ARG`` environment variable. If ``OTEL_TRACES_SAMPLER_ARG`` is not configured, the input will
+be an empty string. For example:
 
 .. code:: python
 
@@ -134,18 +136,18 @@ class CustomSamplerFactory:
 import os
 from logging import getLogger
 from types import MappingProxyType
-from typing import Callable, Optional, Sequence
+from typing import Optional, Sequence
 
 # pylint: disable=unused-import
 from opentelemetry.context import Context
 from opentelemetry.sdk.environment_variables import (
     OTEL_TRACES_SAMPLER,
     OTEL_TRACES_SAMPLER_ARG,
 )
-from opentelemetry.sdk.util import _import_config_components
 from opentelemetry.trace import Link, SpanKind, get_current_span
 from opentelemetry.trace.span import TraceState
 from opentelemetry.util.types import Attributes
+import traceback
 
 _logger = getLogger(__name__)
 
@@ -193,9 +195,6 @@ def __init__(
         self.trace_state = trace_state
 
 
-_OTEL_SAMPLER_ENTRY_POINT_GROUP = "opentelemetry_traces_sampler"
-
-
 class Sampler(abc.ABC):
     @abc.abstractmethod
     def should_sample(
@@ -407,48 +406,26 @@ def __init__(self, rate: float):
 
 
 def _get_from_env_or_default() -> Sampler:
-    traces_sampler_name = os.getenv(
+    trace_sampler = os.getenv(
         OTEL_TRACES_SAMPLER, "parentbased_always_on"
     ).lower()
+    if trace_sampler not in _KNOWN_SAMPLERS:
+        _logger.warning("Couldn't recognize sampler %s.", trace_sampler)
+        trace_sampler = "parentbased_always_on"
 
-    if traces_sampler_name in _KNOWN_SAMPLERS:
-        if traces_sampler_name in ("traceidratio", "parentbased_traceidratio"):
-            try:
-                rate = float(os.getenv(OTEL_TRACES_SAMPLER_ARG))
-            except ValueError:
-                _logger.warning(
-                    "Could not convert TRACES_SAMPLER_ARG to float."
-                )
-                rate = 1.0
-            return _KNOWN_SAMPLERS[traces_sampler_name](rate)
-        return _KNOWN_SAMPLERS[traces_sampler_name]
-    try:
-        traces_sampler_factory = _import_sampler_factory(traces_sampler_name)
-        sampler_arg = os.getenv(OTEL_TRACES_SAMPLER_ARG, "")
-        traces_sampler = traces_sampler_factory(sampler_arg)
-        if not isinstance(traces_sampler, Sampler):
-            message = f"Traces sampler factory, {traces_sampler_factory}, produced output, {traces_sampler}, which is not a Sampler object."
-            _logger.warning(message)
-            raise ValueError(message)
-        return traces_sampler
-    except Exception as exc:  # pylint: disable=broad-except
-        _logger.warning(
-            "Using default sampler. Failed to initialize custom sampler, %s: %s",
-            traces_sampler_name,
-            exc,
-        )
-        return _KNOWN_SAMPLERS["parentbased_always_on"]
+    if trace_sampler in ("traceidratio", "parentbased_traceidratio"):
+        try:
+            rate = float(os.getenv(OTEL_TRACES_SAMPLER_ARG))
+        except ValueError:
+            _logger.warning("Could not convert TRACES_SAMPLER_ARG to float.")
+            rate = 1.0
+        return _KNOWN_SAMPLERS[trace_sampler](rate)
+
+    return _KNOWN_SAMPLERS[trace_sampler]
 
 
 def _get_parent_trace_state(parent_context) -> Optional["TraceState"]:
     parent_span_context = get_current_span(parent_context).get_span_context()
     if parent_span_context is None or not parent_span_context.is_valid:
         return None
     return parent_span_context.trace_state
-
-
-def _import_sampler_factory(sampler_name: str) -> Callable[[str], Sampler]:
-    _, sampler_impl = _import_config_components(
-        [sampler_name.strip()], _OTEL_SAMPLER_ENTRY_POINT_GROUP
-    )[0]
-    return sampler_impl

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

@@ -14,11 +14,11 @@
 
 import datetime
 import threading
-from collections import OrderedDict, abc, deque
-from typing import List, Optional, Sequence, Tuple
+from collections import OrderedDict, deque
+from collections.abc import MutableMapping, Sequence
+from typing import Optional
 
 from deprecated import deprecated
-from pkg_resources import iter_entry_points
 
 
 def ns_to_iso_str(nanoseconds):
@@ -41,27 +41,7 @@ def get_dict_as_key(labels):
     )
 
 
-def _import_config_components(
-    selected_components: List[str], entry_point_name: str
-) -> Sequence[Tuple[str, object]]:
-    component_entry_points = {
-        ep.name: ep for ep in iter_entry_points(entry_point_name)
-    }
-    component_impls = []
-    for selected_component in selected_components:
-        entry_point = component_entry_points.get(selected_component, None)
-        if not entry_point:
-            raise RuntimeError(
-                f"Requested component '{selected_component}' not found in entry points for '{entry_point_name}'"
-            )
-
-        component_impl = entry_point.load()
-        component_impls.append((selected_component, component_impl))
-
-    return component_impls
-
-
-class BoundedList(abc.Sequence):
+class BoundedList(Sequence):
     """An append only list with a fixed max size.
 
     Calls to `append` and `extend` will drop the oldest elements if there is
@@ -112,7 +92,7 @@ def from_seq(cls, maxlen, seq):
 
 
 @deprecated(version="1.4.0")  # type: ignore
-class BoundedDict(abc.MutableMapping):
+class BoundedDict(MutableMapping):
     """An ordered dict with a fixed max capacity.
 
     Oldest elements are dropped when the dict is full and a new element is