Use environment variables for tracer and meter providers (#1571)

Author: ocelotl

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v0.17b0...HEAD)
 
+### Changed
+- Tracer and Meter provider environment variables are now consistent with the rest
+  ([#1571](https://github.com/open-telemetry/opentelemetry-python/pull/1571)])
+
 ### Added
 - Added `end_on_exit` argument to `start_as_current_span`
   ([#1519](https://github.com/open-telemetry/opentelemetry-python/pull/1519)])

opentelemetry-api/src/opentelemetry/environment_variables/__init__.py

@@ -19,3 +19,5 @@
 OTEL_PYTHON_SERVICE_NAME = "OTEL_PYTHON_SERVICE_NAME"
 OTEL_TRACE_EXPORTER = "OTEL_TRACE_EXPORTER"
 OTEL_METRICS_EXPORTER = "OTEL_METRICS_EXPORTER"
+OTEL_PYTHON_TRACER_PROVIDER = "OTEL_PYTHON_TRACER_PROVIDER"
+OTEL_PYTHON_METER_PROVIDER = "OTEL_PYTHON_METER_PROVIDER"

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

@@ -19,6 +19,11 @@
 
 from pkg_resources import iter_entry_points
 
+from opentelemetry.environment_variables import (
+    OTEL_PYTHON_METER_PROVIDER,
+    OTEL_PYTHON_TRACER_PROVIDER,
+)
+
 if TYPE_CHECKING:
     from opentelemetry.metrics import MeterProvider
     from opentelemetry.trace import TracerProvider
@@ -39,15 +44,18 @@ def time_ns() -> int:
         return int(time.time() * 1e9)
 
 
-def _load_provider(provider: str) -> Provider:
+def _load_provider(
+    provider_environment_variable: str, provider: str
+) -> Provider:
     try:
         entry_point = next(
             iter_entry_points(
                 "opentelemetry_{}".format(provider),
                 name=cast(
                     str,
                     environ.get(
-                        provider.upper(), "default_{}".format(provider),
+                        provider_environment_variable,
+                        "default_{}".format(provider),
                     ),
                 ),
             )
@@ -59,8 +67,13 @@ def _load_provider(provider: str) -> Provider:
 
 
 def _load_meter_provider(provider: str) -> "MeterProvider":
-    return cast("MeterProvider", _load_provider(provider))
+    return cast(
+        "MeterProvider", _load_provider(OTEL_PYTHON_METER_PROVIDER, provider),
+    )
 
 
 def _load_trace_provider(provider: str) -> "TracerProvider":
-    return cast("TracerProvider", _load_provider(provider))
+    return cast(
+        "TracerProvider",
+        _load_provider(OTEL_PYTHON_TRACER_PROVIDER, provider),
+    )