From 2c3f4e29980e3e0e97d70553444545d91a5a3b75 Mon Sep 17 00:00:00 2001
From: Diego Hurtado <ocelotl@users.noreply.github.com>
Date: Wed, 16 Sep 2020 11:03:34 -0600
Subject: [PATCH] Add support for OTEL_PROPAGATORS

Fixes #1058
---
 opentelemetry-api/setup.cfg                   |  3 ++
 .../src/opentelemetry/propagators/__init__.py | 31 ++++++++++++++-----
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/opentelemetry-api/setup.cfg b/opentelemetry-api/setup.cfg
index 9435d92f197..4ad44c64519 100644
--- a/opentelemetry-api/setup.cfg
+++ b/opentelemetry-api/setup.cfg
@@ -55,6 +55,9 @@ opentelemetry_meter_provider =
     default_meter_provider = opentelemetry.metrics:DefaultMeterProvider
 opentelemetry_tracer_provider =
     default_tracer_provider = opentelemetry.trace:DefaultTracerProvider
+opentelemetry_propagator =
+    tracecontext = opentelemetry.trace.propagation.tracecontext:TraceContextTextMapPropagator
+    baggage = opentelemetry.baggage.propagation:BaggagePropagator
 
 [options.extras_require]
 test =
diff --git a/opentelemetry-api/src/opentelemetry/propagators/__init__.py b/opentelemetry-api/src/opentelemetry/propagators/__init__.py
index f34e3c588b4..5f8e9a26e69 100644
--- a/opentelemetry-api/src/opentelemetry/propagators/__init__.py
+++ b/opentelemetry-api/src/opentelemetry/propagators/__init__.py
@@ -53,15 +53,16 @@ def example_route():
     https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-propagators.md
 """
 
+from pkg_resources import iter_entry_points
+from logging import getLogger
 import typing
 
-from opentelemetry.baggage.propagation import BaggagePropagator
 from opentelemetry.context.context import Context
 from opentelemetry.propagators import composite
 from opentelemetry.trace.propagation import textmap
-from opentelemetry.trace.propagation.tracecontext import (
-    TraceContextTextMapPropagator,
-)
+from opentelemetry.configuration import Configuration
+
+logger = getLogger(__name__)
 
 
 def extract(
@@ -104,9 +105,25 @@ def inject(
     get_global_textmap().inject(set_in_carrier, carrier, context)
 
 
-_HTTP_TEXT_FORMAT = composite.CompositeHTTPPropagator(
-    [TraceContextTextMapPropagator(), BaggagePropagator()],
-)  # type: textmap.TextMapPropagator
+try:
+
+    propagators = []
+
+    for propagator in Configuration().get(
+        "PROPAGATORS", "tracecontext,baggage"
+    ).split(","):
+
+        propagators.append(
+            next(
+                iter_entry_points("opentelemetry_propagator", propagator)
+            ).load()()
+        )
+
+except Exception:  # pylint: disable=broad-except
+    logger.exception("Failed to load configured propagators")
+    raise
+
+_HTTP_TEXT_FORMAT = composite.CompositeHTTPPropagator(propagators)
 
 
 def get_global_textmap() -> textmap.TextMapPropagator: