OTEL_PROPAGATORS refinements (#995)

open-telemetry · Sep 25, 2020 · 4982756 · 4982756
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -88,6 +88,9 @@ Updates:
   ([#984](https://github.com/open-telemetry/opentelemetry-specification/pull/984)
 - Metrics SDK: Specify TBD default aggregation for ValueRecorder
   ([#984](https://github.com/open-telemetry/opentelemetry-specification/pull/984)
+- SDK: Specify known values, as well as basic error handling for OTEL_PROPAGATORS.
+  ([#962](https://github.com/open-telemetry/opentelemetry-specification/pull/962))
+  ([#995](https://github.com/open-telemetry/opentelemetry-specification/pull/995))
 
 ## v0.6.0 (07-01-2020)
 

diff --git a/specification/sdk-environment-variables.md b/specification/sdk-environment-variables.md
@@ -8,9 +8,10 @@ The goal of this specification is to unify the environment variable names betwee
 | ------------------------ | ------------------------------------------------- | --------------------------------- | ----------------------------------- |
 | OTEL_RESOURCE_ATTRIBUTES | Key-value pairs to be used as resource attributes |                                   | See [Resource SDK](./resource/sdk.md#specifying-resource-information-via-an-environment-variable) for more details. |
 | OTEL_LOG_LEVEL           | Log level used by the SDK logger                  | "info"                            |                                     |
-| OTEL_PROPAGATORS         | Propagators to be used as a comma separated list  | "tracecontext,baggage" |                                     |
+| OTEL_PROPAGATORS         | Propagators to be used as a comma separated list  | "tracecontext,baggage"            | Values MUST be deduplicated in order to register a `Propagator` only once. Unrecognized values MUST generate a warning and be gracefully ignored. |
 
-Known values for OTEL_PROPAGATORS are: "tracecontext", "baggage", "b3", "jaeger"
+Known values for OTEL_PROPAGATORS are: "tracecontext", "baggage", "b3", "jaeger".
+Additional values can be specified in the respective SDK's documentation, in case third party `Propagator`s are supported, such as "xray" or "ottracer".
 
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