Change tracing to use Resource.to_json()

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.12.0rc1-0.31b0...HEAD)
 
+- Change tracing to use `Resource.to_json()`
+  ([#2784](https://github.com/open-telemetry/opentelemetry-python/pull/2784))
 - Add min/max fields to Histogram
   ([#2759](https://github.com/open-telemetry/opentelemetry-python/pull/2759))
 - `opentelemetry-exporter-otlp-proto-http` Add support for OTLP/HTTP log exporter

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

@@ -492,7 +492,7 @@ def to_json(self, indent=4):
         f_span["attributes"] = self._format_attributes(self._attributes)
         f_span["events"] = self._format_events(self._events)
         f_span["links"] = self._format_links(self._links)
-        f_span["resource"] = self._format_attributes(self._resource.attributes)
+        f_span["resource"] = self._format_resource(self._resource)
 
         return json.dumps(f_span, indent=indent)
 
@@ -533,6 +533,11 @@ def _format_links(links):
             f_links.append(f_link)
         return f_links
 
+    @staticmethod
+    def _format_resource(resource):
+        resource_json_obj = json.loads(resource.to_json())
+        return {k: v for k, v in resource_json_obj.items() if v}
+
 
 class SpanLimits:
     """The limits that should be enforce on recorded data such as events, links, attributes etc.