Fix falcon usage of Span Status

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix falcon instrumentation's usage of Span Status to only set the description if the status code is ERROR.
+  ([#1840](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1840))
 - Instrument all httpx versions >= 0.18. ([#1748](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1748))
 
 ## Version 1.18.0/0.39b0 (2023-05-10)
@@ -23,9 +25,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1778](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1778))
 - Add `excluded_urls` functionality to `urllib` and `urllib3` instrumentations
   ([#1733](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1733))
-- Make Django request span attributes available for `start_span`. 
+- Make Django request span attributes available for `start_span`.
   ([#1730](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1730))
-- Make ASGI request span attributes available for `start_span`. 
+- Make ASGI request span attributes available for `start_span`.
   ([#1762](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1762))
 - `opentelemetry-instrumentation-celery` Add support for anonymous tasks.
   ([#1407](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1407))

instrumentation/opentelemetry-instrumentation-falcon/src/opentelemetry/instrumentation/falcon/__init__.py

@@ -208,7 +208,7 @@ def response_hook(span, req, resp):
 from opentelemetry.metrics import get_meter
 from opentelemetry.semconv.metrics import MetricInstruments
 from opentelemetry.semconv.trace import SpanAttributes
-from opentelemetry.trace.status import Status
+from opentelemetry.trace.status import Status, StatusCode
 from opentelemetry.util.http import get_excluded_urls, get_traced_request_attrs
 
 _logger = getLogger(__name__)
@@ -461,11 +461,17 @@ def process_response(
         try:
             status_code = int(status)
             span.set_attribute(SpanAttributes.HTTP_STATUS_CODE, status_code)
+            otel_status_code = http_status_to_status_code(
+                status_code, server_span=True
+            )
+
+            # set the description only when the status code is ERROR
+            if otel_status_code is not StatusCode.ERROR:
+                reason = None
+
             span.set_status(
                 Status(
-                    status_code=http_status_to_status_code(
-                        status_code, server_span=True
-                    ),
+                    status_code=otel_status_code,
                     description=reason,
                 )
             )