Fix requests_active leak when response close raises

lib/falcon/body/request_finished.rb

@@ -11,8 +11,9 @@ module Body
 		# Wraps a response body and decrements a metric after the body is closed.
 		#
 		# Runs close on the underlying body first (which invokes rack.response_finished),
-		# then decrements the metric. Use this so requests_active stays elevated until
-		# the request is fully finished (including response_finished callbacks).
+		# then decrements the metric, even if closing raises. Use this so requests_active
+		# stays elevated until the request is fully finished (including response_finished
+		# callbacks), without leaking if close reports an error.
 		class RequestFinished < Protocol::HTTP::Body::Wrapper
 			# Wrap a response body with a metric.
 			#
@@ -56,7 +57,7 @@ def rewind
 			# @parameter error [Exception, nil] Optional error that caused the close.
 			def close(error = nil)
 				super
-				
+			ensure
 				@metric&.decrement
 				@metric = nil
 			end

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Ensure `requests_active` is decremented if closing the response body raises.
+
 ## v0.55.3
 
   - Decrement `requests_active` in `Falcon::Server#call` when `super` or `Falcon::Body::RequestFinished.wrap` raises, so utilization metrics are not leaked on error paths.

test/falcon/body/request_finished.rb

@@ -32,6 +32,25 @@
 				expect(metric.value).to be == 0
 			end
 
+			it "decrements metric when body close raises" do
+				body = Class.new(Protocol::HTTP::Body::Buffered) do
+					def close(error = nil)
+						super
+						raise RuntimeError, "close failed"
+					end
+				end.new(["Hello World"])
+				response = Protocol::HTTP::Response[200, {"content-type" => "text/plain"}, body]
+
+				metric.increment
+				subject.wrap(response, metric)
+
+				expect do
+					response.body.close
+				end.to raise_exception(RuntimeError, message: be =~ /close failed/)
+
+				expect(metric.value).to be == 0
+			end
+
 			it "decrements only once on multiple close calls" do
 				metric.increment
 				subject.wrap(response, metric)