Bug 1891143: pkg/cvo/metrics: Abandon child goroutines after shutdownContext expires

pkg/cvo/metrics.go

@@ -100,6 +100,11 @@ version for 'cluster', or empty for 'initial'.
 	}
 }
 
+type asyncResult struct {
+	name  string
+	error error
+}
+
 // RunMetrics launches an server bound to listenAddress serving
 // Prometheus metrics at /metrics over HTTP, and, if tlsConfig is
 // non-nil, also over HTTPS.  Continues serving until runContext.Done()
@@ -123,50 +128,60 @@ func RunMetrics(runContext context.Context, shutdownContext context.Context, lis
 	// HTTP, needed during upgrade, while still allowing TLS certs and end to end metrics protection.
 	mux := cmux.New(tcpListener)
 
-	errorChannel := make(chan error, 1)
-	errorChannelCount := 1
+	resultChannel := make(chan asyncResult, 1)
+	resultChannelCount := 1
 
 	go func() {
 		// match HTTP first
 		httpListener := mux.Match(cmux.HTTP1())
 		klog.Infof("Metrics port listening for HTTP on %v", listenAddress)
-		errorChannel <- server.Serve(httpListener)
+		err := server.Serve(httpListener)
+		resultChannel <- asyncResult{name: "HTTP server", error: err}
 	}()
 
 	if tlsConfig != nil {
-		errorChannelCount++
+		resultChannelCount++
 		go func() {
 			tlsListener := tls.NewListener(mux.Match(cmux.Any()), tlsConfig)
 			klog.Infof("Metrics port listening for HTTPS on %v", listenAddress)
-			errorChannel <- server.Serve(tlsListener)
+			err := server.Serve(tlsListener)
+			resultChannel <- asyncResult{name: "HTTPS server", error: err}
 		}()
 	}
 
-	errorChannelCount++
+	resultChannelCount++
 	go func() {
-		errorChannel <- mux.Serve()
+		err := mux.Serve()
+		resultChannel <- asyncResult{name: "TCP muxer", error: err}
 	}()
 
 	shutdown := false
 	var loopError error
-	for errorChannelCount > 0 {
+	for resultChannelCount > 0 {
 		if shutdown {
-			err := <-errorChannel
-			errorChannelCount--
-			if err != nil && err != http.ErrServerClosed && err != cmux.ErrListenerClosed {
-				if loopError == nil {
-					loopError = err
-				} else if err != nil { // log the error we are discarding
-					klog.Errorf("Failed to gracefully shut down metrics server: %s", err)
+			select {
+			case result := <-resultChannel:
+				resultChannelCount--
+				if result.error == nil {
+					klog.Infof("Collected metrics %s goroutine.", result.name)
+				} else {
+					klog.Errorf("Collected metrics %s goroutine: %v", result.name, result.error)
+					loopError = result.error
 				}
+			case <-shutdownContext.Done(): // out of time
+				klog.Errorf("Abandoning %d uncollected metrics goroutines", resultChannelCount)
+				return shutdownContext.Err()
 			}
 		} else {
 			select {
 			case <-runContext.Done(): // clean shutdown
-			case err := <-errorChannel: // crashed before a shutdown was requested
-				errorChannelCount--
-				if err != nil && err != http.ErrServerClosed && err != cmux.ErrListenerClosed {
-					loopError = err
+			case result := <-resultChannel: // crashed before a shutdown was requested
+				resultChannelCount--
+				if result.error == nil {
+					klog.Infof("Collected metrics %s goroutine.", result.name)
+				} else {
+					klog.Errorf("Collected metrics %s goroutine: %v", result.name, result.error)
+					loopError = result.error
 				}
 			}
 			shutdown = true