ktesting: tone down warning about leaked test goroutine

Not terminating immediately is fairly normal: many controllers
log "terminating" messages while they shut down, which often is
right after test completion, if that is when the test cancels the
context and then doesn't wait for goroutines (which is often
not possible).

Therefore the warning now only gets printed if that happens after more than 10
seconds since test completion, and then the warning is only printed as an info
message, not an error.

ktesting/testinglogger.go

@@ -217,8 +217,19 @@ type tloggerShared struct {
 	// t gets cleared when the test is completed.
 	t TL
 
-	// We warn once when a leaked goroutine is detected because
-	// it logs after test completion.
+	// The time when the test completed.
+	stopTime time.Time
+
+	// We warn once when a leaked goroutine logs after test completion.
+	//
+	// Not terminating immediately is fairly normal: many controllers
+	// log "terminating" messages while they shut down, which often is
+	// right after test completion, if that is when the test cancels the
+	// context and then doesn't wait for goroutines (which is often
+	// not possible).
+	//
+	// Therefore there is the [stopGracePeriod] during which messages get
+	// logged to the global logger without the warning.
 	goroutineWarningDone bool
 
 	formatter serialize.Formatter
@@ -228,10 +239,15 @@ type tloggerShared struct {
 	callDepth int
 }
 
+// Log output of a leaked goroutine during this period after test completion
+// does not trigger the warning.
+const stopGracePeriod = 10 * time.Second
+
 func (ls *tloggerShared) stop() {
 	ls.mutex.Lock()
 	defer ls.mutex.Unlock()
 	ls.t = nil
+	ls.stopTime = time.Now()
 }
 
 // tlogger is the actual LogSink implementation.
@@ -241,6 +257,8 @@ type tlogger struct {
 	values []interface{}
 }
 
+// fallbackLogger is called while l.shared.mutex is locked and after it has
+// been determined that the original testing.TB is no longer usable.
 func (l tlogger) fallbackLogger() logr.Logger {
 	logger := klog.Background().WithValues(l.values...).WithName(l.shared.testName + " leaked goroutine")
 	if l.prefix != "" {
@@ -250,8 +268,12 @@ func (l tlogger) fallbackLogger() logr.Logger {
 	logger = logger.WithCallDepth(l.shared.callDepth + 1)
 
 	if !l.shared.goroutineWarningDone {
-		logger.WithCallDepth(1).Error(nil, "WARNING: test kept at least one goroutine running after test completion", "callstack", string(dbg.Stacks(false)))
-		l.shared.goroutineWarningDone = true
+		duration := time.Since(l.shared.stopTime)
+		if duration > stopGracePeriod {
+
+			logger.WithCallDepth(1).Info("WARNING: test kept at least one goroutine running after test completion", "timeSinceCompletion", duration.Round(time.Second), "callstack", string(dbg.Stacks(false)))
+			l.shared.goroutineWarningDone = true
+		}
 	}
 	return logger
 }

ktesting/testinglogger_test.go

@@ -16,6 +16,7 @@ import (
 	"runtime"
 	"sync"
 	"testing"
+	"time"
 
 	"k8s.io/klog/v2"
 	"k8s.io/klog/v2/internal/test/require"
@@ -198,6 +199,7 @@ func TestStop(t *testing.T) {
 			_, _, line, _ = runtime.Caller(0)
 			logger.Info("simple info message")
 			logger.Error(nil, "error message")
+			time.Sleep(15 * time.Second)
 			logger.WithName("me").WithValues("completed", true).Info("complex info message", "anotherValue", 1)
 		}()
 	})
@@ -212,11 +214,14 @@ func TestStop(t *testing.T) {
 	// Strip time and pid prefix.
 	actual = regexp.MustCompile(`(?m)^.* testinglogger_test.go:`).ReplaceAllString(actual, `testinglogger_test.go:`)
 
+	// Strip duration.
+	actual = regexp.MustCompile(`timeSinceCompletion="\d+s"`).ReplaceAllString(actual, `timeSinceCompletion="<...>s"`)
+
 	// All lines from the callstack get stripped. We can be sure that it was non-empty because otherwise we wouldn't
 	// have the < > markers.
 	//
 	// Full output:
-	// 	testinglogger_test.go:194] "WARNING: test kept at least one goroutine running after test completion" logger="TestStop/Sub leaked goroutine" callstack=<
+	// 	testinglogger_test.go:194] "WARNING: test kept at least one goroutine running after test completion" logger="TestStop/Sub leaked goroutine.me" completed=true timeSinceCompletion="15s" callstack=<
 	//        	goroutine 23 [running]:
 	//        	k8s.io/klog/v2/internal/dbg.Stacks(0x0)
 	//        		/nvme/gopath/src/k8s.io/klog/internal/dbg/dbg.go:34 +0x8a
@@ -233,13 +238,13 @@ func TestStop(t *testing.T) {
 	//         >
 	actual = regexp.MustCompile(`(?m)^\t.*?\n`).ReplaceAllString(actual, ``)
 
-	expected := fmt.Sprintf(`testinglogger_test.go:%d] "WARNING: test kept at least one goroutine running after test completion" logger="TestStop/Sub leaked goroutine" callstack=<
- >
-testinglogger_test.go:%d] "simple info message" logger="TestStop/Sub leaked goroutine"
+	expected := fmt.Sprintf(`testinglogger_test.go:%d] "simple info message" logger="TestStop/Sub leaked goroutine"
 testinglogger_test.go:%d] "error message" logger="TestStop/Sub leaked goroutine"
+testinglogger_test.go:%d] "WARNING: test kept at least one goroutine running after test completion" logger="TestStop/Sub leaked goroutine.me" completed=true timeSinceCompletion="<...>s" callstack=<
+ >
 testinglogger_test.go:%d] "complex info message" logger="TestStop/Sub leaked goroutine.me" completed=true anotherValue=1
 `,
-		line+1, line+1, line+2, line+3)
+		line+1, line+2, line+4, line+4)
 	if actual != expected {
 		t.Errorf("Output does not match. Expected:\n%s\nActual:\n%s\n", expected, actual)
 	}