test panic log text

staging/src/k8s.io/apimachinery/pkg/util/runtime/runtime_test.go

@@ -17,7 +17,12 @@ limitations under the License.
 package runtime
 
 import (
+	"bytes"
 	"fmt"
+	"io"
+	"os"
+	"regexp"
+	"strings"
 	"testing"
 )
 
@@ -69,3 +74,66 @@ func TestCustomHandleError(t *testing.T) {
 		t.Errorf("did not receive custom handler")
 	}
 }
+
+func TestHandleCrashLog(t *testing.T) {
+	log, err := captureStderr(func() {
+		defer func() {
+			if r := recover(); r == nil {
+				t.Fatalf("expected a panic to recover from")
+			}
+		}()
+		defer HandleCrash()
+		panic("test panic")
+	})
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	// Example log:
+	//
+	// ...] Observed a panic: test panic
+	// goroutine 6 [running]:
+	// command-line-arguments.logPanic(0x..., 0x...)
+	// 	.../src/k8s.io/kubernetes/staging/src/k8s.io/apimachinery/pkg/util/runtime/runtime.go:69 +0x...
+	lines := strings.Split(log, "\n")
+	if len(lines) < 4 {
+		t.Fatalf("panic log should have 1 line of message, 1 line per goroutine and 2 lines per function call")
+	}
+	if match, _ := regexp.MatchString("Observed a panic: test panic", lines[0]); !match {
+		t.Errorf("mismatch panic message: %s", lines[0])
+	}
+	// The following regexp's verify that Kubernetes panic log matches Golang stdlib
+	// stacktrace pattern. We need to update these regexp's if stdlib changes its pattern.
+	if match, _ := regexp.MatchString(`goroutine [0-9]+ \[.+\]:`, lines[1]); !match {
+		t.Errorf("mismatch goroutine: %s", lines[1])
+	}
+	if match, _ := regexp.MatchString(`logPanic(.*)`, lines[2]); !match {
+		t.Errorf("mismatch symbolized function name: %s", lines[2])
+	}
+	if match, _ := regexp.MatchString(`runtime\.go:[0-9]+ \+0x`, lines[3]); !match {
+		t.Errorf("mismatch file/line/offset information: %s", lines[3])
+	}
+}
+
+// captureStderr redirects stderr to result string, and then restore stderr from backup
+func captureStderr(f func()) (string, error) {
+	r, w, err := os.Pipe()
+	if err != nil {
+		return "", err
+	}
+	bak := os.Stderr
+	os.Stderr = w
+	defer func() { os.Stderr = bak }()
+
+	resultCh := make(chan string)
+	// copy the output in a separate goroutine so printing can't block indefinitely
+	go func() {
+		var buf bytes.Buffer
+		io.Copy(&buf, r)
+		resultCh <- buf.String()
+	}()
+
+	f()
+	w.Close()
+
+	return <-resultCh, nil
+}