Extract limited stack trace frames from error

maintenance/terminationlog/termlog.go

@@ -9,16 +9,23 @@ package terminationlog
 
 import (
 	"fmt"
+	"github.com/pkg/errors"
 	"github.com/rs/zerolog/log"
 	"os"
 )
 
 var logFile *os.File
 
+const LogFileLimit = 4096 // bytes;
+
+type stackTracer interface {
+	StackTrace() errors.StackTrace
+}
+
 // Fatalf implements log Fatalf interface
 func Fatalf(format string, v ...interface{}) {
 	if logFile != nil {
-		fmt.Fprintf(logFile, format, v...)
+		fmt.Fprint(logFile, limitLogFileOutput(fmt.Sprintf(format, v...)))
 	}
 
 	log.Fatal().Msg(fmt.Sprintf(format, v...))
@@ -27,7 +34,7 @@ func Fatalf(format string, v ...interface{}) {
 // Fatal implements log Fatal interface
 func Fatal(v ...interface{}) {
 	if logFile != nil {
-		fmt.Fprint(logFile, v...)
+		fmt.Fprint(logFile, limitLogFileOutput(fmt.Sprint(v...)))
 	}
 
 	log.Fatal().Msg(fmt.Sprint(v...))
@@ -37,3 +44,13 @@ func Fatal(v ...interface{}) {
 func Fatalln(v ...interface{}) {
 	Fatal(v...)
 }
+
+func limitLogFileOutput(s string) string {
+	sb := []byte(s)
+	limit := len(sb)
+	if limit > LogFileLimit {
+		limit = LogFileLimit
+	}
+
+	return string(sb[:limit])
+}

maintenance/terminationlog/termlog_test.go

@@ -0,0 +1,15 @@
+package terminationlog
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestTrimLogFileOutput(t *testing.T) {
+	b := make([]byte, 5000)
+	assert.Len(t, limitLogFileOutput(string(b)), 4096)
+	b = make([]byte, 2000)
+	assert.Len(t, limitLogFileOutput(string(b)), 2000)
+	b = make([]byte, 4096)
+	assert.Len(t, limitLogFileOutput(string(b)), 4096)
+}