use NilFormatter to discard log, because assigning entry.Logger.Out = ioutil.Discard will cause all subsequent log missing

auxten · auxten · commit 48c5c4786274 · 2018-08-03T21:36:43.000+08:00
diff --git a/utils/log/logwrapper.go b/utils/log/logwrapper.go
@@ -19,7 +19,6 @@ package log
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -68,7 +67,9 @@ func (hook *CallerHook) Fire(entry *logrus.Entry) error {
 	if len(fields) > 0 {
 		level, ok := PkgDebugLogFilter[fields[0]]
 		if ok && entry.Level > level {
-			entry.Logger.Out = ioutil.Discard
+			nilLogger := logrus.New()
+			nilLogger.Formatter = &NilFormatter{}
+			entry.Logger = nilLogger
 			return nil
 		}
 	}
diff --git a/utils/log/nillogger.go b/utils/log/nillogger.go
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2018 The ThunderDB Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package log
+
+import (
+	"github.com/sirupsen/logrus"
+)
+
+// NilFormatter just discards the log entry
+type NilFormatter struct{}
+
+// Format just return nil, nil for discarding log entry
+func (f *NilFormatter) Format(entry *logrus.Entry) ([]byte, error) {
+	return nil, nil
+}
