support iobuffer pool error write to log (#61)

buffer/iobuffer_pool.go

@@ -81,5 +81,9 @@ func NewIoBuffer(size int) IoBuffer {
 
 // PutIoBuffer is a a wrapper for ibPool
 func PutIoBuffer(buf IoBuffer) error {
-	return ibPool.PutIoBuffer(buf)
+	err := ibPool.PutIoBuffer(buf)
+	if err != nil {
+		logFunc(err.Error())
+	}
+	return err
 }

buffer/log.go

@@ -0,0 +1,35 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 buffer
+
+import (
+	"fmt"
+	"os"
+)
+
+// logFunc record buffer's error log, default to std error.
+// User can be overwrite it with any log implementation function
+// For example, use mosn.io/pkg/log logger.Errorf overwrite it.
+var logFunc = func(msg string) {
+	fmt.Fprintf(os.Stderr, "%s", msg)
+}
+
+// SetLogFunc use f overwrite logFunc.
+func SetLogFunc(f func(msg string)) {
+	logFunc = f
+}