server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/logger-file-hook.go

@@ -0,0 +1,75 @@
+/*
+ * Minio Cloud Storage, (C) 2015, 2016 Minio, Inc.
+ *
+ * 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 cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/Sirupsen/logrus"
+)
+
+type fileLogger struct {
+	Enable   bool   `json:"enable"`
+	Filename string `json:"fileName"`
+	Level    string `json:"level"`
+}
+
+type localFile struct {
+	*os.File
+}
+
+func enableFileLogger() {
+	flogger := serverConfig.GetFileLogger()
+	if !flogger.Enable || flogger.Filename == "" {
+		return
+	}
+
+	// Creates the named file with mode 0666, honors system umask.
+	file, err := os.OpenFile(flogger.Filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0666)
+	fatalIf(err, "Unable to open log file.")
+
+	// Add a local file hook.
+	log.Hooks.Add(&localFile{file})
+
+	lvl, err := logrus.ParseLevel(flogger.Level)
+	fatalIf(err, "Unknown log level found in the config file.")
+
+	// Set default JSON formatter.
+	log.Formatter = new(logrus.JSONFormatter)
+	log.Level = lvl // Minimum log level.
+}
+
+// Fire fires the file logger hook and logs to the file.
+func (l *localFile) Fire(entry *logrus.Entry) error {
+	line, err := entry.String()
+	if err != nil {
+		return fmt.Errorf("Unable to read entry, %v", err)
+	}
+	l.File.Write([]byte(line + "\n"))
+	l.File.Sync()
+	return nil
+}
+
+// Levels - indicate log levels supported.
+func (l *localFile) Levels() []logrus.Level {
+	return []logrus.Level{
+		logrus.PanicLevel,
+		logrus.FatalLevel,
+		logrus.ErrorLevel,
+	}
+}