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.go

@@ -0,0 +1,88 @@
+/*
+ * 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 (
+	"bufio"
+	"bytes"
+	"runtime/debug"
+	"strings"
+
+	"github.com/Sirupsen/logrus"
+)
+
+type fields map[string]interface{}
+
+var log = logrus.New() // Default console logger.
+
+// logger carries logging configuration for various supported loggers.
+// Currently supported loggers are
+//
+//   - console [default]
+//   - file
+//   - syslog
+type logger struct {
+	Console consoleLogger `json:"console"`
+	File    fileLogger    `json:"file"`
+	Syslog  syslogLogger  `json:"syslog"`
+	// Add new loggers here.
+}
+
+// stackInfo returns printable stack trace.
+func stackInfo() string {
+	// Convert stack-trace bytes to io.Reader.
+	rawStack := bufio.NewReader(bytes.NewBuffer(debug.Stack()))
+	// Skip stack trace lines until our real caller.
+	for i := 0; i <= 4; i++ {
+		rawStack.ReadLine()
+	}
+
+	// Read the rest of useful stack trace.
+	stackBuf := new(bytes.Buffer)
+	stackBuf.ReadFrom(rawStack)
+
+	// Strip GOPATH of the build system and return.
+	return strings.Replace(stackBuf.String(), GOPATH+"/src/", "", -1)
+}
+
+// errorIf synonymous with fatalIf but doesn't exit on error != nil
+func errorIf(err error, msg string, data ...interface{}) {
+	if err == nil {
+		return
+	}
+	fields := logrus.Fields{
+		"cause": err.Error(),
+	}
+	if globalTrace {
+		fields["stack"] = "\n" + stackInfo()
+	}
+	log.WithFields(fields).Errorf(msg, data...)
+}
+
+// fatalIf wrapper function which takes error and prints jsonic error messages.
+func fatalIf(err error, msg string, data ...interface{}) {
+	if err == nil {
+		return
+	}
+	fields := logrus.Fields{
+		"cause": err.Error(),
+	}
+	if globalTrace {
+		fields["stack"] = "\n" + stackInfo()
+	}
+	log.WithFields(fields).Fatalf(msg, data...)
+}