Implement ServerConfig admin REST API (#3741)

Returns a valid config.json of the setup. In case of distributed
setup, it checks if quorum or more number of nodes have the same
config.json.

pkg/madmin/examples/get-config.go

@@ -0,0 +1,52 @@
+/* +build ignore
+ * Minio Cloud Storage, (C) 2017 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 main
+
+import (
+	"bytes"
+	"encoding/json"
+	"log"
+
+	"github.com/minio/minio/pkg/madmin"
+)
+
+func main() {
+	// Note: YOUR-ACCESSKEYID, YOUR-SECRETACCESSKEY are
+	// dummy values, please replace them with original values.
+
+	// API requests are secure (HTTPS) if secure=true and insecure (HTTPS) otherwise.
+	// New returns an Minio Admin client object.
+	madmClnt, err := madmin.New("your-minio.example.com:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	configBytes, err := madmClnt.GetConfig()
+	if err != nil {
+		log.Fatalf("failed due to: %v", err)
+	}
+
+	// Pretty-print config received as json.
+	var buf bytes.Buffer
+	err = json.Indent(&buf, configBytes, "", "\t")
+	if err != nil {
+		log.Fatalf("failed due to: %v", err)
+	}
+
+	log.Println("config received successfully: ", string(buf.Bytes()))
+}

pkg/madmin/examples/heal-bucket.go

@@ -29,9 +29,6 @@ func main() {
 	// Note: YOUR-ACCESSKEYID, YOUR-SECRETACCESSKEY are
 	// dummy values, please replace them with original values.
 
-	// Note: YOUR-ACCESSKEYID, YOUR-SECRETACCESSKEY are
-	// dummy values, please replace them with original values.
-
 	// API requests are secure (HTTPS) if secure=true and insecure (HTTPS) otherwise.
 	// New returns an Minio Admin client object.
 	madmClnt, err := madmin.New("your-minio.example.com:9000", "YOUR-ACCESSKEYID", "YOUR-SECRETACCESSKEY", true)