server: save and compare multiple disks are used (#1474)

When server is run with multiple disks which uses xl interface where
order and count of disks are important, this patch saves such disks
configuration and compares in next run if there is a mismatch.

Fixes #1458

config.go

@@ -86,3 +86,26 @@ func getConfigFile() (string, error) {
 	}
 	return filepath.Join(configPath, globalMinioConfigFile), nil
 }
+
+// isFormatConfigFileExists - returns true if format config file exists.
+func isFormatConfigFileExists() bool {
+	st, err := os.Stat(mustGetFormatConfigFile())
+	return (err == nil && st.Mode().IsRegular())
+}
+
+// mustGetFormatConfigFile must get format config file.
+func mustGetFormatConfigFile() string {
+	configFile, err := getFormatConfigFile()
+	fatalIf(err, "Unable to get format config file.", nil)
+
+	return configFile
+}
+
+// getFormatConfigFile get format config file.
+func getFormatConfigFile() (string, error) {
+	configPath, err := getConfigPath()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(configPath, globalMinioFormatConfigFile), nil
+}

format-config-v1.go

@@ -0,0 +1,111 @@
+/*
+ * Minio Cloud Storage, (C) 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 main
+
+import "github.com/minio/minio/pkg/quick"
+
+type fsFormat struct {
+	Version string `json:"version"`
+}
+
+type xlFormat struct {
+	Version string   `json:"version"`
+	Disks   []string `json:"disks"`
+}
+
+type formatConfigV1 struct {
+	// must have "Version" to "quick" to work
+	Version string   `json:"version"`
+	Format  string   `json:"format"`
+	FS      fsFormat `json:"fs,omitempty"`
+	XL      xlFormat `json:"xl,omitempty"`
+}
+
+func (f formatConfigV1) Save() error {
+	configFile, err := getFormatConfigFile()
+	if err != nil {
+		return err
+	}
+
+	// initialize quick.
+	qc, err := quick.New(&f)
+	if err != nil {
+		return err
+	}
+
+	// Save config file.
+	return qc.Save(configFile)
+}
+
+func (f *formatConfigV1) Load() error {
+	configFile, err := getFormatConfigFile()
+	if err != nil {
+		return err
+	}
+
+	f.Version = globalMinioConfigVersion
+	qc, err := quick.New(f)
+	if err != nil {
+		return err
+	}
+	if err := qc.Load(configFile); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// saveFormatFS - save FS format configuration
+func saveFormatFS(fs fsFormat) error {
+	config := formatConfigV1{Version: globalMinioConfigVersion, Format: "fs", FS: fs}
+	return config.Save()
+}
+
+// saveFormatXL - save XL format configuration
+func saveFormatXL(xl xlFormat) error {
+	config := formatConfigV1{Version: globalMinioConfigVersion, Format: "xl", XL: xl}
+	return config.Save()
+}
+
+// getSavedFormatConfig - get saved format configuration
+func getSavedFormatConfig() (formatConfigV1, error) {
+	config := formatConfigV1{Version: globalMinioConfigVersion}
+
+	if err := config.Load(); err != nil {
+		return config, err
+	}
+
+	return config, nil
+}
+
+// getFormatFS - get saved FS format configuration
+func getFormatFS() (fsFormat, error) {
+	config, err := getSavedFormatConfig()
+	if err != nil {
+		return fsFormat{}, err
+	}
+	return config.FS, nil
+}
+
+// getFormatXL - get saved XL format configuration
+func getFormatXL() (xlFormat, error) {
+	config, err := getSavedFormatConfig()
+	if err != nil {
+		return xlFormat{}, err
+	}
+	return config.XL, nil
+}

globals.go

@@ -29,12 +29,13 @@ const (
 
 // minio configuration related constants.
 const (
-	globalMinioConfigVersion = "4"
-	globalMinioConfigDir     = ".minio"
-	globalMinioCertsDir      = ".minio/certs"
-	globalMinioCertFile      = "public.crt"
-	globalMinioKeyFile       = "private.key"
-	globalMinioConfigFile    = "config.json"
+	globalMinioConfigVersion    = "4"
+	globalMinioConfigDir        = ".minio"
+	globalMinioCertsDir         = ".minio/certs"
+	globalMinioCertFile         = "public.crt"
+	globalMinioKeyFile          = "private.key"
+	globalMinioConfigFile       = "config.json"
+	globalMinioFormatConfigFile = "format.json"
 )
 
 var (

routers.go

@@ -17,7 +17,9 @@
 package main
 
 import (
+	"fmt"
 	"net/http"
+	"reflect"
 
 	router "github.com/gorilla/mux"
 )
@@ -36,6 +38,26 @@ func newObjectLayer(exportPaths ...string) (ObjectLayer, error) {
 
 // configureServer handler returns final handler for the http server.
 func configureServerHandler(srvCmdConfig serverCmdConfig) http.Handler {
+	// FIXME: currently we don't check single exportPath which uses FS layer.
+	if len(srvCmdConfig.exportPaths) > 1 {
+		if isFormatConfigFileExists() {
+			format, err := getFormatXL()
+			if err != nil {
+				fatalIf(err, "Failed to read format.json", nil)
+			}
+
+			if !reflect.DeepEqual(format.Disks, srvCmdConfig.exportPaths) {
+				err = fmt.Errorf("Number of export paths from command-line did not match the backend configuration. Backend is configured with [%s] exports.", format.Disks)
+				fatalIf(err, "", nil)
+			}
+		} else {
+			// First run: save disk configuration
+			if err := saveFormatXL(xlFormat{Version: "1", Disks: srvCmdConfig.exportPaths}); err != nil {
+				fatalIf(err, "Unable to save 'format.json'", nil)
+			}
+		}
+	}
+
 	objAPI, err := newObjectLayer(srvCmdConfig.exportPaths...)
 	fatalIf(err, "Initializing object layer failed.", nil)