Migrate config.json from config-dir to backend (#6195)

This PR is the first set of changes to move the config
to the backend, the changes use the existing `config.json`
allows it to be migrated such that we can save it in on
backend disks.

In future releases, we will slowly migrate out of the
current architecture.

Fixes #6182

cmd/config.go

@@ -0,0 +1,261 @@
+/*
+ * Minio Cloud Storage, (C) 2018 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 (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"io/ioutil"
+	"path"
+	"runtime"
+	"time"
+
+	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/hash"
+	"github.com/minio/minio/pkg/quick"
+)
+
+const (
+	minioConfigPrefix = "config"
+
+	// Minio configuration file.
+	minioConfigFile = "config.json"
+)
+
+func saveServerConfig(objAPI ObjectLayer, config *serverConfig) error {
+	if err := quick.CheckData(config); err != nil {
+		return err
+	}
+
+	data, err := json.Marshal(config)
+	if err != nil {
+		return err
+	}
+
+	configFile := path.Join(minioConfigPrefix, minioConfigFile)
+	if globalEtcdClient != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+		_, err := globalEtcdClient.Put(ctx, configFile, string(data))
+		defer cancel()
+		return err
+	}
+
+	return saveConfig(objAPI, configFile, data)
+}
+
+func readConfigEtcd(configFile string) ([]byte, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	resp, err := globalEtcdClient.Get(ctx, configFile)
+	defer cancel()
+	if err != nil {
+		return nil, err
+	}
+	if resp.Count == 0 {
+		return nil, errConfigNotFound
+	}
+	for _, ev := range resp.Kvs {
+		if string(ev.Key) == configFile {
+			return ev.Value, nil
+		}
+	}
+	return nil, errConfigNotFound
+}
+
+func readServerConfig(ctx context.Context, objAPI ObjectLayer) (*serverConfig, error) {
+	var configData []byte
+	var err error
+	configFile := path.Join(minioConfigPrefix, minioConfigFile)
+	if globalEtcdClient != nil {
+		configData, err = readConfigEtcd(configFile)
+	} else {
+		var reader io.Reader
+		reader, err = readConfig(ctx, objAPI, configFile)
+		if err != nil {
+			return nil, err
+		}
+		configData, err = ioutil.ReadAll(reader)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	if runtime.GOOS == "windows" {
+		configData = bytes.Replace(configData, []byte("\r\n"), []byte("\n"), -1)
+	}
+
+	if err = quick.CheckDuplicateKeys(string(configData)); err != nil {
+		return nil, err
+	}
+
+	var config = &serverConfig{}
+	if err := json.Unmarshal(configData, config); err != nil {
+		return nil, err
+	}
+
+	if err := quick.CheckData(config); err != nil {
+		return nil, err
+	}
+
+	return config, nil
+}
+
+func checkServerConfigEtcd(configFile string) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	resp, err := globalEtcdClient.Get(ctx, configFile)
+	defer cancel()
+	if err != nil {
+		return err
+	}
+	if resp.Count == 0 {
+		return errConfigNotFound
+	}
+	return nil
+}
+
+func checkServerConfig(ctx context.Context, objAPI ObjectLayer) error {
+	configFile := path.Join(minioConfigPrefix, minioConfigFile)
+	if globalEtcdClient != nil {
+		return checkServerConfigEtcd(configFile)
+	}
+
+	if _, err := objAPI.GetObjectInfo(ctx, minioMetaBucket, configFile); err != nil {
+		if isErrObjectNotFound(err) {
+			return errConfigNotFound
+		}
+		logger.GetReqInfo(ctx).AppendTags("configFile", configFile)
+		logger.LogIf(ctx, err)
+		return err
+	}
+	return nil
+}
+
+func saveConfig(objAPI ObjectLayer, configFile string, data []byte) error {
+	hashReader, err := hash.NewReader(bytes.NewReader(data), int64(len(data)), "", getSHA256Hash(data))
+	if err != nil {
+		return err
+	}
+
+	_, err = objAPI.PutObject(context.Background(), minioMetaBucket, configFile, hashReader, nil)
+	return err
+}
+
+var errConfigNotFound = errors.New("config file not found")
+
+func readConfig(ctx context.Context, objAPI ObjectLayer, configFile string) (*bytes.Buffer, error) {
+	var buffer bytes.Buffer
+	// Read entire content by setting size to -1
+	if err := objAPI.GetObject(ctx, minioMetaBucket, configFile, 0, -1, &buffer, ""); err != nil {
+		// Ignore if err is ObjectNotFound or IncompleteBody when bucket is not configured with notification
+		if isErrObjectNotFound(err) || isErrIncompleteBody(err) || isInsufficientReadQuorum(err) {
+			return nil, errConfigNotFound
+		}
+
+		logger.GetReqInfo(ctx).AppendTags("configFile", configFile)
+		logger.LogIf(ctx, err)
+		return nil, err
+	}
+
+	// Return config not found on empty content.
+	if buffer.Len() == 0 {
+		return nil, errConfigNotFound
+	}
+
+	return &buffer, nil
+}
+
+// ConfigSys - config system.
+type ConfigSys struct{}
+
+// Load - load config.json.
+func (sys *ConfigSys) Load(objAPI ObjectLayer) error {
+	return sys.Init(objAPI)
+}
+
+// Init - initializes config system from config.json.
+func (sys *ConfigSys) Init(objAPI ObjectLayer) error {
+	if objAPI == nil {
+		return errInvalidArgument
+	}
+	return loadConfig(objAPI)
+}
+
+// NewConfigSys - creates new config system object.
+func NewConfigSys() *ConfigSys {
+	return &ConfigSys{}
+}
+
+// Migrates ${HOME}/.minio/config.json to '<export_path>/.minio.sys/config/minio.json'
+func migrateConfigToMinioSys() error {
+	// Construct path to config.json for the given bucket.
+	configFile := path.Join(bucketConfigPrefix, minioConfigFile)
+	transactionConfigFile := configFile + ".transaction"
+
+	// As object layer's GetObject() and PutObject() take respective lock on minioMetaBucket
+	// and configFile, take a transaction lock to avoid race.
+	objLock := globalNSMutex.NewNSLock(minioMetaBucket, transactionConfigFile)
+	if err := objLock.GetLock(globalOperationTimeout); err != nil {
+		return err
+	}
+	defer objLock.Unlock()
+
+	// Verify if backend already has the file.
+	if err := checkServerConfig(context.Background(), newObjectLayerFn()); err != errConfigNotFound {
+		return err
+	} // if errConfigNotFound proceed to migrate..
+
+	var config = &serverConfig{}
+	if _, err := Load(getConfigFile(), config); err != nil {
+		return err
+	}
+
+	return saveServerConfig(newObjectLayerFn(), config)
+}
+
+// Initialize and load config from remote etcd or local config directory
+func initConfig() {
+	if globalEtcdClient != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+		resp, err := globalEtcdClient.Get(ctx, getConfigFile())
+		cancel()
+		if err == nil && resp.Count > 0 {
+			logger.FatalIf(migrateConfig(), "Config migration failed")
+		}
+	} else {
+		if isFile(getConfigFile()) {
+			logger.FatalIf(migrateConfig(), "Config migration failed")
+
+			// Migrates ${HOME}/.minio/config.json to '<export_path>/.minio.sys/config/config.json'
+			if err := migrateConfigToMinioSys(); err != nil {
+				logger.Fatal(err, "Unable to migrate 'config.json' to '.minio.sys/config/config.json'")
+			}
+		}
+
+	}
+	if err := checkServerConfig(context.Background(), newObjectLayerFn()); err != nil {
+		if err == errConfigNotFound {
+			// Config file does not exist, we create it fresh and return upon success.
+			logger.FatalIf(newConfig(newObjectLayerFn()), "Unable to initialize minio config for the first time")
+			logger.Info("Created minio configuration file successfully at " + getConfigDir())
+		} else {
+			logger.FatalIf(err, "Unable to load the configuration file")
+		}
+	}
+	logger.FatalIf(loadConfig(newObjectLayerFn()), "Unable to load the configuration file")
+}