minio/cmd/admin-handlers.go

/*
 * Minio Cloud Storage, (C) 2016, 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 cmd

import (
	"bytes"
	"encoding/json"
	"encoding/xml"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"strconv"
	"sync"
	"time"

	"github.com/minio/minio/pkg/auth"
)

const (
	minioAdminOpHeader   = "X-Minio-Operation"
	minioConfigTmpFormat = "config-%s.json"

	maxConfigJSONSize = 256 * 1024 // 256KiB
)

// Type-safe query params.
type mgmtQueryKey string

// Only valid query params for mgmt admin APIs.
const (
	mgmtBucket       mgmtQueryKey = "bucket"
	mgmtObject       mgmtQueryKey = "object"
	mgmtPrefix       mgmtQueryKey = "prefix"
	mgmtLockDuration mgmtQueryKey = "duration"
	mgmtDelimiter    mgmtQueryKey = "delimiter"
	mgmtMarker       mgmtQueryKey = "marker"
	mgmtMaxKey       mgmtQueryKey = "max-key"
	mgmtDryRun       mgmtQueryKey = "dry-run"
)

// ServerVersion - server version
type ServerVersion struct {
	Version  string `json:"version"`
	CommitID string `json:"commitID"`
}

// ServerStatus - contains the response of service status API
type ServerStatus struct {
	ServerVersion ServerVersion `json:"serverVersion"`
	Uptime        time.Duration `json:"uptime"`
}

// ServiceStatusHandler - GET /?service
// HTTP header x-minio-operation: status
// ----------
// Fetches server status information like total disk space available
// to use, online disks, offline disks and quorum threshold.
func (adminAPI adminAPIHandlers) ServiceStatusHandler(w http.ResponseWriter, r *http.Request) {
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Fetch server version
	serverVersion := ServerVersion{Version: Version, CommitID: CommitID}

	// Fetch uptimes from all peers. This may fail to due to lack
	// of read-quorum availability.
	uptime, err := getPeerUptimes(globalAdminPeers)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		errorIf(err, "Possibly failed to get uptime from majority of servers.")
		return
	}

	// Create API response
	serverStatus := ServerStatus{
		ServerVersion: serverVersion,
		Uptime:        uptime,
	}

	// Marshal API response
	jsonBytes, err := json.Marshal(serverStatus)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to marshal storage info into json.")
		return
	}
	// Reply with storage information (across nodes in a
	// distributed setup) as json.
	writeSuccessResponseJSON(w, jsonBytes)
}

// ServiceRestartHandler - POST /?service
// HTTP header x-minio-operation: restart
// ----------
// Restarts minio server gracefully. In a distributed setup,  restarts
// all the servers in the cluster.
func (adminAPI adminAPIHandlers) ServiceRestartHandler(w http.ResponseWriter, r *http.Request) {
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Reply to the client before restarting minio server.
	writeSuccessResponseHeadersOnly(w)

	sendServiceCmd(globalAdminPeers, serviceRestart)
}

// setCredsReq request
type setCredsReq struct {
	Username string `xml:"username"`
	Password string `xml:"password"`
}

// ServiceCredsHandler - POST /?service
// HTTP header x-minio-operation: creds
// ----------
// Update credentials in a minio server. In a distributed setup, update all the servers
// in the cluster.
func (adminAPI adminAPIHandlers) ServiceCredentialsHandler(w http.ResponseWriter, r *http.Request) {
	// Authenticate request
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Avoid setting new credentials when they are already passed
	// by the environment.
	if globalIsEnvCreds {
		writeErrorResponse(w, ErrMethodNotAllowed, r.URL)
		return
	}

	// Load request body
	inputData, err := ioutil.ReadAll(r.Body)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		return
	}

	// Unmarshal request body
	var req setCredsReq
	err = xml.Unmarshal(inputData, &req)
	if err != nil {
		errorIf(err, "Cannot unmarshal credentials request")
		writeErrorResponse(w, ErrMalformedXML, r.URL)
		return
	}

	creds, err := auth.CreateCredentials(req.Username, req.Password)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Notify all other Minio peers to update credentials
	updateErrs := updateCredsOnPeers(creds)
	for peer, err := range updateErrs {
		errorIf(err, "Unable to update credentials on peer %s.", peer)
	}

	// Update local credentials in memory.
	prevCred := globalServerConfig.SetCredential(creds)

	// Save credentials to config file
	if err = globalServerConfig.Save(); err != nil {
		// Save the current creds when failed to update.
		globalServerConfig.SetCredential(prevCred)

		errorIf(err, "Unable to update the config with new credentials.")
		writeErrorResponse(w, ErrInternalError, r.URL)
		return
	}

	// At this stage, the operation is successful, return 200 OK
	w.WriteHeader(http.StatusOK)
}

// ServerProperties holds some server information such as, version, region
// uptime, etc..
type ServerProperties struct {
	Uptime   time.Duration `json:"uptime"`
	Version  string        `json:"version"`
	CommitID string        `json:"commitID"`
	Region   string        `json:"region"`
	SQSARN   []string      `json:"sqsARN"`
}

// ServerConnStats holds transferred bytes from/to the server
type ServerConnStats struct {
	TotalInputBytes  uint64 `json:"transferred"`
	TotalOutputBytes uint64 `json:"received"`
	Throughput       uint64 `json:"throughput,omitempty"`
}

// ServerHTTPMethodStats holds total number of HTTP operations from/to the server,
// including the average duration the call was spent.
type ServerHTTPMethodStats struct {
	Count       uint64 `json:"count"`
	AvgDuration string `json:"avgDuration"`
}

// ServerHTTPStats holds all type of http operations performed to/from the server
// including their average execution time.
type ServerHTTPStats struct {
	TotalHEADStats     ServerHTTPMethodStats `json:"totalHEADs"`
	SuccessHEADStats   ServerHTTPMethodStats `json:"successHEADs"`
	TotalGETStats      ServerHTTPMethodStats `json:"totalGETs"`
	SuccessGETStats    ServerHTTPMethodStats `json:"successGETs"`
	TotalPUTStats      ServerHTTPMethodStats `json:"totalPUTs"`
	SuccessPUTStats    ServerHTTPMethodStats `json:"successPUTs"`
	TotalPOSTStats     ServerHTTPMethodStats `json:"totalPOSTs"`
	SuccessPOSTStats   ServerHTTPMethodStats `json:"successPOSTs"`
	TotalDELETEStats   ServerHTTPMethodStats `json:"totalDELETEs"`
	SuccessDELETEStats ServerHTTPMethodStats `json:"successDELETEs"`
}

// ServerInfoData holds storage, connections and other
// information of a given server.
type ServerInfoData struct {
	StorageInfo StorageInfo      `json:"storage"`
	ConnStats   ServerConnStats  `json:"network"`
	HTTPStats   ServerHTTPStats  `json:"http"`
	Properties  ServerProperties `json:"server"`
}

// ServerInfo holds server information result of one node
type ServerInfo struct {
	Error string          `json:"error"`
	Addr  string          `json:"addr"`
	Data  *ServerInfoData `json:"data"`
}

// ServerInfoHandler - GET /?info
// ----------
// Get server information
func (adminAPI adminAPIHandlers) ServerInfoHandler(w http.ResponseWriter, r *http.Request) {
	// Authenticate request
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Web service response
	reply := make([]ServerInfo, len(globalAdminPeers))

	var wg sync.WaitGroup

	// Gather server information for all nodes
	for i, p := range globalAdminPeers {
		wg.Add(1)

		// Gather information from a peer in a goroutine
		go func(idx int, peer adminPeer) {
			defer wg.Done()

			// Initialize server info at index
			reply[idx] = ServerInfo{Addr: peer.addr}

			serverInfoData, err := peer.cmdRunner.ServerInfoData()
			if err != nil {
				errorIf(err, "Unable to get server info from %s.", peer.addr)
				reply[idx].Error = err.Error()
				return
			}

			reply[idx].Data = &serverInfoData
		}(i, p)
	}

	wg.Wait()

	// Marshal API response
	jsonBytes, err := json.Marshal(reply)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to marshal storage info into json.")
		return
	}

	// Reply with storage information (across nodes in a
	// distributed setup) as json.
	writeSuccessResponseJSON(w, jsonBytes)
}

// validateLockQueryParams - Validates query params for list/clear locks management APIs.
func validateLockQueryParams(vars url.Values) (string, string, time.Duration, APIErrorCode) {
	bucket := vars.Get(string(mgmtBucket))
	prefix := vars.Get(string(mgmtPrefix))
	durationStr := vars.Get(string(mgmtLockDuration))

	// N B empty bucket name is invalid
	if !IsValidBucketName(bucket) {
		return "", "", time.Duration(0), ErrInvalidBucketName
	}
	// empty prefix is valid.
	if !IsValidObjectPrefix(prefix) {
		return "", "", time.Duration(0), ErrInvalidObjectName
	}

	// If older-than parameter was empty then set it to 0s to list
	// all locks older than now.
	if durationStr == "" {
		durationStr = "0s"
	}
	duration, err := time.ParseDuration(durationStr)
	if err != nil {
		errorIf(err, "Failed to parse duration passed as query value.")
		return "", "", time.Duration(0), ErrInvalidDuration
	}

	return bucket, prefix, duration, ErrNone
}

// ListLocksHandler - GET /?lock&bucket=mybucket&prefix=myprefix&duration=duration
// - bucket is a mandatory query parameter
// - prefix and older-than are optional query parameters
// HTTP header x-minio-operation: list
// ---------
// Lists locks held on a given bucket, prefix and duration it was held for.
func (adminAPI adminAPIHandlers) ListLocksHandler(w http.ResponseWriter, r *http.Request) {
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	vars := r.URL.Query()
	bucket, prefix, duration, adminAPIErr := validateLockQueryParams(vars)
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Fetch lock information of locks matching bucket/prefix that
	// are available for longer than duration.
	volLocks, err := listPeerLocksInfo(globalAdminPeers, bucket, prefix, duration)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to fetch lock information from remote nodes.")
		return
	}

	// Marshal list of locks as json.
	jsonBytes, err := json.Marshal(volLocks)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to marshal lock information into json.")
		return
	}

	// Reply with list of locks held on bucket, matching prefix
	// held longer than duration supplied, as json.
	writeSuccessResponseJSON(w, jsonBytes)
}

// ClearLocksHandler - POST /?lock&bucket=mybucket&prefix=myprefix&duration=duration
// - bucket is a mandatory query parameter
// - prefix and older-than are optional query parameters
// HTTP header x-minio-operation: clear
// ---------
// Clear locks held on a given bucket, prefix and duration it was held for.
func (adminAPI adminAPIHandlers) ClearLocksHandler(w http.ResponseWriter, r *http.Request) {
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	vars := r.URL.Query()
	bucket, prefix, duration, adminAPIErr := validateLockQueryParams(vars)
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Fetch lock information of locks matching bucket/prefix that
	// are held for longer than duration.
	volLocks, err := listPeerLocksInfo(globalAdminPeers, bucket, prefix, duration)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to fetch lock information from remote nodes.")
		return
	}

	// Marshal list of locks as json.
	jsonBytes, err := json.Marshal(volLocks)
	if err != nil {
		writeErrorResponse(w, ErrInternalError, r.URL)
		errorIf(err, "Failed to marshal lock information into json.")
		return
	}

	// Remove lock matching bucket/prefix held longer than duration.
	for _, volLock := range volLocks {
		globalNSMutex.ForceUnlock(volLock.Bucket, volLock.Object)
	}

	// Reply with list of locks cleared, as json.
	writeSuccessResponseJSON(w, jsonBytes)
}

// extractListObjectsHealQuery - Validates query params for heal objects list management API.
func extractListObjectsHealQuery(vars url.Values) (string, string, string, string, int, APIErrorCode) {
	bucket := vars.Get(string(mgmtBucket))
	prefix := vars.Get(string(mgmtPrefix))
	marker := vars.Get(string(mgmtMarker))
	delimiter := vars.Get(string(mgmtDelimiter))
	maxKeyStr := vars.Get(string(mgmtMaxKey))

	// N B empty bucket name is invalid
	if !IsValidBucketName(bucket) {
		return "", "", "", "", 0, ErrInvalidBucketName
	}

	// empty prefix is valid.
	if !IsValidObjectPrefix(prefix) {
		return "", "", "", "", 0, ErrInvalidObjectName
	}

	// check if maxKey is a valid integer, if present.
	var maxKey int
	var err error
	if maxKeyStr != "" {
		if maxKey, err = strconv.Atoi(maxKeyStr); err != nil {
			return "", "", "", "", 0, ErrInvalidMaxKeys
		}
	}

	// Validate prefix, marker, delimiter and maxKey.
	apiErr := validateListObjectsArgs(prefix, marker, delimiter, maxKey)
	if apiErr != ErrNone {
		return "", "", "", "", 0, apiErr
	}

	return bucket, prefix, marker, delimiter, maxKey, ErrNone
}

// ListObjectsHealHandler - GET /?heal&bucket=mybucket&prefix=myprefix&marker=mymarker&delimiter=&mydelimiter&maxKey=1000
// - bucket is mandatory query parameter
// - rest are optional query parameters
// List upto maxKey objects that need healing in a given bucket matching the given prefix.
func (adminAPI adminAPIHandlers) ListObjectsHealHandler(w http.ResponseWriter, r *http.Request) {
	// Get object layer instance.
	objLayer := newObjectLayerFn()
	if objLayer == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Check if this setup has an erasure coded backend.
	if !globalIsXL {
		writeErrorResponse(w, ErrHealNotImplemented, r.URL)
		return
	}

	// Validate query params.
	vars := r.URL.Query()
	bucket, prefix, marker, delimiter, maxKey, adminAPIErr := extractListObjectsHealQuery(vars)
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Get the list objects to be healed.
	objectInfos, err := objLayer.ListObjectsHeal(bucket, prefix, marker, delimiter, maxKey)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	listResponse := generateListObjectsV1Response(bucket, prefix, marker, delimiter, maxKey, objectInfos)
	// Write success response.
	writeSuccessResponseXML(w, encodeResponse(listResponse))
}

// ListBucketsHealHandler - GET /?heal
func (adminAPI adminAPIHandlers) ListBucketsHealHandler(w http.ResponseWriter, r *http.Request) {
	// Get object layer instance.
	objLayer := newObjectLayerFn()
	if objLayer == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Check if this setup has an erasure coded backend.
	if !globalIsXL {
		writeErrorResponse(w, ErrHealNotImplemented, r.URL)
		return
	}

	// Get the list buckets to be healed.
	bucketsInfo, err := objLayer.ListBucketsHeal()
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	listResponse := generateListBucketsResponse(bucketsInfo)
	// Write success response.
	writeSuccessResponseXML(w, encodeResponse(listResponse))
}

// HealBucketHandler - POST /?heal&bucket=mybucket&dry-run
// - x-minio-operation = bucket
// - bucket is mandatory query parameter
// Heal a given bucket, if present.
func (adminAPI adminAPIHandlers) HealBucketHandler(w http.ResponseWriter, r *http.Request) {
	// Get object layer instance.
	objLayer := newObjectLayerFn()
	if objLayer == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Check if this setup has an erasure coded backend.
	if !globalIsXL {
		writeErrorResponse(w, ErrHealNotImplemented, r.URL)
		return
	}

	// Validate bucket name and check if it exists.
	vars := r.URL.Query()
	bucket := vars.Get(string(mgmtBucket))
	if err := checkBucketExist(bucket, objLayer); err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// if dry-run is present in query-params, then only perform validations and return success.
	if isDryRun(vars) {
		writeSuccessResponseHeadersOnly(w)
		return
	}

	// Heal the given bucket.
	err := objLayer.HealBucket(bucket)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Return 200 on success.
	writeSuccessResponseHeadersOnly(w)
}

// isDryRun - returns true if dry-run query param was set and false otherwise.
// otherwise.
func isDryRun(qval url.Values) bool {
	if _, dryRun := qval[string(mgmtDryRun)]; dryRun {
		return true
	}
	return false
}

// healResult - represents result of a heal operation like
// heal-object, heal-upload.
type healResult struct {
	State healState `json:"state"`
}

// healState - different states of heal operation
type healState int

const (
	// healNone - none of the disks healed
	healNone healState = iota
	// healPartial - some disks were healed, others were offline
	healPartial
	// healOK - all disks were healed
	healOK
)

// newHealResult - returns healResult given number of disks healed and
// number of disks offline
func newHealResult(numHealedDisks, numOfflineDisks int) healResult {
	var state healState
	switch {
	case numHealedDisks == 0:
		state = healNone

	case numOfflineDisks > 0:
		state = healPartial

	default:
		state = healOK
	}

	return healResult{State: state}
}

// HealObjectHandler - POST /?heal&bucket=mybucket&object=myobject&dry-run
// - x-minio-operation = object
// - bucket and object are both mandatory query parameters
// Heal a given object, if present.
func (adminAPI adminAPIHandlers) HealObjectHandler(w http.ResponseWriter, r *http.Request) {
	// Get object layer instance.
	objLayer := newObjectLayerFn()
	if objLayer == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Check if this setup has an erasure coded backend.
	if !globalIsXL {
		writeErrorResponse(w, ErrHealNotImplemented, r.URL)
		return
	}

	vars := r.URL.Query()
	bucket := vars.Get(string(mgmtBucket))
	object := vars.Get(string(mgmtObject))

	// Validate bucket and object names.
	if err := checkBucketAndObjectNames(bucket, object); err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Check if object exists.
	if _, err := objLayer.GetObjectInfo(bucket, object); err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// if dry-run is set in query params then perform validations
	// and return success.
	if isDryRun(vars) {
		writeSuccessResponseHeadersOnly(w)
		return
	}

	numOfflineDisks, numHealedDisks, err := objLayer.HealObject(bucket, object)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	jsonBytes, err := json.Marshal(newHealResult(numHealedDisks, numOfflineDisks))
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Return 200 on success.
	writeSuccessResponseJSON(w, jsonBytes)
}

// HealFormatHandler - POST /?heal&dry-run
// - x-minio-operation = format
// - bucket and object are both mandatory query parameters
// Heal a given object, if present.
func (adminAPI adminAPIHandlers) HealFormatHandler(w http.ResponseWriter, r *http.Request) {
	// Get current object layer instance.
	objectAPI := newObjectLayerFn()
	if objectAPI == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Check if this setup is an erasure code backend, since
	// heal-format is only applicable to single node XL and
	// distributed XL setup.
	if !globalIsXL {
		writeErrorResponse(w, ErrHealNotImplemented, r.URL)
		return
	}

	// if dry-run is set in query-params, return success as
	// validations are successful so far.
	vars := r.URL.Query()
	if isDryRun(vars) {
		writeSuccessResponseHeadersOnly(w)
		return
	}

	// Create a new set of storage instances to heal format.json.
	bootstrapDisks, err := initStorageDisks(globalEndpoints)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Wrap into retrying disks
	retryingDisks := initRetryableStorageDisks(bootstrapDisks,
		time.Millisecond, time.Millisecond*5, globalStorageHealthCheckInterval, globalStorageRetryThreshold)

	// Heal format.json on available storage.
	err = healFormatXL(retryingDisks)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Instantiate new object layer with newly formatted storage.
	newObjectAPI, err := newXLObjects(retryingDisks)
	if err != nil {
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// Set object layer with newly formatted storage to globalObjectAPI.
	globalObjLayerMutex.Lock()
	globalObjectAPI = newObjectAPI
	globalObjLayerMutex.Unlock()

	// Shutdown storage belonging to old object layer instance.
	objectAPI.Shutdown()

	// Inform peers to reinitialize storage with newly formatted storage.
	reInitPeerDisks(globalAdminPeers)

	// Return 200 on success.
	writeSuccessResponseHeadersOnly(w)
}

// GetConfigHandler - GET /?config
// - x-minio-operation = get
// Get config.json of this minio setup.
func (adminAPI adminAPIHandlers) GetConfigHandler(w http.ResponseWriter, r *http.Request) {
	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// check if objectLayer is initialized, if not return.
	if newObjectLayerFn() == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Get config.json from all nodes. In a single node setup, it
	// returns local config.json.
	configBytes, err := getPeerConfig(globalAdminPeers)
	if err != nil {
		errorIf(err, "Failed to get config from peers")
		writeErrorResponse(w, toAdminAPIErrCode(err), r.URL)
		return
	}

	writeSuccessResponseJSON(w, configBytes)
}

// toAdminAPIErrCode - converts errXLWriteQuorum error to admin API
// specific error.
func toAdminAPIErrCode(err error) APIErrorCode {
	switch err {
	case errXLWriteQuorum:
		return ErrAdminConfigNoQuorum
	}
	return toAPIErrorCode(err)
}

// SetConfigResult - represents detailed results of a set-config
// operation.
type nodeSummary struct {
	Name   string `json:"name"`
	ErrSet bool   `json:"errSet"`
	ErrMsg string `json:"errMsg"`
}

type setConfigResult struct {
	NodeResults []nodeSummary `json:"nodeResults"`
	Status      bool          `json:"status"`
}

// writeSetConfigResponse - writes setConfigResult value as json depending on the status.
func writeSetConfigResponse(w http.ResponseWriter, peers adminPeers, errs []error, status bool, reqURL *url.URL) {
	var nodeResults []nodeSummary
	// Build nodeResults based on error values received during
	// set-config operation.
	for i := range errs {
		nodeResults = append(nodeResults, nodeSummary{
			Name:   peers[i].addr,
			ErrSet: errs[i] != nil,
			ErrMsg: fmt.Sprintf("%v", errs[i]),
		})

	}

	result := setConfigResult{
		Status:      status,
		NodeResults: nodeResults,
	}

	// The following elaborate json encoding is to avoid escaping
	// '<', '>' in <nil>. Note: json.Encoder.Encode() adds a
	// gratuitous "\n".
	var resultBuf bytes.Buffer
	enc := json.NewEncoder(&resultBuf)
	enc.SetEscapeHTML(false)
	jsonErr := enc.Encode(result)
	if jsonErr != nil {
		writeErrorResponse(w, toAPIErrorCode(jsonErr), reqURL)
		return
	}

	writeSuccessResponseJSON(w, resultBuf.Bytes())
	return
}

// SetConfigHandler - PUT /?config
// - x-minio-operation = set
func (adminAPI adminAPIHandlers) SetConfigHandler(w http.ResponseWriter, r *http.Request) {
	// Get current object layer instance.
	objectAPI := newObjectLayerFn()
	if objectAPI == nil {
		writeErrorResponse(w, ErrServerNotInitialized, r.URL)
		return
	}

	// Validate request signature.
	adminAPIErr := checkRequestAuthType(r, "", "", "")
	if adminAPIErr != ErrNone {
		writeErrorResponse(w, adminAPIErr, r.URL)
		return
	}

	// Read configuration bytes from request body.
	configBuf := make([]byte, maxConfigJSONSize+1)
	n, err := io.ReadFull(r.Body, configBuf)
	if err == nil {
		// More than maxConfigSize bytes were available
		writeErrorResponse(w, ErrAdminConfigTooLarge, r.URL)
		return
	}
	if err != io.ErrUnexpectedEOF {
		errorIf(err, "Failed to read config from request body.")
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	configBytes := configBuf[:n]

	// Validate JSON provided in the request body: check the
	// client has not sent JSON objects with duplicate keys.
	if err = checkDupJSONKeys(string(configBytes)); err != nil {
		errorIf(err, "config contains duplicate JSON entries.")
		writeErrorResponse(w, ErrAdminConfigBadJSON, r.URL)
		return
	}

	var config serverConfig
	err = json.Unmarshal(configBytes, &config)
	if err != nil {
		errorIf(err, "Failed to unmarshal JSON configuration", err)
		writeErrorResponse(w, toAPIErrorCode(err), r.URL)
		return
	}

	// If credentials for the server are provided via environment,
	// then credentials in the provided configuration must match.
	if globalIsEnvCreds {
		creds := globalServerConfig.GetCredential()
		if config.Credential.AccessKey != creds.AccessKey ||
			config.Credential.SecretKey != creds.SecretKey {
			writeErrorResponse(w, ErrAdminCredentialsMismatch, r.URL)
			return
		}
	}

	// Write config received from request onto a temporary file on
	// all nodes.
	tmpFileName := fmt.Sprintf(minioConfigTmpFormat, mustGetUUID())
	errs := writeTmpConfigPeers(globalAdminPeers, tmpFileName, configBytes)

	// Check if the operation succeeded in quorum or more nodes.
	rErr := reduceWriteQuorumErrs(errs, nil, len(globalAdminPeers)/2+1)
	if rErr != nil {
		writeSetConfigResponse(w, globalAdminPeers, errs, false, r.URL)
		return
	}

	// Take a lock on minio/config.json. NB minio is a reserved
	// bucket name and wouldn't conflict with normal object
	// operations.
	configLock := globalNSMutex.NewNSLock(minioReservedBucket, minioConfigFile)
	if configLock.GetLock(globalObjectTimeout) != nil {
		writeErrorResponse(w, ErrOperationTimedOut, r.URL)
		return
	}
	defer configLock.Unlock()

	// Rename the temporary config file to config.json
	errs = commitConfigPeers(globalAdminPeers, tmpFileName)
	rErr = reduceWriteQuorumErrs(errs, nil, len(globalAdminPeers)/2+1)
	if rErr != nil {
		writeSetConfigResponse(w, globalAdminPeers, errs, false, r.URL)
		return
	}

	// serverMux (cmd/server-mux.go) implements graceful shutdown,
	// where all listeners are closed and process restart/shutdown
	// happens after 5s or completion of all ongoing http
	// requests, whichever is earlier.
	writeSetConfigResponse(w, globalAdminPeers, errs, true, r.URL)

	// Restart all node for the modified config to take effect.
	sendServiceCmd(globalAdminPeers, serviceRestart)
}