minio/cmd/xl-v1-healing-common.go

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/*
* 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 (
"encoding/hex"
"path/filepath"
"time"
)
// commonTime returns a maximally occurring time from a list of time.
func commonTime(modTimes []time.Time) (modTime time.Time, count int) {
var maxima int // Counter for remembering max occurrence of elements.
timeOccurenceMap := make(map[time.Time]int)
// Ignore the uuid sentinel and count the rest.
for _, time := range modTimes {
if time == timeSentinel {
continue
}
timeOccurenceMap[time]++
}
// Find the common cardinality from previously collected
// occurrences of elements.
for time, count := range timeOccurenceMap {
if count == maxima && time.After(modTime) {
maxima = count
modTime = time
} else if count > maxima {
maxima = count
modTime = time
}
}
// Return the collected common uuid.
return modTime, maxima
}
// Beginning of unix time is treated as sentinel value here.
var timeSentinel = time.Unix(0, 0).UTC()
// Boot modTimes up to disk count, setting the value to time sentinel.
func bootModtimes(diskCount int) []time.Time {
modTimes := make([]time.Time, diskCount)
// Boots up all the modtimes.
for i := range modTimes {
modTimes[i] = timeSentinel
}
return modTimes
}
// Extracts list of times from xlMetaV1 slice and returns, skips
// slice elements which have errors.
func listObjectModtimes(partsMetadata []xlMetaV1, errs []error) (modTimes []time.Time) {
modTimes = bootModtimes(len(partsMetadata))
for index, metadata := range partsMetadata {
if errs[index] != nil {
continue
}
// Once the file is found, save the uuid saved on disk.
modTimes[index] = metadata.Stat.ModTime
}
return modTimes
}
// Notes:
// There are 5 possible states a disk could be in,
// 1. __online__ - has the latest copy of xl.json - returned by listOnlineDisks
//
// 2. __offline__ - err == errDiskNotFound
//
// 3. __availableWithParts__ - has the latest copy of xl.json and has all
// parts with checksums matching; returned by disksWithAllParts
//
// 4. __outdated__ - returned by outDatedDisk, provided []StorageAPI
// returned by diskWithAllParts is passed for latestDisks.
// - has an old copy of xl.json
// - doesn't have xl.json (errFileNotFound)
// - has the latest xl.json but one or more parts are corrupt
//
// 5. __missingParts__ - has the latest copy of xl.json but has some parts
// missing. This is identified separately since this may need manual
// inspection to understand the root cause. E.g, this could be due to
// backend filesystem corruption.
// listOnlineDisks - returns
// - a slice of disks where disk having 'older' xl.json (or nothing)
// are set to nil.
// - latest (in time) of the maximally occurring modTime(s).
func listOnlineDisks(disks []StorageAPI, partsMetadata []xlMetaV1, errs []error) (onlineDisks []StorageAPI, modTime time.Time) {
onlineDisks = make([]StorageAPI, len(disks))
// List all the file commit ids from parts metadata.
modTimes := listObjectModtimes(partsMetadata, errs)
// Reduce list of UUIDs to a single common value.
modTime, _ = commonTime(modTimes)
// Create a new online disks slice, which have common uuid.
for index, t := range modTimes {
if t == modTime {
onlineDisks[index] = disks[index]
} else {
onlineDisks[index] = nil
}
}
return onlineDisks, modTime
}
// outDatedDisks - return disks which don't have the latest object (i.e xl.json).
// disks that are offline are not 'marked' outdated.
func outDatedDisks(disks, latestDisks []StorageAPI, errs []error, partsMetadata []xlMetaV1,
bucket, object string) (outDatedDisks []StorageAPI) {
outDatedDisks = make([]StorageAPI, len(disks))
for index, latestDisk := range latestDisks {
if latestDisk != nil {
continue
}
// disk either has an older xl.json or doesn't have one.
switch errorCause(errs[index]) {
case nil, errFileNotFound:
outDatedDisks[index] = disks[index]
}
}
return outDatedDisks
}
// Returns if the object should be healed.
func xlShouldHeal(disks []StorageAPI, partsMetadata []xlMetaV1, errs []error, bucket, object string) bool {
onlineDisks, _ := listOnlineDisks(disks, partsMetadata,
errs)
// Return true even if one of the disks have stale data.
for _, disk := range onlineDisks {
if disk == nil {
return true
}
}
// Check if all parts of an object are available and their
// checksums are valid.
availableDisks, _, err := disksWithAllParts(onlineDisks, partsMetadata,
errs, bucket, object)
if err != nil {
// Note: This error is due to failure of blake2b
// checksum computation of a part. It doesn't clearly
// indicate if the object needs healing. At this
// juncture healing could fail with the same
// error. So, we choose to return that there is no
// need to heal.
return false
}
// Return true even if one disk has xl.json or one or more
// parts missing.
for _, disk := range availableDisks {
if disk == nil {
return true
}
}
return false
}
// xlHealStat - returns a structure which describes how many data,
// parity erasure blocks are missing and if it is possible to heal
// with the blocks present.
func xlHealStat(xl xlObjects, partsMetadata []xlMetaV1, errs []error) HealObjectInfo {
// Less than quorum erasure coded blocks of the object have the same create time.
// This object can't be healed with the information we have.
modTime, count := commonTime(listObjectModtimes(partsMetadata, errs))
if count < xl.readQuorum {
return HealObjectInfo{
Status: quorumUnavailable,
MissingDataCount: 0,
MissingParityCount: 0,
}
}
// If there isn't a valid xlMeta then we can't heal the object.
xlMeta, err := pickValidXLMeta(partsMetadata, modTime)
if err != nil {
return HealObjectInfo{
Status: corrupted,
MissingDataCount: 0,
MissingParityCount: 0,
}
}
// Compute heal statistics like bytes to be healed, missing
// data and missing parity count.
missingDataCount := 0
missingParityCount := 0
disksMissing := false
for i, err := range errs {
// xl.json is not found, which implies the erasure
// coded blocks are unavailable in the corresponding disk.
// First half of the disks are data and the rest are parity.
switch realErr := errorCause(err); realErr {
case errDiskNotFound:
disksMissing = true
fallthrough
case errFileNotFound:
if xlMeta.Erasure.Distribution[i]-1 < xl.dataBlocks {
missingDataCount++
} else {
missingParityCount++
}
}
}
// The object may not be healed completely, since some of the
// disks needing healing are unavailable.
if disksMissing {
return HealObjectInfo{
Status: canPartiallyHeal,
MissingDataCount: missingDataCount,
MissingParityCount: missingParityCount,
}
}
// This object can be healed. We have enough object metadata
// to reconstruct missing erasure coded blocks.
return HealObjectInfo{
Status: canHeal,
MissingDataCount: missingDataCount,
MissingParityCount: missingParityCount,
}
}
// disksWithAllParts - This function needs to be called with
// []StorageAPI returned by listOnlineDisks. Returns,
// - disks which have all parts specified in the latest xl.json.
// - errs updated to have errFileNotFound in place of disks that had
// missing parts.
// - non-nil error if any of the online disks failed during
// calculating blake2b checksum.
func disksWithAllParts(onlineDisks []StorageAPI, partsMetadata []xlMetaV1, errs []error, bucket, object string) ([]StorageAPI, []error, error) {
availableDisks := make([]StorageAPI, len(onlineDisks))
for index, onlineDisk := range onlineDisks {
if onlineDisk == nil {
continue
}
// disk has a valid xl.json but may not have all the
// parts. This is considered an outdated disk, since
// it needs healing too.
for _, part := range partsMetadata[index].Parts {
// compute blake2b sum of part.
partPath := filepath.Join(object, part.Name)
hash := newHash(partsMetadata[index].Erasure.Algorithm)
blakeBytes, hErr := hashSum(onlineDisk, bucket, partPath, hash)
if hErr == errFileNotFound {
errs[index] = errFileNotFound
availableDisks[index] = nil
break
}
if hErr != nil && hErr != errFileNotFound {
return nil, nil, traceError(hErr)
}
partChecksum := partsMetadata[index].Erasure.GetCheckSumInfo(part.Name).Hash
blakeSum := hex.EncodeToString(blakeBytes)
// if blake2b sum doesn't match for a part
// then this disk is outdated and needs
// healing.
if blakeSum != partChecksum {
errs[index] = errFileNotFound
availableDisks[index] = nil
break
}
availableDisks[index] = onlineDisk
}
}
return availableDisks, errs, nil
}