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xl-v1-healing-common.go
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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 (
"context"
"path/filepath"
"strings"
"time"
"github.com/pydio/minio-srv/cmd/logger"
)
// 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 || (count == maxima && time.After(modTime)) {
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
}
// Returns the latest updated xlMeta files and error in case of failure.
func getLatestXLMeta(ctx context.Context, partsMetadata []xlMetaV1, errs []error) (xlMetaV1, error) {
// There should be atleast half correct entries, if not return failure
if reducedErr := reduceReadQuorumErrs(ctx, errs, objectOpIgnoredErrs, globalXLSetDriveCount/2); reducedErr != nil {
return xlMetaV1{}, reducedErr
}
// List all the file commit ids from parts metadata.
modTimes := listObjectModtimes(partsMetadata, errs)
// Count all latest updated xlMeta values
var count int
var latestXLMeta xlMetaV1
// Reduce list of UUIDs to a single common value - i.e. the last updated Time
modTime, _ := commonTime(modTimes)
// Interate through all the modTimes and count the xlMeta(s) with latest time.
for index, t := range modTimes {
if t == modTime && partsMetadata[index].IsValid() {
latestXLMeta = partsMetadata[index]
count++
}
}
if count < len(partsMetadata)/2 {
return xlMetaV1{}, errXLReadQuorum
}
return latestXLMeta, nil
}
// disksWithAllParts - This function needs to be called with
// []StorageAPI returned by listOnlineDisks. Returns,
//
// - disks which have all parts specified in the latest xl.json.
//
// - slice of errors about the state of data files on disk - can have
// a not-found error or a hash-mismatch error.
func disksWithAllParts(ctx context.Context, onlineDisks []StorageAPI, partsMetadata []xlMetaV1, errs []error, bucket,
object string) ([]StorageAPI, []error) {
availableDisks := make([]StorageAPI, len(onlineDisks))
buffer := []byte{}
dataErrs := make([]error, len(onlineDisks))
for i, onlineDisk := range onlineDisks {
if onlineDisk == nil {
dataErrs[i] = errDiskNotFound
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[i].Parts {
partPath := filepath.Join(object, part.Name)
checksumInfo := partsMetadata[i].Erasure.GetChecksumInfo(part.Name)
verifier := NewBitrotVerifier(checksumInfo.Algorithm, checksumInfo.Hash)
// verification happens even if a 0-length
// buffer is passed
_, hErr := onlineDisk.ReadFile(bucket, partPath, 0, buffer, verifier)
isCorrupt := false
if hErr != nil {
isCorrupt = strings.HasPrefix(hErr.Error(), "Bitrot verification mismatch - expected ")
}
switch {
case isCorrupt:
fallthrough
case hErr == errFileNotFound, hErr == errVolumeNotFound:
dataErrs[i] = hErr
break
case hErr != nil:
logger.LogIf(ctx, hErr)
dataErrs[i] = hErr
break
}
}
if dataErrs[i] == nil {
// All parts verified, mark it as all data available.
availableDisks[i] = onlineDisk
}
}
return availableDisks, dataErrs
}