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minio/cmd/erasure-metadata-utils.go

232 lines
7.2 KiB

/*
* MinIO Cloud Storage, (C) 2016-2019 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"
"errors"
"hash/crc32"
"github.com/minio/minio/cmd/logger"
"github.com/minio/minio/pkg/sync/errgroup"
)
// Returns number of errors that occurred the most (incl. nil) and the
// corresponding error value. NB When there is more than one error value that
// occurs maximum number of times, the error value returned depends on how
// golang's map orders keys. This doesn't affect correctness as long as quorum
// value is greater than or equal to simple majority, since none of the equally
// maximal values would occur quorum or more number of times.
func reduceErrs(errs []error, ignoredErrs []error) (maxCount int, maxErr error) {
errorCounts := make(map[error]int)
for _, err := range errs {
if IsErrIgnored(err, ignoredErrs...) {
continue
}
errorCounts[err]++
}
max := 0
for err, count := range errorCounts {
switch {
case max < count:
max = count
maxErr = err
// Prefer `nil` over other error values with the same
// number of occurrences.
case max == count && err == nil:
maxErr = err
}
}
return max, maxErr
}
// reduceQuorumErrs behaves like reduceErrs by only for returning
// values of maximally occurring errors validated against a generic
// quorum number that can be read or write quorum depending on usage.
func reduceQuorumErrs(ctx context.Context, errs []error, ignoredErrs []error, quorum int, quorumErr error) error {
maxCount, maxErr := reduceErrs(errs, ignoredErrs)
if maxCount >= quorum {
return maxErr
}
return quorumErr
}
// reduceReadQuorumErrs behaves like reduceErrs but only for returning
// values of maximally occurring errors validated against readQuorum.
func reduceReadQuorumErrs(ctx context.Context, errs []error, ignoredErrs []error, readQuorum int) (maxErr error) {
return reduceQuorumErrs(ctx, errs, ignoredErrs, readQuorum, errErasureReadQuorum)
}
// reduceWriteQuorumErrs behaves like reduceErrs but only for returning
// values of maximally occurring errors validated against writeQuorum.
func reduceWriteQuorumErrs(ctx context.Context, errs []error, ignoredErrs []error, writeQuorum int) (maxErr error) {
return reduceQuorumErrs(ctx, errs, ignoredErrs, writeQuorum, errErasureWriteQuorum)
}
// Similar to 'len(slice)' but returns the actual elements count
// skipping the unallocated elements.
func diskCount(disks []StorageAPI) int {
diskCount := 0
for _, disk := range disks {
if disk == nil {
continue
}
diskCount++
}
return diskCount
}
// hashOrder - hashes input key to return consistent
// hashed integer slice. Returned integer order is salted
// with an input key. This results in consistent order.
// NOTE: collisions are fine, we are not looking for uniqueness
// in the slices returned.
func hashOrder(key string, cardinality int) []int {
if cardinality <= 0 {
// Returns an empty int slice for cardinality < 0.
return nil
}
nums := make([]int, cardinality)
keyCrc := crc32.Checksum([]byte(key), crc32.IEEETable)
start := int(keyCrc % uint32(cardinality))
for i := 1; i <= cardinality; i++ {
nums[i-1] = 1 + ((start + i) % cardinality)
}
return nums
}
// Reads all `xl.meta` metadata as a FileInfo slice.
// Returns error slice indicating the failed metadata reads.
func readAllFileInfo(ctx context.Context, disks []StorageAPI, bucket, object, versionID string) ([]FileInfo, []error) {
metadataArray := make([]FileInfo, len(disks))
g := errgroup.WithNErrs(len(disks))
// Read `xl.meta` parallelly across disks.
for index := range disks {
index := index
g.Go(func() (err error) {
if disks[index] == nil {
return errDiskNotFound
}
metadataArray[index], err = disks[index].ReadVersion(bucket, object, versionID)
if err != nil {
if err != errFileNotFound && err != errVolumeNotFound && err != errFileVersionNotFound {
logger.GetReqInfo(ctx).AppendTags("disk", disks[index].String())
logger.LogIf(ctx, err)
}
}
return err
}, index)
}
// Return all the metadata.
return metadataArray, g.Wait()
}
// Return shuffled partsMetadata depending on distribution.
func shufflePartsMetadata(partsMetadata []FileInfo, distribution []int) (shuffledPartsMetadata []FileInfo) {
if distribution == nil {
return partsMetadata
}
shuffledPartsMetadata = make([]FileInfo, len(partsMetadata))
// Shuffle slice xl metadata for expected distribution.
for index := range partsMetadata {
blockIndex := distribution[index]
shuffledPartsMetadata[blockIndex-1] = partsMetadata[index]
}
return shuffledPartsMetadata
}
// shuffleDisks - shuffle input disks slice depending on the
// erasure distribution. Return shuffled slice of disks with
// their expected distribution.
func shuffleDisks(disks []StorageAPI, distribution []int) (shuffledDisks []StorageAPI) {
if distribution == nil {
return disks
}
shuffledDisks = make([]StorageAPI, len(disks))
// Shuffle disks for expected distribution.
for index := range disks {
blockIndex := distribution[index]
shuffledDisks[blockIndex-1] = disks[index]
}
return shuffledDisks
}
// evalDisks - returns a new slice of disks where nil is set if
// the corresponding error in errs slice is not nil
func evalDisks(disks []StorageAPI, errs []error) []StorageAPI {
if len(errs) != len(disks) {
logger.LogIf(GlobalContext, errors.New("unexpected disks/errors slice length"))
return nil
}
newDisks := make([]StorageAPI, len(disks))
for index := range errs {
if errs[index] == nil {
newDisks[index] = disks[index]
} else {
newDisks[index] = nil
}
}
return newDisks
}
// Errors specifically generated by calculatePartSizeFromIdx function.
var (
errPartSizeZero = errors.New("Part size cannot be zero")
errPartSizeIndex = errors.New("Part index cannot be smaller than 1")
)
// calculatePartSizeFromIdx calculates the part size according to input index.
// returns error if totalSize is -1, partSize is 0, partIndex is 0.
func calculatePartSizeFromIdx(ctx context.Context, totalSize int64, partSize int64, partIndex int) (currPartSize int64, err error) {
if totalSize < -1 {
logger.LogIf(ctx, errInvalidArgument)
return 0, errInvalidArgument
}
if partSize == 0 {
logger.LogIf(ctx, errPartSizeZero)
return 0, errPartSizeZero
}
if partIndex < 1 {
logger.LogIf(ctx, errPartSizeIndex)
return 0, errPartSizeIndex
}
if totalSize == -1 {
return -1, nil
}
if totalSize > 0 {
// Compute the total count of parts
partsCount := totalSize/partSize + 1
// Return the part's size
switch {
case int64(partIndex) < partsCount:
currPartSize = partSize
case int64(partIndex) == partsCount:
// Size of last part
currPartSize = totalSize % partSize
default:
currPartSize = 0
}
}
return currPartSize, nil
}