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minio/xl-v1-utils.go

135 lines
4.0 KiB

/*
* Minio Cloud Storage, (C) 2016 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 main
import (
"encoding/json"
"hash/crc32"
"path"
)
// Returns number of errors that occurred the most (incl. nil) and the
// corresponding error value. N B 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) error {
errorCounts := make(map[error]int)
for _, err := range errs {
if isErrIgnored(err, ignoredErrs) {
continue
}
errorCounts[err]++
}
max := 0
var errMax error
for err, count := range errorCounts {
if max < count {
max = count
errMax = err
}
}
return errMax
}
// Validates if we have quorum based on the errors related to disk only.
// Returns 'true' if we have quorum, 'false' if we don't.
func isDiskQuorum(errs []error, minQuorumCount int) bool {
var count int
for _, err := range errs {
switch err {
case errDiskNotFound, errFaultyDisk, errDiskAccessDenied:
continue
}
count++
}
return count >= minQuorumCount
}
// 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 returns 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 negative cardinality.
return nil
}
nums := make([]int, cardinality)
keyCrc := crc32.Checksum([]byte(key), crc32.IEEETable)
start := int(uint32(keyCrc)%uint32(cardinality)) | 1
for i := 1; i <= cardinality; i++ {
nums[i-1] = 1 + ((start + i) % cardinality)
}
return nums
}
// readXLMeta reads `xl.json` and returns back XL metadata structure.
func readXLMeta(disk StorageAPI, bucket string, object string) (xlMeta xlMetaV1, err error) {
// Reads entire `xl.json`.
buf, err := disk.ReadAll(bucket, path.Join(object, xlMetaJSONFile))
if err != nil {
return xlMetaV1{}, err
}
// Unmarshal xl metadata.
if err = json.Unmarshal(buf, &xlMeta); err != nil {
return xlMetaV1{}, err
}
// Return structured `xl.json`.
return xlMeta, nil
}
// Return ordered partsMetadata depeinding on distribution.
func getOrderedPartsMetadata(distribution []int, partsMetadata []xlMetaV1) (orderedPartsMetadata []xlMetaV1) {
orderedPartsMetadata = make([]xlMetaV1, len(partsMetadata))
for index := range partsMetadata {
blockIndex := distribution[index]
orderedPartsMetadata[blockIndex-1] = partsMetadata[index]
}
return orderedPartsMetadata
}
// getOrderedDisks - get ordered disks from erasure distribution.
// returns ordered slice of disks from their actual distribution.
func getOrderedDisks(distribution []int, disks []StorageAPI) (orderedDisks []StorageAPI) {
orderedDisks = make([]StorageAPI, len(disks))
// From disks gets ordered disks.
for index := range disks {
blockIndex := distribution[index]
orderedDisks[blockIndex-1] = disks[index]
}
return orderedDisks
}