minio/xl-v1-utils.go
2016-07-13 11:56:25 -07:00

145 lines
4.3 KiB
Go

/*
* 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"
"errors"
"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) (int, error) {
errorCounts := make(map[error]int)
for _, err := range errs {
errorCounts[err]++
}
max := 0
var errMax error
for err, count := range errorCounts {
if max < count {
max = count
errMax = err
}
}
return max, 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 - returns consistent hashed integers of count slice, based on the input token.
func hashOrder(token string, count int) []int {
if count < 0 {
panic(errors.New("hashOrder count cannot be negative"))
}
nums := make([]int, count)
tokenCrc := crc32.Checksum([]byte(token), crc32.IEEETable)
start := int(uint32(tokenCrc)%uint32(count)) | 1
for i := 1; i <= count; i++ {
nums[i-1] = 1 + ((start + i) % count)
}
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
}
// Uses a map to find union of checksums of parts that were concurrently written
// but committed before this part. N B For a different, concurrent upload of
// the same part, the ongoing request's data/metadata prevails.
// cur - corresponds to parts written to disk before the ongoing putObjectPart request
// updated - corresponds to parts written to disk while the ongoing putObjectPart is in progress
// curPartName - name of the part that is being written
// returns []checkSumInfo containing the set union of checksums of parts that
// have been written so far incl. the part being written.
func unionChecksumInfos(cur []checkSumInfo, updated []checkSumInfo, curPartName string) []checkSumInfo {
checksumSet := make(map[string]checkSumInfo)
var checksums []checkSumInfo
checksums = cur
for _, cksum := range checksums {
checksumSet[cksum.Name] = cksum
}
checksums = updated
for _, cksum := range checksums {
// skip updating checksum of the part that is
// written in this request because the checksum
// from cur, corresponding to this part,
// should remain.
if cksum.Name == curPartName {
continue
}
checksumSet[cksum.Name] = cksum
}
// Form the checksumInfo to be committed in xl.json
// from the map.
var finalChecksums []checkSumInfo
for _, cksum := range checksumSet {
finalChecksums = append(finalChecksums, cksum)
}
return finalChecksums
}