minio/cmd/xl-v1-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"
"github.com/minio/minio/pkg/sync/errgroup"
)
// getLoadBalancedDisks - fetches load balanced (sufficiently randomized) disk slice.
func (xl xlObjects) getLoadBalancedDisks() (disks []StorageAPI) {
// Based on the random shuffling return back randomized disks.
for _, i := range hashOrder(UTCNow().String(), len(xl.getDisks())) {
disks = append(disks, xl.getDisks()[i-1])
}
return disks
}
// This function does the following check, suppose
// object is "a/b/c/d", stat makes sure that objects ""a/b/c""
// "a/b" and "a" do not exist.
func (xl xlObjects) parentDirIsObject(ctx context.Context, bucket, parent string) bool {
var isParentDirObject func(string) bool
isParentDirObject = func(p string) bool {
if p == "." || p == SlashSeparator {
return false
}
if xl.isObject(bucket, p) {
// If there is already a file at prefix "p", return true.
return true
}
// Check if there is a file as one of the parent paths.
return isParentDirObject(path.Dir(p))
}
return isParentDirObject(parent)
}
// isObject - returns `true` if the prefix is an object i.e if
// `xl.json` exists at the leaf, false otherwise.
func (xl xlObjects) isObject(bucket, prefix string) (ok bool) {
storageDisks := xl.getDisks()
g := errgroup.WithNErrs(len(storageDisks))
for index := range storageDisks {
index := index
g.Go(func() error {
if storageDisks[index] == nil {
return errDiskNotFound
}
// Check if 'prefix' is an object on this 'disk', else continue the check the next disk
fi, err := storageDisks[index].StatFile(bucket, pathJoin(prefix, xlMetaJSONFile))
if err != nil {
return err
}
if fi.Size == 0 {
return errCorruptedFormat
}
return nil
}, index)
}
// NOTE: Observe we are not trying to read `xl.json` and figure out the actual
// quorum intentionally, but rely on the default case scenario. Actual quorum
// verification will happen by top layer by using getObjectInfo() and will be
// ignored if necessary.
readQuorum := len(storageDisks) / 2
return reduceReadQuorumErrs(context.Background(), g.Wait(), objectOpIgnoredErrs, readQuorum) == nil
}