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Copy pathformat-fs.go
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259 lines (234 loc) · 7.33 KB
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/*
* Minio Cloud Storage, (C) 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 (
"fmt"
"io"
"os"
"path"
"time"
errors2 "github.com/minio/minio/pkg/errors"
"github.com/minio/minio/pkg/lock"
)
// FS format version strings.
const (
formatBackendFS = "fs"
formatFSVersionV1 = "1"
formatFSVersionV2 = "2"
)
// formatFSV1 - structure holds format version '1'.
type formatFSV1 struct {
formatMetaV1
FS struct {
Version string `json:"version"`
} `json:"fs"`
}
// formatFSV2 - structure is same as formatFSV1. But the multipart backend
// structure is flat instead of hierarchy now.
// In .minio.sys/multipart we have:
// sha256(bucket/object)/uploadID/[fs.json, 1.etag, 2.etag ....]
type formatFSV2 = formatFSV1
// Used to detect the version of "fs" format.
type formatFSVersionDetect struct {
FS struct {
Version string `json:"version"`
} `json:"fs"`
}
// Returns the latest "fs" format V1
func newFormatFSV1() (format *formatFSV1) {
f := &formatFSV1{}
f.Version = formatMetaVersionV1
f.Format = formatBackendFS
f.FS.Version = formatFSVersionV1
return f
}
// Returns the latest "fs" format V2
func newFormatFSV2() (format *formatFSV2) {
f := &formatFSV2{}
f.Version = formatMetaVersionV1
f.Format = formatBackendFS
f.FS.Version = formatFSVersionV2
return f
}
// Returns the field formatMetaV1.Format i.e the string "fs" which is never likely to change.
// We do not use this function in XL to get the format as the file is not fcntl-locked on XL.
func formatMetaGetFormatBackendFS(r io.ReadSeeker) (string, error) {
format := &formatMetaV1{}
if err := jsonLoad(r, format); err != nil {
return "", err
}
if format.Version == formatMetaVersionV1 {
return format.Format, nil
}
return "", fmt.Errorf(`format.Version expected: %s, got: %s`, formatMetaVersionV1, format.Version)
}
// Returns formatFS.FS.Version
func formatFSGetVersion(r io.ReadSeeker) (string, error) {
format := &formatFSVersionDetect{}
if err := jsonLoad(r, format); err != nil {
return "", err
}
return format.FS.Version, nil
}
// Migrate from V1 to V2. V2 implements new backend format for multipart
// uploads. Delete the previous multipart directory.
func formatFSMigrateV1ToV2(wlk *lock.LockedFile, fsPath string) error {
version, err := formatFSGetVersion(wlk)
if err != nil {
return err
}
if version != formatFSVersionV1 {
return fmt.Errorf(`format.json version expected %s, found %s`, formatFSVersionV1, version)
}
if err = fsRemoveAll(path.Join(fsPath, minioMetaMultipartBucket)); err != nil {
return err
}
if err = os.MkdirAll(path.Join(fsPath, minioMetaMultipartBucket), 0755); err != nil {
return err
}
return jsonSave(wlk.File, newFormatFSV2())
}
// Migrate the "fs" backend.
// Migration should happen when formatFSV1.FS.Version changes. This version
// can change when there is a change to the struct formatFSV1.FS or if there
// is any change in the backend file system tree structure.
func formatFSMigrate(wlk *lock.LockedFile, fsPath string) error {
// Add any migration code here in case we bump format.FS.Version
version, err := formatFSGetVersion(wlk)
if err != nil {
return err
}
switch version {
case formatFSVersionV1:
if err = formatFSMigrateV1ToV2(wlk, fsPath); err != nil {
return err
}
fallthrough
case formatFSVersionV2:
// We are at the latest version.
}
// Make sure that the version is what we expect after the migration.
version, err = formatFSGetVersion(wlk)
if err != nil {
return err
}
if version != formatFSVersionV2 {
return fmt.Errorf(`%s file: expected FS version: %s, found FS version: %s`, formatConfigFile, formatFSVersionV2, version)
}
return nil
}
// Creates a new format.json if unformatted.
func createFormatFS(fsFormatPath string) error {
// Attempt a write lock on formatConfigFile `format.json`
// file stored in minioMetaBucket(.minio.sys) directory.
lk, err := lock.TryLockedOpenFile(fsFormatPath, os.O_RDWR|os.O_CREATE, 0600)
if err != nil {
return errors2.Trace(err)
}
// Close the locked file upon return.
defer lk.Close()
fi, err := lk.Stat()
if err != nil {
return errors2.Trace(err)
}
if fi.Size() != 0 {
// format.json already got created because of another minio process's createFormatFS()
return nil
}
return jsonSave(lk.File, newFormatFSV1())
}
// This function returns a read-locked format.json reference to the caller.
// The file descriptor should be kept open throughout the life
// of the process so that another minio process does not try to
// migrate the backend when we are actively working on the backend.
func initFormatFS(fsPath string) (rlk *lock.RLockedFile, err error) {
fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
// Any read on format.json should be done with read-lock.
// Any write on format.json should be done with write-lock.
for {
isEmpty := false
rlk, err := lock.RLockedOpenFile(fsFormatPath)
if err == nil {
// format.json can be empty in a rare condition when another
// minio process just created the file but could not hold lock
// and write to it.
var fi os.FileInfo
fi, err = rlk.Stat()
if err != nil {
return nil, errors2.Trace(err)
}
isEmpty = fi.Size() == 0
}
if os.IsNotExist(err) || isEmpty {
if err == nil {
rlk.Close()
}
// Fresh disk - create format.json
err = createFormatFS(fsFormatPath)
if err == lock.ErrAlreadyLocked {
// Lock already present, sleep and attempt again.
// Can happen in a rare situation when a parallel minio process
// holds the lock and creates format.json
time.Sleep(100 * time.Millisecond)
continue
}
if err != nil {
return nil, errors2.Trace(err)
}
// After successfully creating format.json try to hold a read-lock on
// the file.
continue
}
if err != nil {
return nil, errors2.Trace(err)
}
formatBackend, err := formatMetaGetFormatBackendFS(rlk)
if err != nil {
return nil, errors2.Trace(err)
}
if formatBackend != formatBackendFS {
return nil, fmt.Errorf(`%s file: expected format-type: %s, found: %s`, formatConfigFile, formatBackendFS, formatBackend)
}
version, err := formatFSGetVersion(rlk)
if err != nil {
return nil, err
}
if version != formatFSVersionV2 {
// Format needs migration
rlk.Close()
// Hold write lock during migration so that we do not disturb any
// minio processes running in parallel.
wlk, err := lock.TryLockedOpenFile(fsFormatPath, os.O_RDWR, 0)
if err == lock.ErrAlreadyLocked {
// Lock already present, sleep and attempt again.
time.Sleep(100 * time.Millisecond)
continue
}
if err != nil {
return nil, err
}
err = formatFSMigrate(wlk, fsPath)
wlk.Close()
if err != nil {
// Migration failed, bail out so that the user can observe what happened.
return nil, err
}
// Successfully migrated, now try to hold a read-lock on format.json
continue
}
return rlk, nil
}
}