cubefs

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// Copyright 2023 The CubeFS Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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// implied. See the License for the specific language governing
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// permissions and limitations under the License.
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package reloadconf
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import (
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	"bytes"
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	"crypto/md5"
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	"encoding/base64"
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	"fmt"
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	"os"
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	"sync"
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	"time"
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	"github.com/cubefs/cubefs/blobstore/util/errors"
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	"github.com/cubefs/cubefs/util/log"
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)
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// ReloadConf loads remote configuration change dynamically
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type ReloadConf struct {
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	ConfName      string
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	ReloadSec     int
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	RequestRemote func() ([]byte, error)
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	md5sum []byte
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	mutex  sync.Mutex
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}
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func (self *ReloadConf) reload(reload func(data []byte) error) error {
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	self.mutex.Lock()
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	defer self.mutex.Unlock()
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	// remote load
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	if self.RequestRemote != nil {
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		errRemote := self.remoteReload(reload)
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		if errRemote != nil {
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			log.LogWarn("remoteReload failed", self.ConfName, errors.Detail(errRemote))
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		} else {
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			return nil
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		}
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	}
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	// local load
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	errLocal := self.localReload(reload)
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	if errLocal != nil {
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		err := errors.Info(errLocal, "localReload").Detail(errLocal)
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		return err
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	}
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	return nil
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}
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func (self *ReloadConf) remoteReload(reload func(data []byte) error) (err error) {
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	data, md5sum, err := fetchRemote(self.RequestRemote)
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	if err != nil {
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		err = errors.Info(err, "fetchRemote").Detail(err)
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		return
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	}
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	// compare whether md5sum is changed
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	if bytes.Equal(md5sum, self.md5sum) {
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		log.LogDebug("remoteReload:", self.ConfName, "do nothing cause of md5sum is equal")
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		return nil
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	}
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	confName := fmt.Sprintf("%v_%v", self.ConfName, base64.URLEncoding.EncodeToString(md5sum))
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	err = os.WriteFile(confName, data, 0o666)
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	if err != nil {
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		err = errors.Info(err, "os.WriteFile")
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		return
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	}
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	log.LogInfof("remoteReload %v remote file is changed, oldmd5: %v, newmd5: %v", self.ConfName, self.md5sum, md5sum)
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	err = reload(data)
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	if err != nil {
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		os.Remove(confName)
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		err = errors.Info(err, "reload", confName).Detail(err)
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		return
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	}
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	err = os.Rename(confName, self.ConfName)
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	if err != nil {
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		os.Remove(confName)
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		err = errors.Info(err, "os.Rename")
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		return
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	}
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	self.md5sum = md5sum
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	return
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}
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func (self *ReloadConf) localReload(reload func(data []byte) error) (err error) {
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	data, err := os.ReadFile(self.ConfName)
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	if err != nil {
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		err = errors.Info(err, "os.ReadFile").Detail(err)
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		return
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	}
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	md5sum := calcMD5Sum(data)
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	if bytes.Equal(md5sum, self.md5sum) {
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		log.LogDebug("localReload:", self.ConfName, "do nothing cause of md5sum is equal")
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		return nil
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	}
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	log.LogInfof("localReload: %v local file is changed, oldmd5: %v, newmd5: %v", self.ConfName, self.md5sum, md5sum)
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	err = reload(data)
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	if err != nil {
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		err = errors.Info(err, "reload").Detail(err)
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		return
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	}
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	self.md5sum = md5sum
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	return
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}
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func fetchRemote(requestRemote func() ([]byte, error)) (data, md5sum []byte, err error) {
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	data, err = requestRemote()
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	if err != nil {
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		err = errors.Info(err, "io.ReadAll")
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		return
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	}
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	md5sum = calcMD5Sum(data)
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	return
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}
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func StartReload(cfg *ReloadConf, reload func(data []byte) error) (err error) {
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	err = cfg.reload(reload)
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	if err != nil {
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		log.LogError("cfg.reload:", cfg.ConfName, errors.Detail(err))
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		return
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	}
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	if cfg.ReloadSec == 0 {
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		return
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	}
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	go func() {
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		dur := time.Duration(cfg.ReloadSec) * time.Second
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		for range time.Tick(dur) {
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			err := cfg.reload(reload)
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			if err != nil {
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				log.LogError("cfg.reload:", cfg.ConfName, errors.Detail(err))
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			}
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		}
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	}()
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	return
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}
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func calcMD5Sum(b []byte) []byte {
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	h := md5.New()
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	h.Write(b)
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	return h.Sum(nil)
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}
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