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snapshot.go
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snapshot.go
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// Copyright 2019 xgfone
//
// 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 gconf
import (
"encoding/json"
"fmt"
"io/ioutil"
"os"
"reflect"
"sync"
"time"
)
// LoadBackupFile loads configuration data from the backup file if exists,
// then watches the change of the options and write them into the file.
//
// So you can use it as the local cache.
func (c *Config) LoadBackupFile(filename string) error {
var data []byte
var ms map[string]interface{}
if _, err := os.Stat(filename); err != nil {
if !os.IsNotExist(err) {
return err
}
} else if data, err = ioutil.ReadFile(filename); err != nil {
return err
} else if err = json.Unmarshal(data, &ms); err != nil {
return err
}
c.snap.InitMap(ms)
c.LoadMap(ms, false)
go c.writeSnapshotIntoFile(filename)
return nil
}
func (c *Config) writeSnapshotIntoFile(filename string) {
var lastgen uint64
ticker := time.NewTicker(time.Minute)
for {
select {
case _, ok := <-c.exit:
if !ok {
return
}
case <-ticker.C:
gen, data, err := c.snap.getData()
if err != nil {
c.handleError(fmt.Errorf("[Config] snapshot marshal json: %s", err.Error()))
} else if gen == lastgen {
continue
}
if err = ioutil.WriteFile(filename, data, os.ModePerm); err != nil {
c.handleError(fmt.Errorf("[Config] snapshot write file[%s]: %s", filename, err.Error()))
} else {
lastgen = gen
debugf("[Config] Write snapshot into file '%s'", filename)
}
}
}
}
// Snapshot returns the snapshot of the whole configuration options
// excpet for the their default values.
//
// Notice: the key includes the group name and the option name, for instance,
//
// map[string]interface{} {
// "opt1": "value1",
// "opt2": "value2",
// "group1.opt3": "value3",
// "group1.group2.opt4": "value4",
// // ...
// }
func (c *Config) Snapshot() map[string]interface{} {
return c.snap.ToMap()
}
func newSnapshot(c *Config) *snapshot {
snap := &snapshot{conf: c, maps: make(map[string]interface{}, 64)}
c.Observe(snap.ChangeObserver)
return snap
}
type snapshot struct {
conf *Config
lock sync.RWMutex
maps map[string]interface{}
gen uint64
}
func (s *snapshot) InitMap(ms map[string]interface{}) {
s.lock.Lock()
for k, v := range ms {
s.maps[k] = v
}
s.lock.Unlock()
}
func (s *snapshot) ToMap() map[string]interface{} {
s.lock.RLock()
dst := make(map[string]interface{}, len(s.maps)*2)
for key, value := range s.maps {
dst[key] = value
}
s.lock.RUnlock()
return dst
}
func (s *snapshot) ChangeObserver(group, opt string, old, new interface{}) {
key := opt
if group != "" {
key = fmt.Sprintf("%s%s%s", group, s.conf.gsep, opt)
}
s.lock.Lock()
defer s.lock.Unlock()
if value, ok := s.maps[key]; !ok || !reflect.DeepEqual(value, new) {
s.gen++
s.maps[key] = new
}
}
func (s *snapshot) getData() (uint64, []byte, error) {
s.lock.RLock()
defer s.lock.RUnlock()
data, err := json.Marshal(s.maps)
return s.gen, data, err
}