ledisdb/server/snapshot.go

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package server
import (
"fmt"
"github.com/siddontang/go/log"
"github.com/siddontang/ledisdb/config"
"io"
"io/ioutil"
"os"
"path"
"sort"
"sync"
"time"
)
const (
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snapshotTimeFormat = "2006-01-02T15:04:05.999999999"
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)
type snapshotStore struct {
sync.Mutex
cfg *config.Config
names []string
quit chan struct{}
}
func snapshotName(t time.Time) string {
return fmt.Sprintf("snap-%s.dump", t.Format(snapshotTimeFormat))
}
func parseSnapshotName(name string) (time.Time, error) {
var timeString string
if _, err := fmt.Sscanf(name, "snap-%s.dump", &timeString); err != nil {
return time.Time{}, err
}
when, err := time.Parse(snapshotTimeFormat, timeString)
if err != nil {
return time.Time{}, err
}
return when, nil
}
func newSnapshotStore(cfg *config.Config) (*snapshotStore, error) {
if len(cfg.Snapshot.Path) == 0 {
cfg.Snapshot.Path = path.Join(cfg.DataDir, "snapshot")
}
if err := os.MkdirAll(cfg.Snapshot.Path, 0755); err != nil {
return nil, err
}
s := new(snapshotStore)
s.cfg = cfg
s.names = make([]string, 0, s.cfg.Snapshot.MaxNum)
s.quit = make(chan struct{})
snapshots, err := ioutil.ReadDir(cfg.Snapshot.Path)
if err != nil {
return nil, err
}
for _, info := range snapshots {
if _, err := parseSnapshotName(info.Name()); err != nil {
log.Error("invalid snapshot file name %s, err: %s", info.Name(), err.Error())
continue
}
s.names = append(s.names, info.Name())
}
//from old to new
sort.Strings(s.names)
go s.run()
return s, nil
}
func (s *snapshotStore) Close() {
close(s.quit)
}
func (s *snapshotStore) run() {
t := time.NewTicker(1 * time.Minute)
defer t.Stop()
for {
select {
case <-t.C:
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s.Lock()
s.purge(false)
s.Unlock()
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case <-s.quit:
return
}
}
}
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func (s *snapshotStore) purge(create bool) {
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var names []string
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maxNum := s.cfg.Snapshot.MaxNum
num := len(s.names) - maxNum
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if create {
num++
if num > len(s.names) {
num = len(s.names)
}
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}
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if num > 0 {
names = s.names[0:num]
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n := copy(s.names, s.names[num:])
s.names = s.names[0:n]
}
for _, name := range names {
if err := os.Remove(s.snapshotPath(name)); err != nil {
log.Error("purge snapshot %s error %s", name, err.Error())
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}
}
}
func (s *snapshotStore) snapshotPath(name string) string {
return path.Join(s.cfg.Snapshot.Path, name)
}
type snapshotDumper interface {
Dump(w io.Writer) error
}
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type snapshot struct {
io.ReadCloser
f *os.File
}
func (st *snapshot) Read(b []byte) (int, error) {
return st.f.Read(b)
}
func (st *snapshot) Close() error {
return st.f.Close()
}
func (st *snapshot) Size() int64 {
s, _ := st.f.Stat()
return s.Size()
}
func (s *snapshotStore) Create(d snapshotDumper) (*snapshot, time.Time, error) {
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s.Lock()
defer s.Unlock()
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s.purge(true)
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now := time.Now()
name := snapshotName(now)
if len(s.names) > 0 && s.names[len(s.names)-1] >= name {
return nil, time.Time{}, fmt.Errorf("create snapshot file time %s is behind %s ", name, s.names[len(s.names)-1])
}
f, err := os.OpenFile(s.snapshotPath(name), os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
return nil, time.Time{}, err
}
if err := d.Dump(f); err != nil {
f.Close()
os.Remove(s.snapshotPath(name))
return nil, time.Time{}, err
}
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f.Sync()
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s.names = append(s.names, name)
f.Seek(0, os.SEEK_SET)
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return &snapshot{f: f}, now, nil
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}
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func (s *snapshotStore) OpenLatest() (*snapshot, time.Time, error) {
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s.Lock()
defer s.Unlock()
if len(s.names) == 0 {
return nil, time.Time{}, nil
}
name := s.names[len(s.names)-1]
t, _ := parseSnapshotName(name)
f, err := os.Open(s.snapshotPath(name))
if err != nil {
return nil, time.Time{}, err
}
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return &snapshot{f: f}, t, err
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}