/
snapshot_policy.go
194 lines (164 loc) · 4.36 KB
/
snapshot_policy.go
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package restic
import (
"fmt"
"reflect"
"sort"
"strings"
"time"
)
// ExpirePolicy configures which snapshots should be automatically removed.
type ExpirePolicy struct {
Last int // keep the last n snapshots
Hourly int // keep the last n hourly snapshots
Daily int // keep the last n daily snapshots
Weekly int // keep the last n weekly snapshots
Monthly int // keep the last n monthly snapshots
Yearly int // keep the last n yearly snapshots
Within Duration // keep snapshots made within this duration
Tags []TagList // keep all snapshots that include at least one of the tag lists.
}
func (e ExpirePolicy) String() (s string) {
var keeps []string
if e.Last > 0 {
keeps = append(keeps, fmt.Sprintf("%d snapshots", e.Last))
}
if e.Hourly > 0 {
keeps = append(keeps, fmt.Sprintf("%d hourly", e.Hourly))
}
if e.Daily > 0 {
keeps = append(keeps, fmt.Sprintf("%d daily", e.Daily))
}
if e.Weekly > 0 {
keeps = append(keeps, fmt.Sprintf("%d weekly", e.Weekly))
}
if e.Monthly > 0 {
keeps = append(keeps, fmt.Sprintf("%d monthly", e.Monthly))
}
if e.Yearly > 0 {
keeps = append(keeps, fmt.Sprintf("%d yearly", e.Yearly))
}
if len(keeps) > 0 {
s = fmt.Sprintf("keep the last %s snapshots", strings.Join(keeps, ", "))
}
if len(e.Tags) > 0 {
if s != "" {
s += " and "
}
s += fmt.Sprintf("all snapshots with tags %s", e.Tags)
}
if !e.Within.Zero() {
if s != "" {
s += " and "
}
s += fmt.Sprintf("all snapshots within %s of the newest", e.Within)
}
return s
}
// Sum returns the maximum number of snapshots to be kept according to this
// policy.
func (e ExpirePolicy) Sum() int {
return e.Last + e.Hourly + e.Daily + e.Weekly + e.Monthly + e.Yearly
}
// Empty returns true iff no policy has been configured (all values zero).
func (e ExpirePolicy) Empty() bool {
if len(e.Tags) != 0 {
return false
}
empty := ExpirePolicy{Tags: e.Tags}
return reflect.DeepEqual(e, empty)
}
// ymdh returns an integer in the form YYYYMMDDHH.
func ymdh(d time.Time, _ int) int {
return d.Year()*1000000 + int(d.Month())*10000 + d.Day()*100 + d.Hour()
}
// ymd returns an integer in the form YYYYMMDD.
func ymd(d time.Time, _ int) int {
return d.Year()*10000 + int(d.Month())*100 + d.Day()
}
// yw returns an integer in the form YYYYWW, where WW is the week number.
func yw(d time.Time, _ int) int {
year, week := d.ISOWeek()
return year*100 + week
}
// ym returns an integer in the form YYYYMM.
func ym(d time.Time, _ int) int {
return d.Year()*100 + int(d.Month())
}
// y returns the year of d.
func y(d time.Time, _ int) int {
return d.Year()
}
// always returns a unique number for d.
func always(d time.Time, nr int) int {
return nr
}
// findLatestTimestamp returns the time stamp for the newest snapshot.
func findLatestTimestamp(list Snapshots) time.Time {
if len(list) == 0 {
panic("list of snapshots is empty")
}
var latest time.Time
for _, sn := range list {
if sn.Time.After(latest) {
latest = sn.Time
}
}
return latest
}
// ApplyPolicy returns the snapshots from list that are to be kept and removed
// according to the policy p. list is sorted in the process.
func ApplyPolicy(list Snapshots, p ExpirePolicy) (keep, remove Snapshots) {
sort.Sort(list)
if p.Empty() {
return list, remove
}
if len(list) == 0 {
return list, remove
}
var buckets = [6]struct {
Count int
bucker func(d time.Time, nr int) int
Last int
}{
{p.Last, always, -1},
{p.Hourly, ymdh, -1},
{p.Daily, ymd, -1},
{p.Weekly, yw, -1},
{p.Monthly, ym, -1},
{p.Yearly, y, -1},
}
latest := findLatestTimestamp(list)
for nr, cur := range list {
var keepSnap bool
// Tags are handled specially as they are not counted.
for _, l := range p.Tags {
if cur.HasTags(l) {
keepSnap = true
}
}
// If the timestamp of the snapshot is within the range, then keep it.
if !p.Within.Zero() {
t := latest.AddDate(-p.Within.Years, -p.Within.Months, -p.Within.Days)
if cur.Time.After(t) {
keepSnap = true
}
}
// Now update the other buckets and see if they have some counts left.
for i, b := range buckets {
if b.Count > 0 {
val := b.bucker(cur.Time, nr)
if val != b.Last {
keepSnap = true
buckets[i].Last = val
buckets[i].Count--
}
}
}
if keepSnap {
keep = append(keep, cur)
} else {
remove = append(remove, cur)
}
}
return keep, remove
}