k3s/vendor/gopkg.in/robfig/cron.v2/cron.go
2019-11-10 04:05:59 +00:00

237 lines
5.4 KiB
Go

// Package cron implements a cron spec parser and runner.
package cron // import "gopkg.in/robfig/cron.v2"
import (
"sort"
"time"
)
// Cron keeps track of any number of entries, invoking the associated func as
// specified by the schedule. It may be started, stopped, and the entries may
// be inspected while running.
type Cron struct {
entries []*Entry
stop chan struct{}
add chan *Entry
remove chan EntryID
snapshot chan []Entry
running bool
nextID EntryID
}
// Job is an interface for submitted cron jobs.
type Job interface {
Run()
}
// Schedule describes a job's duty cycle.
type Schedule interface {
// Next returns the next activation time, later than the given time.
// Next is invoked initially, and then each time the job is run.
Next(time.Time) time.Time
}
// EntryID identifies an entry within a Cron instance
type EntryID int
// Entry consists of a schedule and the func to execute on that schedule.
type Entry struct {
// ID is the cron-assigned ID of this entry, which may be used to look up a
// snapshot or remove it.
ID EntryID
// Schedule on which this job should be run.
Schedule Schedule
// Next time the job will run, or the zero time if Cron has not been
// started or this entry's schedule is unsatisfiable
Next time.Time
// Prev is the last time this job was run, or the zero time if never.
Prev time.Time
// Job is the thing to run when the Schedule is activated.
Job Job
}
// Valid returns true if this is not the zero entry.
func (e Entry) Valid() bool { return e.ID != 0 }
// byTime is a wrapper for sorting the entry array by time
// (with zero time at the end).
type byTime []*Entry
func (s byTime) Len() int { return len(s) }
func (s byTime) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s byTime) Less(i, j int) bool {
// Two zero times should return false.
// Otherwise, zero is "greater" than any other time.
// (To sort it at the end of the list.)
if s[i].Next.IsZero() {
return false
}
if s[j].Next.IsZero() {
return true
}
return s[i].Next.Before(s[j].Next)
}
// New returns a new Cron job runner.
func New() *Cron {
return &Cron{
entries: nil,
add: make(chan *Entry),
stop: make(chan struct{}),
snapshot: make(chan []Entry),
remove: make(chan EntryID),
running: false,
}
}
// FuncJob is a wrapper that turns a func() into a cron.Job
type FuncJob func()
func (f FuncJob) Run() { f() }
// AddFunc adds a func to the Cron to be run on the given schedule.
func (c *Cron) AddFunc(spec string, cmd func()) (EntryID, error) {
return c.AddJob(spec, FuncJob(cmd))
}
// AddJob adds a Job to the Cron to be run on the given schedule.
func (c *Cron) AddJob(spec string, cmd Job) (EntryID, error) {
schedule, err := Parse(spec)
if err != nil {
return 0, err
}
return c.Schedule(schedule, cmd), nil
}
// Schedule adds a Job to the Cron to be run on the given schedule.
func (c *Cron) Schedule(schedule Schedule, cmd Job) EntryID {
c.nextID++
entry := &Entry{
ID: c.nextID,
Schedule: schedule,
Job: cmd,
}
if !c.running {
c.entries = append(c.entries, entry)
} else {
c.add <- entry
}
return entry.ID
}
// Entries returns a snapshot of the cron entries.
func (c *Cron) Entries() []Entry {
if c.running {
c.snapshot <- nil
return <-c.snapshot
}
return c.entrySnapshot()
}
// Entry returns a snapshot of the given entry, or nil if it couldn't be found.
func (c *Cron) Entry(id EntryID) Entry {
for _, entry := range c.Entries() {
if id == entry.ID {
return entry
}
}
return Entry{}
}
// Remove an entry from being run in the future.
func (c *Cron) Remove(id EntryID) {
if c.running {
c.remove <- id
} else {
c.removeEntry(id)
}
}
// Start the cron scheduler in its own go-routine.
func (c *Cron) Start() {
c.running = true
go c.run()
}
// run the scheduler.. this is private just due to the need to synchronize
// access to the 'running' state variable.
func (c *Cron) run() {
// Figure out the next activation times for each entry.
now := time.Now().Local()
for _, entry := range c.entries {
entry.Next = entry.Schedule.Next(now)
}
for {
// Determine the next entry to run.
sort.Sort(byTime(c.entries))
var effective time.Time
if len(c.entries) == 0 || c.entries[0].Next.IsZero() {
// If there are no entries yet, just sleep - it still handles new entries
// and stop requests.
effective = now.AddDate(10, 0, 0)
} else {
effective = c.entries[0].Next
}
select {
case now = <-time.After(effective.Sub(now)):
// Run every entry whose next time was this effective time.
for _, e := range c.entries {
if e.Next != effective {
break
}
go e.Job.Run()
e.Prev = e.Next
e.Next = e.Schedule.Next(effective)
}
continue
case newEntry := <-c.add:
c.entries = append(c.entries, newEntry)
newEntry.Next = newEntry.Schedule.Next(now)
case <-c.snapshot:
c.snapshot <- c.entrySnapshot()
case id := <-c.remove:
c.removeEntry(id)
case <-c.stop:
return
}
now = time.Now().Local()
}
}
// Stop the cron scheduler.
func (c *Cron) Stop() {
c.stop <- struct{}{}
c.running = false
}
// entrySnapshot returns a copy of the current cron entry list.
func (c *Cron) entrySnapshot() []Entry {
var entries = make([]Entry, len(c.entries))
for i, e := range c.entries {
entries[i] = *e
}
return entries
}
func (c *Cron) removeEntry(id EntryID) {
var entries []*Entry
for _, e := range c.entries {
if e.ID != id {
entries = append(entries, e)
}
}
c.entries = entries
}