cron

README

cron

A fast non-allocating cron parser in ragel and golang.

features

• standard five-position cron
• six-position cron with seconds
• seven-position cron with seconds and years
• case-insensitive days of the week
• case-insensitive month names
• Quartz compatible ranges e.g.: 4/10, SUN-THURS/2
• timezone handling (other than UTC)
• Quartz compatible # handling, i.e. 5#3 meaning the third friday of the month
• Quartz compatible L handling, i.e. 5L in the day of week field meaning the last friday of a month, or 3L in the day of month field meaning third to last day of the month

performance

On a 3.1 Ghz Core i7 MacBook Pro (Retina, 15-inch, Mid 2017):

BenchmarkParse/0_*_*_*_*_*_*-8	20000000	63.5 ns/op	0 B/op
BenchmarkParse/1-6/2_*_*_*_Feb-Oct/3_*_*-8	10000000	118 ns/op	0 B/op
BenchmarkParse/1-6/2_*_*_*_Feb-Oct/3_*_2020/4-8	1000000	146 ns/op	0 B/op

TODO

• Once we are done adding all of the Quartz cron features, to copy and pass all of Quartz's parsing tests.

Documentation

Index

• type Parsed
  • func ParseUTC(s string) (Parsed, error)
  • func (nt *Parsed) Count(from, to time.Time) (count int)
  • func (nt Parsed) Next(from time.Time) (time.Time, error)

Examples

• ParseUTC

Types

type Parsed

type Parsed struct {
	// contains filtered or unexported fields
}

Parsed is a parsed cron string. It can be used to find the next instance of a cron task.

func ParseUTC

func ParseUTC(s string) (Parsed, error)

ParseUTC parses a cron string in UTC timezone.

Example

package main

import (
	"fmt"
	"time"

	"github.com/influxdata/cron"
)

func main() {
	p, err := cron.ParseUTC("10 * * * * *")
	if err != nil {
		fmt.Println(err)
	}
	ts, err := p.Next(time.Date(1999, 12, 31, 23, 59, 59, 0, time.UTC))
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(ts)
}

Output:

2000-01-01 00:00:10 +0000 UTC

func (*Parsed) Count

func (nt *Parsed) Count(from, to time.Time) (count int)

Count gives us a count of the number of calls Parsed.Next would take to iterate though the time interval [from, to). We try to be O(1) where possible. However for periods longer than a month that don't use @every, it is worst case O(m) where m is the number of months in the interval.

func (Parsed) Next

func (nt Parsed) Next(from time.Time) (time.Time, error)

Next returns the next time a cron task should run given a Parsed cron string. It will error if the Parsed is not from a zero value.