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b7049032a0
* Adds methods to schedule.Schedule to show the raw cron string and timezone * Uses these methods to clean up output of auto(start|stop) show or ls * Defaults CRON_TZ=UTC if not provided
122 lines
3.6 KiB
Go
122 lines
3.6 KiB
Go
// package schedule provides utilities for parsing and deserializing
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// cron-style expressions.
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package schedule
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import (
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"strings"
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"time"
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"github.com/robfig/cron/v3"
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"golang.org/x/xerrors"
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)
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// For the purposes of this library, we only need minute, hour, and
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// day-of-week. However to ensure interoperability we will use the standard
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// five-valued cron format. Descriptors are not supported.
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const parserFormat = cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow
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var defaultParser = cron.NewParser(parserFormat)
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// Weekly parses a Schedule from spec scoped to a recurring weekly event.
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// Spec consists of the following space-delimited fields, in the following order:
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// - timezone e.g. CRON_TZ=US/Central (optional)
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// - minutes of hour e.g. 30 (required)
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// - hour of day e.g. 9 (required)
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// - day of month (must be *)
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// - month (must be *)
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// - day of week e.g. 1 (required)
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//
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// Example Usage:
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// local_sched, _ := schedule.Weekly("59 23 *")
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// fmt.Println(sched.Next(time.Now().Format(time.RFC3339)))
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// // Output: 2022-04-04T23:59:00Z
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//
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// us_sched, _ := schedule.Weekly("CRON_TZ=US/Central 30 9 1-5")
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// fmt.Println(sched.Next(time.Now()).Format(time.RFC3339))
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// // Output: 2022-04-04T14:30:00Z
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func Weekly(raw string) (*Schedule, error) {
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if err := validateWeeklySpec(raw); err != nil {
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return nil, xerrors.Errorf("validate weekly schedule: %w", err)
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}
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// If schedule does not specify a timezone, default to UTC. Otherwise,
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// the library will default to time.Local which we want to avoid.
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if !strings.HasPrefix(raw, "CRON_TZ=") {
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raw = "CRON_TZ=UTC " + raw
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}
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specSched, err := defaultParser.Parse(raw)
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if err != nil {
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return nil, xerrors.Errorf("parse schedule: %w", err)
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}
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schedule, ok := specSched.(*cron.SpecSchedule)
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if !ok {
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return nil, xerrors.Errorf("expected *cron.SpecSchedule but got %T", specSched)
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}
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// Strip the leading CRON_TZ prefix so we just store the cron string.
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// The timezone info is available in SpecSchedule.
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cronStr := raw
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if strings.HasPrefix(raw, "CRON_TZ=") {
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cronStr = strings.Join(strings.Fields(raw)[1:], " ")
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}
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cronSched := &Schedule{
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sched: schedule,
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cronStr: cronStr,
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}
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return cronSched, nil
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}
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// Schedule represents a cron schedule.
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// It's essentially a thin wrapper for robfig/cron/v3 that implements Stringer.
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type Schedule struct {
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sched *cron.SpecSchedule
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// XXX: there isn't any nice way for robfig/cron to serialize
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cronStr string
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}
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// String serializes the schedule to its original human-friendly format.
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// The leading CRON_TZ is maintained.
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func (s Schedule) String() string {
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var sb strings.Builder
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_, _ = sb.WriteString("CRON_TZ=")
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_, _ = sb.WriteString(s.sched.Location.String())
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_, _ = sb.WriteString(" ")
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_, _ = sb.WriteString(s.cronStr)
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return sb.String()
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}
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// Timezone returns the timezone for the schedule.
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func (s Schedule) Timezone() string {
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return s.sched.Location.String()
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}
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// Cron returns the cron spec for the schedule with the leading CRON_TZ
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// stripped, if present.
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func (s Schedule) Cron() string {
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return s.cronStr
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}
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// Next returns the next time in the schedule relative to t.
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func (s Schedule) Next(t time.Time) time.Time {
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return s.sched.Next(t)
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}
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// validateWeeklySpec ensures that the day-of-month and month options of
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// spec are both set to *
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func validateWeeklySpec(spec string) error {
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parts := strings.Fields(spec)
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if len(parts) < 5 {
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return xerrors.Errorf("expected schedule to consist of 5 fields with an optional CRON_TZ=<timezone> prefix")
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}
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if len(parts) == 6 {
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parts = parts[1:]
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}
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if parts[2] != "*" || parts[3] != "*" {
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return xerrors.Errorf("expected month and dom to be *")
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}
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return nil
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}
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