Chain is a sequence of JobWrappers that decorates submitted jobs with cross-cutting behaviors like logging or synchronization.
type Chain struct {
// contains filtered or unexported fields
}
func NewChain(c ...JobWrapper) Chain
NewChain returns a Chain consisting of the given JobWrappers.
func (c Chain) Then(j Job) Job
Then decorates the given job with all JobWrappers in the chain.
This:
NewChain(m1, m2, m3).Then(job)
is equivalent to:
m1(m2(m3(job)))
ConstantDelaySchedule represents a simple recurring duty cycle, e.g. "Every 5 minutes". It does not support jobs more frequent than once a second.
type ConstantDelaySchedule struct {
Delay time.Duration
}
func Every(duration time.Duration) ConstantDelaySchedule
Every returns a crontab Schedule that activates once every duration. Delays of less than a second are not supported (will round up to 1 second). Any fields less than a Second are truncated.
func (schedule ConstantDelaySchedule) Next(t time.Time) time.Time
Next returns the next time this should be run. This rounds so that the next activation time will be on the second.
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 {
// contains filtered or unexported fields
}
func New(opts ...Option) *Cron
New returns a new Cron job runner, modified by the given options.
Available Settings
Time Zone Description: The time zone in which schedules are interpreted Default: time.Local Parser Description: Parser converts cron spec strings into cron.Schedules. Default: Accepts this spec: https://en.wikipedia.org/wiki/Cron Chain Description: Wrap submitted jobs to customize behavior. Default: A chain that recovers panics and logs them to stderr.
See "cron.With*" to modify the default behavior.
func (c *Cron) AddFunc(spec string, cmd func()) (EntryID, error)
AddFunc adds a func to the Cron to be run on the given schedule. The spec is parsed using the time zone of this Cron instance as the default. An opaque ID is returned that can be used to later remove it.
func (c *Cron) AddJob(spec string, cmd Job) (EntryID, error)
AddJob adds a Job to the Cron to be run on the given schedule. The spec is parsed using the time zone of this Cron instance as the default. An opaque ID is returned that can be used to later remove it.
func (c *Cron) Entries() []Entry
Entries returns a snapshot of the cron entries.
func (c *Cron) Entry(id EntryID) Entry
Entry returns a snapshot of the given entry, or nil if it couldn't be found.
func (c *Cron) Location() *time.Location
Location gets the time zone location
func (c *Cron) Remove(id EntryID)
Remove an entry from being run in the future.
func (c *Cron) Run()
Run the cron scheduler, or no-op if already running.
func (c *Cron) Schedule(schedule Schedule, cmd Job) EntryID
Schedule adds a Job to the Cron to be run on the given schedule. The job is wrapped with the configured Chain.
func (c *Cron) Start()
Start the cron scheduler in its own goroutine, or no-op if already started.
func (c *Cron) Stop() context.Context
Stop stops the cron scheduler if it is running; otherwise it does nothing. A context is returned so the caller can wait for running jobs to complete.
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
// WrappedJob is the thing to run when the Schedule is activated.
WrappedJob Job
// Job is the thing that was submitted to cron.
// It is kept around so that user code that needs to get at the job later,
// e.g. via Entries() can do so.
Job Job
}
func (e Entry) Valid() bool
Valid returns true if this is not the zero entry.
EntryID identifies an entry within a Cron instance
type EntryID int
FuncJob is a wrapper that turns a func() into a cron.Job
type FuncJob func()
func (f FuncJob) Run()
Job is an interface for submitted cron jobs.
type Job interface {
Run()
}
JobWrapper decorates the given Job with some behavior.
type JobWrapper func(Job) Job
func DelayIfStillRunning(logger Logger) JobWrapper
DelayIfStillRunning serializes jobs, delaying subsequent runs until the previous one is complete. Jobs running after a delay of more than a minute have the delay logged at Info.
func Recover(logger Logger) JobWrapper
Recover panics in wrapped jobs and log them with the provided logger.
func SkipIfStillRunning(logger Logger) JobWrapper
SkipIfStillRunning skips an invocation of the Job if a previous invocation is still running. It logs skips to the given logger at Info level.
Logger is the interface used in this package for logging, so that any backend can be plugged in. It is a subset of the github.com/go-logr/logr interface.
type Logger interface {
// Info logs routine messages about cron's operation.
Info(msg string, keysAndValues ...interface{})
// Error logs an error condition.
Error(err error, msg string, keysAndValues ...interface{})
}
DefaultLogger is used by Cron if none is specified.
var DefaultLogger Logger = PrintfLogger(log.New(os.Stdout, "cron: ", log.LstdFlags))
DiscardLogger can be used by callers to discard all log messages.
var DiscardLogger Logger = PrintfLogger(log.New(ioutil.Discard, "", 0))
func PrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger
PrintfLogger wraps a Printf-based logger (such as the standard library "log") into an implementation of the Logger interface which logs errors only.
func VerbosePrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger
VerbosePrintfLogger wraps a Printf-based logger (such as the standard library "log") into an implementation of the Logger interface which logs everything.
Option represents a modification to the default behavior of a Cron.
type Option func(*Cron)
func WithChain(wrappers ...JobWrapper) Option
WithChain specifies Job wrappers to apply to all jobs added to this cron. Refer to the Chain* functions in this package for provided wrappers.
func WithLocation(loc *time.Location) Option
WithLocation overrides the timezone of the cron instance.
func WithLogger(logger Logger) Option
WithLogger uses the provided logger.
func WithParser(p ScheduleParser) Option
WithParser overrides the parser used for interpreting job schedules.
func WithSeconds() Option
WithSeconds overrides the parser used for interpreting job schedules to include a seconds field as the first one.
Configuration options for creating a parser. Most options specify which fields should be included, while others enable features. If a field is not included the parser will assume a default value. These options do not change the order fields are parse in.
type ParseOption int
const (
Second ParseOption = 1 << iota // Seconds field, default 0
SecondOptional // Optional seconds field, default 0
Minute // Minutes field, default 0
Hour // Hours field, default 0
Dom // Day of month field, default *
Month // Month field, default *
Dow // Day of week field, default *
DowOptional // Optional day of week field, default *
Descriptor // Allow descriptors such as @monthly, @weekly, etc.
)
A custom Parser that can be configured.
type Parser struct {
// contains filtered or unexported fields
}
func NewParser(options ParseOption) Parser
NewParser creates a Parser with custom options.
It panics if more than one Optional is given, since it would be impossible to correctly infer which optional is provided or missing in general.
Examples
// Standard parser without descriptors
specParser := NewParser(Minute | Hour | Dom | Month | Dow)
sched, err := specParser.Parse("0 0 15 */3 *")
// Same as above, just excludes time fields
subsParser := NewParser(Dom | Month | Dow)
sched, err := specParser.Parse("15 */3 *")
// Same as above, just makes Dow optional
subsParser := NewParser(Dom | Month | DowOptional)
sched, err := specParser.Parse("15 */3")
func (p Parser) Parse(spec string) (Schedule, error)
Parse returns a new crontab schedule representing the given spec. It returns a descriptive error if the spec is not valid. It accepts crontab specs and features configured by NewParser.
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
}
func ParseStandard(standardSpec string) (Schedule, error)
ParseStandard returns a new crontab schedule representing the given standardSpec (https://en.wikipedia.org/wiki/Cron). It requires 5 entries representing: minute, hour, day of month, month and day of week, in that order. It returns a descriptive error if the spec is not valid.
It accepts
ScheduleParser is an interface for schedule spec parsers that return a Schedule
type ScheduleParser interface {
Parse(spec string) (Schedule, error)
}
SpecSchedule specifies a duty cycle (to the second granularity), based on a traditional crontab specification. It is computed initially and stored as bit sets.
type SpecSchedule struct {
Second, Minute, Hour, Dom, Month, Dow uint64
// Override location for this schedule.
Location *time.Location
}
func (s *SpecSchedule) Next(t time.Time) time.Time
Next returns the next time this schedule is activated, greater than the given time. If no time can be found to satisfy the schedule, return the zero time.