155 lines
3.6 KiB
Go
155 lines
3.6 KiB
Go
package crondaemon
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import (
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"context"
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"fmt"
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"sync"
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"sync/atomic"
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"github.com/robfig/cron"
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"github.com/sirupsen/logrus"
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)
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// runner defines the cron runner.
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type runner interface {
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Start()
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Stop()
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Schedule(cron.Schedule, cron.Job)
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}
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// RunFunc is the function that is run by the daemon on the schedule.
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type RunFunc func(context.Context) error
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// Daemon runs a runFunc on a cron schedule.
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type Daemon struct {
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mu sync.Mutex
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ctx context.Context // The context to pass on each run invocation.
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name string // The name of the daemon.
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run RunFunc // The function to run on the cron schedule.
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runner runner // The cron runner instance.
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newRunner func() runner // The function that instantiates a new cron runner.
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lastExp string // The last successfully applied cron expression.
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running bool // True if the daemon was successfully scheduled and is running.
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everScheduled bool // True if the daemon was ever scheduled.
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done chan struct{} // The channel that is closed when the daemon is disabled by passing an empty cron expression.
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runInProgress atomic.Bool // True if the run function is currently running.
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}
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// New creates a new daemon instance.
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func New(ctx context.Context, name string, run RunFunc) *Daemon {
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return &Daemon{
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ctx: ctx,
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name: name,
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run: run,
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newRunner: func() runner {
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return cron.New()
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},
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}
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}
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// Schedule the daemon with the new cron expression.
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// If the cron expression is empty, the daemon is stopped/disabled.
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// Subsequent calls with the same cron expression are no-op.
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// The daemon logs initial and all effective schedule calls using info level
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// and errors returned by the run function using error level.
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func (d *Daemon) Schedule(exp string) error {
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d.mu.Lock()
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defer d.mu.Unlock()
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if d.ctx.Err() != nil {
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return nil
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}
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if (!d.everScheduled || d.running) && exp == "" {
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d.everScheduled = true
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logrus.Info(d.withPrefix("daemon is disabled"))
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}
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if d.running && exp == d.lastExp ||
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!d.running && exp == "" {
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return nil
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}
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if exp == "" {
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if d.runner != nil {
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d.runner.Stop()
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}
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close(d.done)
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d.lastExp = ""
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d.running = false
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return nil
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}
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schedule, err := ParseCron(exp)
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if err != nil {
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return err
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}
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d.lastExp = exp
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d.everScheduled = true
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logrus.Info(d.withPrefix("daemon is scheduled with '" + exp + "'"))
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if d.runner != nil {
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d.runner.Stop()
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}
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d.runner = d.newRunner()
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d.runner.Schedule(schedule, cron.FuncJob(func() {
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if d.runInProgress.Load() {
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return // Skip if it the previous run is still in progress.
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}
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d.runInProgress.Store(true)
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defer d.runInProgress.Store(false)
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if err := d.run(d.ctx); err != nil {
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logrus.Error(d.withPrefix(err.Error()))
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}
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}))
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d.runner.Start()
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d.done = make(chan struct{})
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if !d.running {
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go func() {
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select {
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case <-d.done:
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return
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case <-d.ctx.Done():
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logrus.Info(d.withPrefix("context cancelled, stopping daemon"))
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d.mu.Lock()
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defer d.mu.Unlock()
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if d.runner != nil {
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d.runner.Stop()
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}
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}
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}()
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}
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d.running = true
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return nil
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}
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// withPrefix is a helper that adds the daemon name to log messages.
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func (d *Daemon) withPrefix(msg string) string {
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if d.name == "" {
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return msg
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}
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return d.name + ": " + msg
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}
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// ParseCron parses a cron expression.
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func ParseCron(exp string) (cron.Schedule, error) {
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if exp == "" {
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return nil, nil
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}
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schedule, err := cron.ParseStandard(exp)
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if err != nil {
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return nil, fmt.Errorf("error parsing cron: %w", err)
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}
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return schedule, nil
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}
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