Add sync => go-sync

sync/cron.go

@@ -0,0 +1,93 @@
+package sync
+
+import (
+	"fmt"
+	"math"
+	"time"
+
+	"github.com/micro/go-log"
+	"github.com/micro/go-micro/sync/leader/consul"
+	"github.com/micro/go-micro/sync/task"
+	"github.com/micro/go-micro/sync/task/local"
+)
+
+type syncCron struct {
+	opts Options
+}
+
+func backoff(attempts int) time.Duration {
+	if attempts == 0 {
+		return time.Duration(0)
+	}
+	return time.Duration(math.Pow(10, float64(attempts))) * time.Millisecond
+}
+
+func (c *syncCron) Schedule(s task.Schedule, t task.Command) error {
+	id := fmt.Sprintf("%s-%s", s.String(), t.String())
+
+	go func() {
+		// run the scheduler
+		tc := s.Run()
+
+		var i int
+
+		for {
+			// leader election
+			e, err := c.opts.Leader.Elect(id)
+			if err != nil {
+				log.Logf("[cron] leader election error: %v", err)
+				time.Sleep(backoff(i))
+				i++
+				continue
+			}
+
+			i = 0
+			r := e.Revoked()
+
+			// execute the task
+		Tick:
+			for {
+				select {
+				// schedule tick
+				case _, ok := <-tc:
+					// ticked once
+					if !ok {
+						break Tick
+					}
+
+					log.Logf("[cron] executing command %s", t.Name)
+					if err := c.opts.Task.Run(t); err != nil {
+						log.Logf("[cron] error executing command %s: %v", t.Name, err)
+					}
+				// leader revoked
+				case <-r:
+					break Tick
+				}
+			}
+
+			// resign
+			e.Resign()
+		}
+	}()
+
+	return nil
+}
+
+func NewCron(opts ...Option) Cron {
+	var options Options
+	for _, o := range opts {
+		o(&options)
+	}
+
+	if options.Leader == nil {
+		options.Leader = consul.NewLeader()
+	}
+
+	if options.Task == nil {
+		options.Task = local.NewTask()
+	}
+
+	return &syncCron{
+		opts: options,
+	}
+}