fix(jobs): run periodic jobs once at start time (#89)

a recent refactor of `DoPeriodic` (inadvertently) removed the initial invocation of a periodic job, and waited instead until the first frequency interval to execute. We want the first execution to be immediate.

Includes updates to tests that verify expected job execution counts after definite time lapse periods.

Author: jackfrancis

jobs/jobs.go

@@ -102,12 +102,18 @@ func (u getLatestVersionData) Frequency() time.Duration {
 	return u.frequency
 }
 
-// DoPeriodic calls p.Do() every p.Frequency() on each element p in pSlice. For each p in pSlice,
-// a new goroutine is started, and the returned channel can be closed to stop all of the goroutines
+// DoPeriodic calls p.Do() once, and then again every p.Frequency() on each element p in pSlice.
+// For each p in pSlice, a new goroutine is started, and the returned channel can be closed
+// to stop all of the goroutines.
 func DoPeriodic(pSlice []Periodic) chan<- struct{} {
 	doneCh := make(chan struct{})
 	for _, p := range pSlice {
 		go func(p Periodic) {
+			// execute once at the beginning
+			err := p.Do()
+			if err != nil {
+				log.Printf("periodic job ran and returned error (%s)", err)
+			}
 			ticker := time.NewTicker(p.Frequency())
 			for {
 				select {

jobs/jobs_test.go

@@ -25,10 +25,14 @@ func (t testPeriodic) Frequency() time.Duration {
 }
 
 func TestDoPeriodic(t *testing.T) {
-	interval := time.Duration(100) * time.Millisecond
+	interval := time.Duration(3000) * time.Millisecond
 	p := &testPeriodic{t: t, err: nil, freq: interval}
 	closeCh1 := DoPeriodic([]Periodic{p})
-	time.Sleep(interval * 2)
-	assert.True(t, p.i >= 1, "the periodic wasn't called at least once")
+	time.Sleep(interval / 2) // wait a little while for the goroutine to call the job once
+	assert.True(t, p.i == 1, "the periodic wasn't called once")
+	time.Sleep(interval)
+	assert.True(t, p.i == 2, "the periodic wasn't called twice")
+	time.Sleep(interval)
+	assert.True(t, p.i == 3, "the periodic wasn't called thrice")
 	close(closeCh1)
 }