Add cron schedules and sync docs

agent/internal/scheduler/scheduler_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/monlet/agent/internal/config"
+	"github.com/robfig/cron/v3"
 )
 
 func runScheduler(ctx context.Context, agentID string, checks []config.CheckConfig, out chan<- Event, h Hooks) {
@@ -27,6 +28,32 @@ func mkCheck(id, cmd string, interval, timeout time.Duration) config.CheckConfig
 	}
 }
 
+type fakeCronSchedule struct {
+	delay time.Duration
+}
+
+func (s fakeCronSchedule) Next(t time.Time) time.Time {
+	return t.Add(s.delay)
+}
+
+func withFakeCron(t *testing.T, delay time.Duration) {
+	t.Helper()
+	old := parseCronSchedule
+	parseCronSchedule = func(string) (cron.Schedule, error) {
+		return fakeCronSchedule{delay: delay}, nil
+	}
+	t.Cleanup(func() { parseCronSchedule = old })
+}
+
+func mkCronCheck(id, cmd string, timeout time.Duration) config.CheckConfig {
+	return config.CheckConfig{
+		ID:      id,
+		Command: cmd,
+		Cron:    "0 * * * *",
+		Timeout: config.Duration{Duration: timeout},
+	}
+}
+
 func TestEmitsEvents(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
 	defer cancel()
@@ -45,6 +72,41 @@ func TestEmitsEvents(t *testing.T) {
 	}
 }
 
+func TestCronDoesNotRunImmediately(t *testing.T) {
+	withFakeCron(t, 200*time.Millisecond)
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+	out := make(chan Event, 10)
+	m := NewManager(ctx, "a1", out, Hooks{})
+	m.Update([]config.CheckConfig{mkCronCheck("cron", "echo cron", 100*time.Millisecond)})
+	select {
+	case ev := <-out:
+		t.Fatalf("cron check ran before next slot: %+v", ev)
+	case <-ctx.Done():
+	}
+	m.Stop()
+	m.Wait()
+}
+
+func TestCronEmitsOnDueSlot(t *testing.T) {
+	withFakeCron(t, 30*time.Millisecond)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	out := make(chan Event, 10)
+	m := NewManager(ctx, "a1", out, Hooks{})
+	m.Update([]config.CheckConfig{mkCronCheck("cron", "echo cron", 100*time.Millisecond)})
+	select {
+	case ev := <-out:
+		if ev.CheckID != "cron" || ev.Status != "ok" {
+			t.Fatalf("unexpected event: %+v", ev)
+		}
+	case <-ctx.Done():
+		t.Fatal("no cron event")
+	}
+	m.Stop()
+	m.Wait()
+}
+
 func TestNoOverlapSkips(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), 600*time.Millisecond)
 	defer cancel()
@@ -59,6 +121,23 @@ func TestNoOverlapSkips(t *testing.T) {
 	}
 }
 
+func TestCronNoOverlapSkips(t *testing.T) {
+	withFakeCron(t, 50*time.Millisecond)
+	ctx, cancel := context.WithTimeout(context.Background(), 250*time.Millisecond)
+	defer cancel()
+	out := make(chan Event, 10)
+	var skipped int32
+	hooks := Hooks{OnSkipped: func(string) { atomic.AddInt32(&skipped, 1) }}
+	m := NewManager(ctx, "a1", out, hooks)
+	m.Update([]config.CheckConfig{mkCronCheck("cron", "sleep 0.2", 500*time.Millisecond)})
+	<-ctx.Done()
+	m.Stop()
+	m.Wait()
+	if atomic.LoadInt32(&skipped) == 0 {
+		t.Fatal("expected at least one skipped cron slot")
+	}
+}
+
 func TestReportsFullEventChannel(t *testing.T) {
 	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
 	defer cancel()