add new features, OneTimeJob and Job.RunNow() (#646)

README.md

@@ -87,6 +87,8 @@ Jobs can be run every x days at specific times.
 Jobs can be run every x weeks on specific days of the week and at specific times.
 - [**Monthly**](https://pkg.go.dev/github.com/go-co-op/gocron/v2#MonthlyJob):
 Jobs can be run every x months on specific days of the month and at specific times.
+- [**One time**](https://pkg.go.dev/github.com/go-co-op/gocron/v2#OneTimeJob):
+Jobs can be run once at a specific time. These are non-recurring jobs.
 
 ### Concurrency Limits
 Jobs can be limited individually or across the entire scheduler.

errors.go

@@ -12,6 +12,7 @@ var (
 	ErrDurationRandomJobMinMax       = fmt.Errorf("gocron: DurationRandomJob: minimum duration must be less than maximum duration")
 	ErrEventListenerFuncNil          = fmt.Errorf("gocron: eventListenerFunc must not be nil")
 	ErrJobNotFound                   = fmt.Errorf("gocron: job not found")
+	ErrJobRunNowFailed               = fmt.Errorf("gocron: Job: RunNow: scheduler unreachable")
 	ErrMonthlyJobDays                = fmt.Errorf("gocron: MonthlyJob: daysOfTheMonth must be between 31 and -31 inclusive, and not 0")
 	ErrMonthlyJobAtTimeNil           = fmt.Errorf("gocron: MonthlyJob: atTime within atTimes must not be nil")
 	ErrMonthlyJobAtTimesNil          = fmt.Errorf("gocron: MonthlyJob: atTimes must not be nil")
@@ -22,6 +23,7 @@ var (
 	ErrNewJobTaskNotFunc             = fmt.Errorf("gocron: NewJob: Task.Function must be of kind reflect.Func")
 	ErrNewJobWrongNumberOfParameters = fmt.Errorf("gocron: NewJob: Number of provided parameters does not match expected")
 	ErrNewJobWrongTypeOfParameters   = fmt.Errorf("gocron: NewJob: Type of provided parameters does not match expected")
+	ErrOneTimeJobStartDateTimePast   = fmt.Errorf("gocron: OneTimeJob: start must not be in the past")
 	ErrStopExecutorTimedOut          = fmt.Errorf("gocron: timed out waiting for executor to stop")
 	ErrStopJobsTimedOut              = fmt.Errorf("gocron: timed out waiting for jobs to finish")
 	ErrStopSchedulerTimedOut         = fmt.Errorf("gocron: timed out waiting for scheduler to stop")

example_test.go

@@ -196,6 +196,28 @@ func ExampleJob_NextRun() {
 	fmt.Println(j.NextRun())
 }
 
+func ExampleJob_RunNow() {
+	s, _ := NewScheduler()
+	defer func() { _ = s.Shutdown() }()
+
+	j, _ := s.NewJob(
+		MonthlyJob(
+			1,
+			NewDaysOfTheMonth(3, -5, -1),
+			NewAtTimes(
+				NewAtTime(10, 30, 0),
+				NewAtTime(11, 15, 0),
+			),
+		),
+		NewTask(
+			func() {},
+		),
+	)
+	s.Start()
+	// Runs the job one time now, without impacting the schedule
+	_ = j.RunNow()
+}
+
 func ExampleMonthlyJob() {
 	s, _ := NewScheduler()
 	defer func() { _ = s.Shutdown() }()
@@ -222,6 +244,32 @@ func ExampleNewScheduler() {
 	fmt.Println(s.Jobs())
 }
 
+func ExampleOneTimeJob() {
+	s, _ := NewScheduler()
+	defer func() { _ = s.Shutdown() }()
+
+	// run a job once, immediately
+	_, _ = s.NewJob(
+		OneTimeJob(
+			OneTimeJobStartImmediately(),
+		),
+		NewTask(
+			func() {},
+		),
+	)
+	// run a job once in 10 seconds
+	_, _ = s.NewJob(
+		OneTimeJob(
+			OneTimeJobStartDateTime(time.Now().Add(10*time.Second)),
+		),
+		NewTask(
+			func() {},
+		),
+	)
+
+	s.Start()
+}
+
 func ExampleScheduler_NewJob() {
 	s, _ := NewScheduler()
 	defer func() { _ = s.Shutdown() }()

executor.go

@@ -14,7 +14,7 @@ type executor struct {
 	cancel           context.CancelFunc
 	logger           Logger
 	stopCh           chan struct{}
-	jobsIDsIn        chan uuid.UUID
+	jobsIn           chan jobIn
 	jobIDsOut        chan uuid.UUID
 	jobOutRequest    chan jobOutRequest
 	stopTimeout      time.Duration
@@ -25,8 +25,13 @@ type executor struct {
 	locker           Locker
 }
 
+type jobIn struct {
+	id            uuid.UUID
+	shouldSendOut bool
+}
+
 type singletonRunner struct {
-	in                chan uuid.UUID
+	in                chan jobIn
 	rescheduleLimiter chan struct{}
 }
 
@@ -35,7 +40,7 @@ type limitModeConfig struct {
 	mode              LimitMode
 	limit             uint
 	rescheduleLimiter chan struct{}
-	in                chan uuid.UUID
+	in                chan jobIn
 	// singletonJobs is used to track singleton jobs that are running
 	// in the limit mode runner. This is used to prevent the same job
 	// from running multiple times across limit mode runners when both
@@ -72,7 +77,7 @@ func (e *executor) start() {
 		//    are run immediately.
 		// 2. sent from time.AfterFuncs in which job schedules
 		// 	  are spun up by the scheduler
-		case id := <-e.jobsIDsIn:
+		case jIn := <-e.jobsIn:
 			select {
 			case <-e.stopCh:
 				e.stop(standardJobsWg, singletonJobsWg, limitModeJobsWg)
@@ -111,23 +116,25 @@ func (e *executor) start() {
 						// the executor from building up a waiting queue
 						// and forces rescheduling
 						case e.limitMode.rescheduleLimiter <- struct{}{}:
-							e.limitMode.in <- id
+							e.limitMode.in <- jIn
 						default:
 							// all runners are busy, reschedule the work for later
 							// which means we just skip it here and do nothing
 							// TODO when metrics are added, this should increment a rescheduled metric
+							if jIn.shouldSendOut {
 								select {
-							case e.jobIDsOut <- id:
+								case e.jobIDsOut <- jIn.id:
 								default:
 								}
 							}
+						}
 					} else {
 						// since we're not using LimitModeReschedule, but instead using LimitModeWait
 						// we do want to queue up the work to the limit mode runners and allow them
 						// to work through the channel backlog. A hard limit of 1000 is in place
 						// at which point this call would block.
 						// TODO when metrics are added, this should increment a wait metric
-						e.limitMode.in <- id
+						e.limitMode.in <- jIn
 					}
 				} else {
 					// no limit mode, so we're either running a regular job or
@@ -135,7 +142,7 @@ func (e *executor) start() {
 					//
 					// get the job, so we can figure out what kind it is and how
 					// to execute it
-					j := requestJobCtx(ctx, id, e.jobOutRequest)
+					j := requestJobCtx(ctx, jIn.id, e.jobOutRequest)
 					if j == nil {
 						// safety check as it'd be strange bug if this occurred
 						return
@@ -143,15 +150,15 @@ func (e *executor) start() {
 					if j.singletonMode {
 						// for singleton mode, get the existing runner for the job
 						// or spin up a new one
-						runner, ok := e.singletonRunners[id]
+						runner, ok := e.singletonRunners[jIn.id]
 						if !ok {
-							runner.in = make(chan uuid.UUID, 1000)
+							runner.in = make(chan jobIn, 1000)
 							if j.singletonLimitMode == LimitModeReschedule {
 								runner.rescheduleLimiter = make(chan struct{}, 1)
 							}
-							e.singletonRunners[id] = runner
+							e.singletonRunners[jIn.id] = runner
 							singletonJobsWg.Add(1)
-							go e.singletonModeRunner("singleton-"+id.String(), runner.in, singletonJobsWg, j.singletonLimitMode, runner.rescheduleLimiter)
+							go e.singletonModeRunner("singleton-"+jIn.id.String(), runner.in, singletonJobsWg, j.singletonLimitMode, runner.rescheduleLimiter)
 						}
 
 						if j.singletonLimitMode == LimitModeReschedule {
@@ -159,19 +166,21 @@ func (e *executor) start() {
 							// for a running job and reschedules if the channel is full.
 							select {
 							case runner.rescheduleLimiter <- struct{}{}:
-								runner.in <- id
+								runner.in <- jIn
 							default:
 								// runner is busy, reschedule the work for later
 								// which means we just skip it here and do nothing
 								// TODO when metrics are added, this should increment a rescheduled metric
+								if jIn.shouldSendOut {
 									select {
-								case e.jobIDsOut <- id:
+									case e.jobIDsOut <- jIn.id:
 									default:
 									}
 								}
+							}
 						} else {
 							// wait mode, fill up that queue (buffered channel, so it's ok)
-							runner.in <- id
+							runner.in <- jIn
 						}
 					} else {
 						select {
@@ -187,7 +196,7 @@ func (e *executor) start() {
 						// complete.
 						standardJobsWg.Add(1)
 						go func(j internalJob) {
-							e.runJob(j)
+							e.runJob(j, jIn.shouldSendOut)
 							standardJobsWg.Done()
 						}(*j)
 					}
@@ -200,11 +209,11 @@ func (e *executor) start() {
 	}
 }
 
-func (e *executor) limitModeRunner(name string, in chan uuid.UUID, wg *waitGroupWithMutex, limitMode LimitMode, rescheduleLimiter chan struct{}) {
+func (e *executor) limitModeRunner(name string, in chan jobIn, wg *waitGroupWithMutex, limitMode LimitMode, rescheduleLimiter chan struct{}) {
 	e.logger.Debug("gocron: limitModeRunner starting", "name", name)
 	for {
 		select {
-		case id := <-in:
+		case jIn := <-in:
 			select {
 			case <-e.ctx.Done():
 				e.logger.Debug("gocron: limitModeRunner shutting down", "name", name)
@@ -214,16 +223,17 @@ func (e *executor) limitModeRunner(name string, in chan uuid.UUID, wg *waitGroup
 			}
 
 			ctx, cancel := context.WithCancel(e.ctx)
-			j := requestJobCtx(ctx, id, e.jobOutRequest)
+			j := requestJobCtx(ctx, jIn.id, e.jobOutRequest)
 			cancel()
 			if j != nil {
 				if j.singletonMode {
 					e.limitMode.singletonJobsMu.Lock()
-					_, ok := e.limitMode.singletonJobs[id]
+					_, ok := e.limitMode.singletonJobs[jIn.id]
 					if ok {
 						// this job is already running, so don't run it
 						// but instead reschedule it
 						e.limitMode.singletonJobsMu.Unlock()
+						if jIn.shouldSendOut {
 							select {
 							case <-e.ctx.Done():
 								return
@@ -231,7 +241,10 @@ func (e *executor) limitModeRunner(name string, in chan uuid.UUID, wg *waitGroup
 								return
 							case e.jobIDsOut <- j.id:
 							}
-						// remove the limiter block to allow another job to be scheduled
+						}
+						// remove the limiter block, as this particular job
+						// was a singleton already running, and we want to
+						// allow another job to be scheduled
 						if limitMode == LimitModeReschedule {
 							select {
 							case <-rescheduleLimiter:
@@ -240,14 +253,14 @@ func (e *executor) limitModeRunner(name string, in chan uuid.UUID, wg *waitGroup
 						}
 						continue
 					}
-					e.limitMode.singletonJobs[id] = struct{}{}
+					e.limitMode.singletonJobs[jIn.id] = struct{}{}
 					e.limitMode.singletonJobsMu.Unlock()
 				}
-				e.runJob(*j)
+				e.runJob(*j, jIn.shouldSendOut)
 
 				if j.singletonMode {
 					e.limitMode.singletonJobsMu.Lock()
-					delete(e.limitMode.singletonJobs, id)
+					delete(e.limitMode.singletonJobs, jIn.id)
 					e.limitMode.singletonJobsMu.Unlock()
 				}
 			}
@@ -267,24 +280,24 @@ func (e *executor) limitModeRunner(name string, in chan uuid.UUID, wg *waitGroup
 	}
 }
 
-func (e *executor) singletonModeRunner(name string, in chan uuid.UUID, wg *waitGroupWithMutex, limitMode LimitMode, rescheduleLimiter chan struct{}) {
+func (e *executor) singletonModeRunner(name string, in chan jobIn, wg *waitGroupWithMutex, limitMode LimitMode, rescheduleLimiter chan struct{}) {
-	e.logger.Debug("gocron: limitModeRunner starting", "name", name)
+	e.logger.Debug("gocron: singletonModeRunner starting", "name", name)
 	for {
 		select {
-		case id := <-in:
+		case jIn := <-in:
 			select {
 			case <-e.ctx.Done():
-				e.logger.Debug("gocron: limitModeRunner shutting down", "name", name)
+				e.logger.Debug("gocron: singletonModeRunner shutting down", "name", name)
 				wg.Done()
 				return
 			default:
 			}
 
 			ctx, cancel := context.WithCancel(e.ctx)
-			j := requestJobCtx(ctx, id, e.jobOutRequest)
+			j := requestJobCtx(ctx, jIn.id, e.jobOutRequest)
 			cancel()
 			if j != nil {
-				e.runJob(*j)
+				e.runJob(*j, jIn.shouldSendOut)
 			}
 
 			// remove the limiter block to allow another job to be scheduled
@@ -295,14 +308,14 @@ func (e *executor) singletonModeRunner(name string, in chan uuid.UUID, wg *waitG
 				}
 			}
 		case <-e.ctx.Done():
-			e.logger.Debug("limitModeRunner shutting down", "name", name)
+			e.logger.Debug("singletonModeRunner shutting down", "name", name)
 			wg.Done()
 			return
 		}
 	}
 }
 
-func (e *executor) runJob(j internalJob) {
+func (e *executor) runJob(j internalJob, shouldSendOut bool) {
 	if j.ctx == nil {
 		return
 	}
@@ -327,6 +340,7 @@ func (e *executor) runJob(j internalJob) {
 	}
 	_ = callJobFuncWithParams(j.beforeJobRuns, j.id, j.name)
 
+	if shouldSendOut {
 		select {
 		case <-e.ctx.Done():
 			return
@@ -334,6 +348,7 @@ func (e *executor) runJob(j internalJob) {
 			return
 		case e.jobIDsOut <- j.id:
 		}
+	}
 
 	err := callJobFuncWithParams(j.function, j.parameters...)
 	if err != nil {

job.go

@@ -426,6 +426,48 @@ func MonthlyJob(interval uint, daysOfTheMonth DaysOfTheMonth, atTimes AtTimes) J
 	}
 }
 
+var _ JobDefinition = (*oneTimeJobDefinition)(nil)
+
+type oneTimeJobDefinition struct {
+	startAt OneTimeJobStartAtOption
+}
+
+func (o oneTimeJobDefinition) setup(j *internalJob, _ *time.Location) error {
+	j.jobSchedule = oneTimeJob{}
+	return o.startAt(j)
+}
+
+// OneTimeJobStartAtOption defines when the one time job is run
+type OneTimeJobStartAtOption func(*internalJob) error
+
+// OneTimeJobStartImmediately tells the scheduler to run the one time job immediately.
+func OneTimeJobStartImmediately() OneTimeJobStartAtOption {
+	return func(j *internalJob) error {
+		j.startImmediately = true
+		return nil
+	}
+}
+
+// OneTimeJobStartDateTime sets the date & time at which the job should run.
+// This datetime must be in the future.
+func OneTimeJobStartDateTime(start time.Time) OneTimeJobStartAtOption {
+	return func(j *internalJob) error {
+		if start.IsZero() || start.Before(time.Now()) {
+			return ErrOneTimeJobStartDateTimePast
+		}
+		j.startTime = start
+		return nil
+	}
+}
+
+// OneTimeJob is to run a job once at a specified time and not on
+// any regular schedule.
+func OneTimeJob(startAt OneTimeJobStartAtOption) JobDefinition {
+	return oneTimeJobDefinition{
+		startAt: startAt,
+	}
+}
+
 // -----------------------------------------------
 // -----------------------------------------------
 // ----------------- Job Options -----------------
@@ -772,6 +814,14 @@ func (m monthlyJob) nextMonthDayAtTime(lastRun time.Time, days []int, firstPass
 	return time.Time{}
 }
 
+var _ jobSchedule = (*oneTimeJob)(nil)
+
+type oneTimeJob struct{}
+
+func (o oneTimeJob) next(_ time.Time) time.Time {
+	return time.Time{}
+}
+
 // -----------------------------------------------
 // -----------------------------------------------
 // ---------------- Job Interface ----------------
@@ -786,6 +836,7 @@ type Job interface {
 	Name() string
 	NextRun() (time.Time, error)
 	Tags() []string
+	RunNow() error
 }
 
 var _ Job = (*job)(nil)
@@ -799,6 +850,7 @@ type job struct {
 	name          string
 	tags          []string
 	jobOutRequest chan jobOutRequest
+	runJobRequest chan runJobRequest
 }
 
 // ID returns the job's unique identifier.
@@ -833,3 +885,29 @@ func (j job) NextRun() (time.Time, error) {
 func (j job) Tags() []string {
 	return j.tags
 }
+
+// RunNow runs the job once, now. This does not alter
+// the existing run schedule, and will respect all job
+// and scheduler limits.
+func (j job) RunNow() error {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	resp := make(chan error, 1)
+
+	select {
+	case j.runJobRequest <- runJobRequest{
+		id:      j.id,
+		outChan: resp,
+	}:
+	case <-time.After(100 * time.Millisecond):
+		return ErrJobRunNowFailed
+	}
+	var err error
+	select {
+	case <-ctx.Done():
+		return ErrJobRunNowFailed
+	case errReceived := <-resp:
+		err = errReceived
+	}
+	return err
+}

job_test.go

@@ -319,6 +319,25 @@ func TestDurationRandomJob_next(t *testing.T) {
 	}
 }
 
+func TestOneTimeJob_next(t *testing.T) {
+	otj := oneTimeJob{}
+	assert.Zero(t, otj.next(time.Time{}))
+}
+
+func TestJob_RunNow_Error(t *testing.T) {
+	s := newTestScheduler(t)
+
+	j, err := s.NewJob(
+		DurationJob(time.Second),
+		NewTask(func() {}),
+	)
+	require.NoError(t, err)
+
+	require.NoError(t, s.Shutdown())
+
+	assert.EqualError(t, j.RunNow(), ErrJobRunNowFailed.Error())
+}
+
 func TestJob_LastRun(t *testing.T) {
 	testTime := time.Date(2000, 1, 1, 0, 0, 0, 0, time.Local)
 	fakeClock := clockwork.NewFakeClockAt(testTime)

scheduler.go

@@ -49,6 +49,7 @@ type scheduler struct {
 	stopErrCh          chan error
 	allJobsOutRequest  chan allJobsOutRequest
 	jobOutRequestCh    chan jobOutRequest
+	runJobRequestCh    chan runJobRequest
 	newJobCh           chan internalJob
 	removeJobCh        chan uuid.UUID
 	removeJobsByTagsCh chan []string
@@ -59,6 +60,11 @@ type jobOutRequest struct {
 	outChan chan internalJob
 }
 
+type runJobRequest struct {
+	id      uuid.UUID
+	outChan chan error
+}
+
 type allJobsOutRequest struct {
 	outChan chan []Job
 }
@@ -77,7 +83,7 @@ func NewScheduler(options ...SchedulerOption) (Scheduler, error) {
 		singletonRunners: make(map[uuid.UUID]singletonRunner),
 		logger:           &noOpLogger{},
 
-		jobsIDsIn:     make(chan uuid.UUID),
+		jobsIn:        make(chan jobIn),
 		jobIDsOut:     make(chan uuid.UUID),
 		jobOutRequest: make(chan jobOutRequest, 1000),
 		done:          make(chan error),
@@ -100,6 +106,7 @@ func NewScheduler(options ...SchedulerOption) (Scheduler, error) {
 		stopCh:             make(chan struct{}),
 		stopErrCh:          make(chan error, 1),
 		jobOutRequestCh:    make(chan jobOutRequest),
+		runJobRequestCh:    make(chan runJobRequest),
 		allJobsOutRequest:  make(chan allJobsOutRequest),
 	}
 
@@ -135,6 +142,9 @@ func NewScheduler(options ...SchedulerOption) (Scheduler, error) {
 			case out := <-s.allJobsOutRequest:
 				s.selectAllJobsOutRequest(out)
 
+			case run := <-s.runJobRequestCh:
+				s.selectRunJobRequest(run)
+
 			case <-s.startCh:
 				s.selectStart()
 
@@ -204,6 +214,31 @@ func (s *scheduler) selectAllJobsOutRequest(out allJobsOutRequest) {
 	}
 }
 
+func (s *scheduler) selectRunJobRequest(run runJobRequest) {
+	j, ok := s.jobs[run.id]
+	if !ok {
+		select {
+		case run.outChan <- ErrJobNotFound:
+		default:
+		}
+	}
+	select {
+	case <-s.shutdownCtx.Done():
+		select {
+		case run.outChan <- ErrJobRunNowFailed:
+		default:
+		}
+	case s.exec.jobsIn <- jobIn{
+		id:            j.id,
+		shouldSendOut: false,
+	}:
+		select {
+		case run.outChan <- nil:
+		default:
+		}
+	}
+}
+
 func (s *scheduler) selectRemoveJob(id uuid.UUID) {
 	j, ok := s.jobs[id]
 	if !ok {
@@ -232,12 +267,18 @@ func (s *scheduler) selectExecJobIDsOut(id uuid.UUID) {
 	}
 
 	next := j.next(j.lastRun)
+	if next.IsZero() {
+		return
+	}
 	j.nextRun = next
 	j.timer = s.clock.AfterFunc(next.Sub(s.now()), func() {
 		select {
 		case <-s.shutdownCtx.Done():
 			return
-		case s.exec.jobsIDsIn <- id:
+		case s.exec.jobsIn <- jobIn{
+			id:            j.id,
+			shouldSendOut: true,
+		}:
 		}
 	})
 	s.jobs[id] = j
@@ -260,7 +301,10 @@ func (s *scheduler) selectNewJob(j internalJob) {
 			next = s.now()
 			select {
 			case <-s.shutdownCtx.Done():
-			case s.exec.jobsIDsIn <- j.id:
+			case s.exec.jobsIn <- jobIn{
+				id:            j.id,
+				shouldSendOut: true,
+			}:
 			}
 		} else {
 			if next.IsZero() {
@@ -271,7 +315,10 @@ func (s *scheduler) selectNewJob(j internalJob) {
 			j.timer = s.clock.AfterFunc(next.Sub(s.now()), func() {
 				select {
 				case <-s.shutdownCtx.Done():
-				case s.exec.jobsIDsIn <- id:
+				case s.exec.jobsIn <- jobIn{
+					id:            id,
+					shouldSendOut: true,
+				}:
 				}
 			})
 		}
@@ -304,7 +351,10 @@ func (s *scheduler) selectStart() {
 			next = s.now()
 			select {
 			case <-s.shutdownCtx.Done():
-			case s.exec.jobsIDsIn <- id:
+			case s.exec.jobsIn <- jobIn{
+				id:            id,
+				shouldSendOut: true,
+			}:
 			}
 		} else {
 			if next.IsZero() {
@@ -315,7 +365,10 @@ func (s *scheduler) selectStart() {
 			j.timer = s.clock.AfterFunc(next.Sub(s.now()), func() {
 				select {
 				case <-s.shutdownCtx.Done():
-				case s.exec.jobsIDsIn <- jobID:
+				case s.exec.jobsIn <- jobIn{
+					id:            jobID,
+					shouldSendOut: true,
+				}:
 				}
 			})
 		}
@@ -453,6 +506,7 @@ func (s *scheduler) addOrUpdateJob(id uuid.UUID, definition JobDefinition, taskW
 		name:          j.name,
 		tags:          slices.Clone(j.tags),
 		jobOutRequest: s.jobOutRequestCh,
+		runJobRequest: s.runJobRequestCh,
 	}, nil
 }
 
@@ -632,7 +686,7 @@ func WithLimitConcurrentJobs(limit uint, mode LimitMode) SchedulerOption {
 		s.exec.limitMode = &limitModeConfig{
 			mode:          mode,
 			limit:         limit,
-			in:            make(chan uuid.UUID, 1000),
+			in:            make(chan jobIn, 1000),
 			singletonJobs: make(map[uuid.UUID]struct{}),
 		}
 		if mode == LimitModeReschedule {

scheduler_test.go

@@ -719,6 +719,18 @@ func TestScheduler_NewJobErrors(t *testing.T) {
 			[]JobOption{WithStartAt(WithStartDateTime(time.Now().Add(-time.Second)))},
 			ErrWithStartDateTimePast,
 		},
+		{
+			"oneTimeJob start at is zero",
+			OneTimeJob(OneTimeJobStartDateTime(time.Time{})),
+			nil,
+			ErrOneTimeJobStartDateTimePast,
+		},
+		{
+			"oneTimeJob start at is in past",
+			OneTimeJob(OneTimeJobStartDateTime(time.Now().Add(-time.Second))),
+			nil,
+			ErrOneTimeJobStartDateTimePast,
+		},
 	}
 
 	for _, tt := range tests {
@@ -1425,3 +1437,201 @@ func TestScheduler_ManyJobs(t *testing.T) {
 	assert.GreaterOrEqual(t, count, 9900)
 	assert.LessOrEqual(t, count, 11000)
 }
+
+func TestScheduler_RunJobNow(t *testing.T) {
+	chDuration := make(chan struct{}, 10)
+	chMonthly := make(chan struct{}, 10)
+	chDurationImmediate := make(chan struct{}, 10)
+	chDurationSingleton := make(chan struct{}, 10)
+	chOneTime := make(chan struct{}, 10)
+
+	tests := []struct {
+		name         string
+		ch           chan struct{}
+		j            JobDefinition
+		fun          any
+		opts         []JobOption
+		expectedDiff func() time.Duration
+		expectedRuns int
+	}{
+		{
+			"duration job",
+			chDuration,
+			DurationJob(time.Second * 10),
+			func() {
+				chDuration <- struct{}{}
+			},
+			nil,
+			func() time.Duration {
+				return 0
+			},
+			1,
+		},
+		{
+			"monthly job",
+			chMonthly,
+			MonthlyJob(1, NewDaysOfTheMonth(1), NewAtTimes(NewAtTime(0, 0, 0))),
+			func() {
+				chMonthly <- struct{}{}
+			},
+			nil,
+			func() time.Duration {
+				return 0
+			},
+			1,
+		},
+		{
+			"duration job - start immediately",
+			chDurationImmediate,
+			DurationJob(time.Second * 10),
+			func() {
+				chDurationImmediate <- struct{}{}
+			},
+			[]JobOption{
+				WithStartAt(
+					WithStartImmediately(),
+				),
+			},
+			func() time.Duration {
+				return 10 * time.Second
+			},
+			2,
+		},
+		{
+			"duration job - singleton",
+			chDurationSingleton,
+			DurationJob(time.Second * 10),
+			func() {
+				chDurationSingleton <- struct{}{}
+				time.Sleep(200 * time.Millisecond)
+			},
+			[]JobOption{
+				WithStartAt(
+					WithStartImmediately(),
+				),
+				WithSingletonMode(LimitModeReschedule),
+			},
+			func() time.Duration {
+				return 10 * time.Second
+			},
+			1,
+		},
+		{
+			"one time job",
+			chOneTime,
+			OneTimeJob(OneTimeJobStartImmediately()),
+			func() {
+				chOneTime <- struct{}{}
+			},
+			nil,
+			nil,
+			2,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := newTestScheduler(t)
+
+			j, err := s.NewJob(tt.j, NewTask(tt.fun), tt.opts...)
+			require.NoError(t, err)
+
+			s.Start()
+
+			var nextRunBefore time.Time
+			if tt.expectedDiff != nil {
+				for ; nextRunBefore.IsZero() || err != nil; nextRunBefore, err = j.NextRun() { //nolint:revive
+				}
+			}
+
+			assert.NoError(t, err)
+
+			time.Sleep(100 * time.Millisecond)
+			require.NoError(t, j.RunNow())
+			var runCount int
+
+			select {
+			case <-tt.ch:
+				runCount++
+			case <-time.After(time.Second):
+				t.Fatal("timed out waiting for job to run")
+			}
+
+			timeout := time.Now().Add(time.Second)
+			for time.Now().Before(timeout) {
+				select {
+				case <-tt.ch:
+					runCount++
+				default:
+				}
+			}
+
+			assert.Equal(t, tt.expectedRuns, runCount)
+
+			nextRunAfter, err := j.NextRun()
+			if tt.expectedDiff != nil && tt.expectedDiff() > 0 {
+				for ; nextRunBefore.IsZero() || nextRunAfter.Equal(nextRunBefore); nextRunAfter, err = j.NextRun() { //nolint:revive
+				}
+			}
+
+			assert.NoError(t, err)
+			assert.NoError(t, s.Shutdown())
+
+			if tt.expectedDiff != nil {
+				assert.Equal(t, tt.expectedDiff(), nextRunAfter.Sub(nextRunBefore))
+			}
+		})
+	}
+}
+
+func TestScheduler_OneTimeJob(t *testing.T) {
+	tests := []struct {
+		name    string
+		startAt func() OneTimeJobStartAtOption
+	}{
+		{
+			"start now",
+			func() OneTimeJobStartAtOption {
+				return OneTimeJobStartImmediately()
+			},
+		},
+		{
+			"start in 100 ms",
+			func() OneTimeJobStartAtOption {
+				return OneTimeJobStartDateTime(time.Now().Add(100 * time.Millisecond))
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			jobRan := make(chan struct{}, 2)
+
+			s := newTestScheduler(t)
+
+			j, err := s.NewJob(
+				OneTimeJob(tt.startAt()),
+				NewTask(func() {
+					jobRan <- struct{}{}
+				}),
+			)
+			require.NoError(t, err)
+
+			s.Start()
+
+			select {
+			case <-jobRan:
+			case <-time.After(500 * time.Millisecond):
+				t.Fatal("timed out waiting for job to run")
+			}
+
+			var nextRun time.Time
+			for ; nextRun.IsZero(); nextRun, err = j.NextRun() { //nolint:revive
+			}
+			assert.NoError(t, err)
+			assert.True(t, nextRun.Before(time.Now()))
+
+			assert.NoError(t, s.Shutdown())
+		})
+	}
+}