WIP

task/scheduler.go

@@ -0,0 +1,147 @@
+package task
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/play-with-docker/play-with-docker/pwd/types"
+	"github.com/play-with-docker/play-with-docker/storage"
+)
+
+type Task interface {
+	Name() string
+	Run(ctx context.Context, instance *types.Instance) error
+}
+
+type SchedulerApi interface {
+	Schedule(session *types.Session) error
+	Unschedule(session *types.Session) error
+	Start()
+	Stop()
+	AddTask(task Task) error
+	RemoveTask(task Task) error
+}
+
+type scheduledSession struct {
+	session *types.Session
+	cancel  context.CancelFunc
+	ctx     context.Context
+	ticker  *time.Ticker
+}
+
+type scheduler struct {
+	scheduledSessions map[string]*scheduledSession
+	storage           storage.StorageApi
+	tasks             map[string]Task
+	started           bool
+}
+
+func NewScheduler(s storage.StorageApi) (*scheduler, error) {
+	sch := &scheduler{storage: s}
+
+	sch.tasks = make(map[string]Task)
+
+	err := sch.loadFromStorage()
+	if err != nil {
+		return nil, err
+	}
+
+	return sch, nil
+}
+
+func (s *scheduler) loadFromStorage() error {
+	sessions, err := s.storage.SessionGetAll()
+	if err != nil {
+		return err
+	}
+	s.scheduledSessions = make(map[string]*scheduledSession, len(sessions))
+	for _, session := range sessions {
+		s.register(session)
+	}
+
+	return nil
+}
+
+func (s *scheduler) AddTask(task Task) error {
+	if _, found := s.tasks[task.Name()]; found {
+		return fmt.Errorf("Task [%s] was already added", task.Name())
+	}
+	s.tasks[task.Name()] = task
+
+	return nil
+}
+
+func (s *scheduler) RemoveTask(task Task) error {
+	if _, found := s.tasks[task.Name()]; !found {
+		return fmt.Errorf("Task [%s] doesn't exist", task.Name())
+	}
+	delete(s.tasks, task.Name())
+
+	return nil
+}
+
+func (s *scheduler) Start() {
+	for _, session := range s.scheduledSessions {
+		go s.cron(session)
+	}
+	s.started = true
+}
+
+func (s *scheduler) register(session *types.Session) *scheduledSession {
+	ctx, cancel := context.WithCancel(context.Background())
+	s.scheduledSessions[session.Id] = &scheduledSession{session: session, cancel: cancel, ctx: ctx}
+	return s.scheduledSessions[session.Id]
+}
+
+func (s *scheduler) cron(session *scheduledSession) {
+	session.ticker = time.NewTicker(1 * time.Second)
+
+	for {
+		select {
+		case <-session.ticker.C:
+			s.processSession(session.ctx, session.session)
+		case <-session.ctx.Done():
+			return
+		}
+	}
+}
+
+func (s *scheduler) processSession(ctx context.Context, session *types.Session) {
+	for _, ins := range session.Instances {
+		go s.processInstance(ctx, ins)
+	}
+}
+
+func (s *scheduler) processInstance(ctx context.Context, instance *types.Instance) {
+	for _, task := range s.tasks {
+		task.Run(ctx, instance)
+	}
+}
+
+func (s *scheduler) Schedule(session *types.Session) error {
+	if !s.started {
+		return fmt.Errorf("Can only schedule sessions after the scheduler has been started.")
+	}
+	if _, found := s.scheduledSessions[session.Id]; found {
+		return fmt.Errorf("Session [%s] was already scheduled", session.Id)
+	}
+	go s.cron(s.register(session))
+	return nil
+}
+
+func (s *scheduler) Unschedule(session *types.Session) error {
+	if !s.started {
+		return fmt.Errorf("Can only schedule sessions after the scheduler has been started.")
+	}
+	if _, found := s.scheduledSessions[session.Id]; !found {
+		return fmt.Errorf("Session [%s] in not scheduled", session.Id)
+	}
+
+	scheduledSession := s.scheduledSessions[session.Id]
+	scheduledSession.cancel()
+	scheduledSession.ticker.Stop()
+	delete(s.scheduledSessions, session.Id)
+
+	return nil
+}