// tick attempts to schedule the queue.
func (s *Scheduler) tick(ctx context.Context) {
tasksByCommonSpec := make(map[string]map[string]*api.Task)
schedulingDecisions := make(map[string]schedulingDecision, s.unassignedTasks.Len())
var next *list.Element
for e := s.unassignedTasks.Front(); e != nil; e = next {
next = e.Next()
t := s.allTasks[e.Value.(*api.Task).ID]
if t == nil || t.NodeID != "" {
// task deleted or already assigned
s.unassignedTasks.Remove(e)
continue
}
// Group common tasks with common specs by marshalling the spec
// into taskKey and using it as a map key.
// TODO(aaronl): Once specs are versioned, this will allow a
// much more efficient fast path.
fieldsToMarshal := api.Task{
ServiceID: t.ServiceID,
Spec: t.Spec,
}
marshalled, err := fieldsToMarshal.Marshal()
if err != nil {
panic(err)
}
taskGroupKey := string(marshalled)
if tasksByCommonSpec[taskGroupKey] == nil {
tasksByCommonSpec[taskGroupKey] = make(map[string]*api.Task)
}
tasksByCommonSpec[taskGroupKey][t.ID] = t
s.unassignedTasks.Remove(e)
}
for _, taskGroup := range tasksByCommonSpec {
s.scheduleTaskGroup(ctx, taskGroup, schedulingDecisions)
}
_, failed := s.applySchedulingDecisions(ctx, schedulingDecisions)
for _, decision := range failed {
s.allTasks[decision.old.ID] = decision.old
nodeInfo, err := s.nodeSet.nodeInfo(decision.new.NodeID)
if err == nil && nodeInfo.removeTask(decision.new) {
s.nodeSet.updateNode(nodeInfo)
}
// enqueue task for next scheduling attempt
s.enqueue(decision.old)
}
}
