func gatherTasks(ds appwrap.Datastore, job JobInfo) ([]JobTask, error) {
taskKeys := makeTaskKeys(ds, job.FirstTaskId, job.TaskCount)
tasks := make([]JobTask, len(taskKeys))
i := 0
for i < len(taskKeys) {
last := i + 100
if last > len(taskKeys) {
last = len(taskKeys)
}
if err := ds.GetMulti(taskKeys[i:last], tasks[i:last]); err != nil {
return nil, err
}
i = last
}
return tasks, nil
}
// check if the specified job has completed. it should currently be at expectedStage, and if it's been completed
// we advance it to next stage. if it's already at nextStage another process has beaten us to it so we're done
//
// caller needs to check the stage in the final job; if stageChanged is true it will be either nextStage or StageFailed.
// If StageFailed then at least one of the underlying tasks failed and the reason will appear as a taskError{} in err
func jobStageComplete(c context.Context, ds appwrap.Datastore, jobKey *datastore.Key, taskKeys []*datastore.Key, expectedStage, nextStage JobStage) (stageChanged bool, job JobInfo, finalErr error) {
last := len(taskKeys)
tasks := make([]JobTask, 100)
for last > 0 {
first := last - 100
if first < 0 {
first = 0
}
taskCount := last - first
if err := ds.GetMulti(taskKeys[first:last], tasks[0:taskCount]); err != nil {
finalErr = err
return
} else {
for i := 0; i < taskCount; i++ {
if tasks[i].Status == TaskStatusFailed {
logInfo(c, "failed tasks found")
nextStage = StageFailed
last = -1
finalErr = taskError{tasks[i].Info}
break
} else if tasks[i].Status != TaskStatusDone {
return
}
}
if last >= 0 {
last = first
}
}
}
// running this in a transaction ensures only one process advances the stage
if transErr := runInTransaction(ds, func(ds appwrap.Datastore) error {
job = JobInfo{}
if err := ds.Get(jobKey, &job); err != nil {
return err
}
if job.Stage != expectedStage {
// we're not where we expected, so advancing this isn't our responsibility
stageChanged = false
return errMonitorJobConflict
}
job.Stage = nextStage
job.UpdatedAt = time.Now()
_, err := ds.Put(jobKey, &job)
stageChanged = (err == nil)
return err
}); transErr != nil {
finalErr = transErr
}
if finalErr != nil {
logCritical(c, "taskComplete failed: %s", finalErr)
} else {
logInfo(c, "task is complete")
}
return
}