func()

in workflow.go [692:761]

• 47 lines of code
• 13 McCabe index (conditional complexity)

func (w *Workflow) traverseDAG(f func(*Step) DError) DError {
	// waiting = steps and the dependencies they are waiting for.
	// running = the currently running steps.
	// start = map of steps' start channels/semaphores.
	// done = map of steps' done channels for signaling step completion.
	waiting := map[string][]string{}
	var running []string
	start := map[string]chan DError{}
	done := map[string]chan DError{}

	// Setup: channels, copy dependencies.
	for name := range w.Steps {
		waiting[name] = w.Dependencies[name]
		start[name] = make(chan DError)
		done[name] = make(chan DError)
	}
	// Setup: goroutine for each step. Each waits to be notified to start.
	for name, s := range w.Steps {
		go func(name string, s *Step) {
			// Wait for signal, then run the function. Return any errs.
			if err := <-start[name]; err != nil {
				done[name] <- err
			} else if err := f(s); err != nil {
				done[name] <- err
			}
			close(done[name])
		}(name, s)
	}

	// Main signaling logic.
	for len(waiting) != 0 || len(running) != 0 {
		// If we got a Cancel signal, kill all waiting steps.
		// Let running steps finish.
		select {
		case <-w.Cancel:
			waiting = map[string][]string{}
		default:
		}

		// Kick off all steps that aren't waiting for anything.
		for name, deps := range waiting {
			if len(deps) == 0 {
				delete(waiting, name)
				running = append(running, name)
				close(start[name])
			}
		}

		// Sanity check. There should be at least one running step,
		// but loop back through if there isn't.
		if len(running) == 0 {
			continue
		}

		// Get next finished step. Return the step error if it erred.
		finished, err := stepsListen(running, done)
		if err != nil {
			return err
		}

		// Remove finished step from other steps' waiting lists.
		for name, deps := range waiting {
			waiting[name] = filter(deps, finished)
		}

		// Remove finished from currently running list.
		running = filter(running, finished)
	}
	return nil
}