Hands-On Software Engineering with Golang

The master's executor factory

The code for generating an executor factory for the master is quite similar; to avoid repeating the same code blocks again, we will only list the implementations for each one of the individual callback wrappers, starting with preStepCallback:

func (f *masterExecutorFactory) preStepCallback(ctx context.Context, g *bspgraph.Graph) error {    if _, err := f.barrier.WaitForWorkers(proto.Step_PRE); err != nil {        return err    } else if err := f.barrier.NotifyWorkers(&proto.Step{Type: proto.Step_PRE}); err != nil {        return err    }    if f.origCallbacks.PreStep != nil {        return f.origCallbacks.PreStep(ctx, g)    }    return nil}

Compared to the worker-side implementation, the master behaves a bit differently. To begin with, the master ...