a DAG task engine based on asynq

1. prepare asynq server mux

   srv := asynq.NewServer(
   	asynq.RedisClientOpt{Addr: redisAddr},
   	asynq.Config{
   		// Specify how many concurrent workers to use
   		Concurrency: 10,
   		// Optionally specify multiple queues with different priority.
   		Queues: map[string]int{
   			"critical": 6,
   			"default":  3,
   			"low":      1,
   		},
   		// See the godoc for other configuration options
   	},
   )
   mux := asynq.NewServeMux()

   please refer to asynq's doc to figure out more config options.
2. create dagflow service

   svc, err := service.New(&types.Config{
   	Redis: types.RedisConfig{
   		Addr:   "127.0.0.1:6379",
   		Expire: 120,
   	},
       Store: types.StoreConfig{
   	    Type: "redis",
       },
   }, nil)
   if err != nil {
   	log.Fatal("failed to create service", err)
   }

3. create a flow object and register it to dagflow service

   f, err := svc.NewFlow("f1")
   if err != nil {
   	log.Fatal("failed to create flow", err)
   }
   if err = f.Node("n1", incOp); err != nil {
   	log.Fatal("failed to create node", err)
   }
   // for complex dag, you can use RegisterFlowsWithDefinitor
   svc.RegisterFlows(mux, f)

4. start asynq server

   if err := srv.Run(mux); err != nil {
   	log.Fatalf("could not run server: %v", err)
   }

1. create dagflow service, same as step 2 in server side

   svc, err := service.New(&types.Config{
   	Redis: types.RedisConfig{
   		Addr:   "127.0.0.1:6379",
   		Expire: 120,
   	},
       Store: types.StoreConfig{
   	    Type: "redis",
       },
   }, nil)
   if err != nil {
   	log.Fatal("failed to create service", err)
   }

2. create a flow object and register it to dagflow service, same as step 3 in server side except mux should be set to nil

   f, err := svc.NewFlow("f1")
   if err != nil {
   	log.Fatal("failed to create flow", err)
   }
   if err = f.Node("n1", incOp); err != nil {
   	log.Fatal("failed to create node", err)
   }
   // for complex dag, you can use RegisterFlowsWithDefinitor
   svc.RegisterFlows(nil, f)

3. submit dagflow tasks

   svc.Submit("f1", []byte(`1`))

f, err := svc.NewFlow("f1")
if err != nil {
    log.Fatal("failed to create flow", err)
}
if err = f.Node("n1", incOp); err != nil {
    log.Fatal("failed to create node", err)
}

func prepareFlow(f *flow.Flow) error {
	if err := f.Node("l1n1", incOp); err != nil {
		return err
	}
	if err := f.Node("l2n1", incOp); err != nil {
		return err
	}
	if err := f.Node("l2n2", decOp); err != nil {
		return err
	}
	if err := f.Node("l3n1", mulOp, flow.WithAggregator(func (dataMap map[string][]byte) ([]byte, error) {
        l2n1Result := dataMap["l2n1"]
        l2n2Result := dataMap["l2n2"]
        // do anything you want to construct input data for node l3n1
    })); err != nil {
		return err
	}
	if err := f.Edge("l1n1", "l2n1"); err != nil {
		return err
	}
	if err := f.Edge("l1n1", "l2n2"); err != nil {
		return err
	}
	if err := f.Edge("l2n1", "l3n1"); err != nil {
		return err
	}
	if err := f.Edge("l2n2", "l3n1"); err != nil {
		return err
	}
	return nil
}

SwitchNode is a special type node which works like switch case statment in golang

f, err := svc.NewFlow("f1")
if err != nil {
    log.Fatal("failed to create flow", err)
}
if err = f.SwitchNode("n1", func(data []byte) string {
    return "+"
}, map[string]flow.NodeFunc{
    "+": incOp,
    "-": decOp,
}); err != nil {
    log.Fatal("failed to create node", err)
}