Errandboi

Errandboi is a scheduler that publishes given events to Nats and EMQX. It recieves events via http request and caches them in Redis until their release time, then they get published to either EMQX or Nats or both. After events get published, their status changes to done.

Instructions

Lint and Run

• run docker containers, lint and run app: make all

Build

• build app locally: make run build
• build docker image locally: make run docker-build

Run

• run services: make up
• run docker containers: make run

Scheduling and publish structure

scheduler

func (sch *scheduler) WorkInIntervals(d time.Duration) {  
   ticker := time.NewTicker(d)  
  
   go func() {  
      for {  
         select {  
         case <-ticker.C:  
            sch.Publisher.GetEvents()  
            sch.Publisher.Work()  
         case <-sch.Stop:  
            sch.Publisher.Cancel()  
            sch.Publisher.Wp = workerpool.New(sch.Publisher.WorkerSize)  
  
            ticker.Stop()  
  
            return  
  }  
      }  
   }()  
}

Nats

*creating stream

func (n *Nats) CreateStream() error {  
   stream, _ := n.JSCtx.StreamInfo(ChannelName)  
  
   if stream == nil {  
      in, err2 := n.JSCtx.AddStream(&nats.StreamConfig{  
         Name:     ChannelName,  
  Subjects: []string{SubjectName},  
  MaxAge:   0,  
  Storage:  nats.FileStorage,  
  })  
      if err2 != nil {  
         return fmt.Errorf("cannot create stream %w", err2)  
      }  
  
      stream = in  
   }  
  
   n.Logger.Info("events stream", zap.Any("stream", stream))  
  
   return nil  
}

• publish

func (pb *Publisher) publishEventNats(event Event) {  
   t := natsp.ChannelName + "." + event.Topic  
   if _, err := pb.Nats.JSCtx.Publish(t, []byte(event.Payload)); err != nil {  
      pb.logger.Error("failed to publish event", zap.String("payload", event.Payload),  
  zap.String("topic", event.Topic), zap.Error(err))  
   }  
  
   pb.logger.Info("message published to nats", zap.String("payload", event.Payload))  
}

EMQX

• publish

func (pb *Publisher) publishEventEMQ(event Event) {  
   if token := pb.Mqtt.Client.Subscribe(event.Topic, 0, nil); token.Wait() && token.Error() != nil {  
      fmt.Println(token.Error())  
   }  
  
   token := pb.Mqtt.Client.Publish(event.Topic, 0, false, event.Payload)  
   pb.logger.Info("message published to emq: ", zap.String("payload", event.Payload))  
   token.Wait()  
}

Example

Posting events

• request

curl --request POST '{{baseURL}}/events' \
--data-raw '{
	"type": [ "nats","emqx"],
	"events": [
		{
		"description": "This is an event description",
		"delay": "10s",
		"topic": "topic1",
		"payload": "hello"
		}
	]
}'

• response

{
	"id": "62495362f8358c7b9d83ff4e"
}

Check event status

• request

curl --request GET '{{baseURL}}/events/{{eventId}}/status'

• response

{
	"status": "done",
	"events": [
		{
		"description": "This is an event description",
		"publish_date":"2022-04-11T13:31:28+04:30",
		"status": "Done"
		}
	]
}