App Functions SDK - Background Publishing

Note

The Background Publishing capability has been deprecated in EdgeX 3.1 and will be removed in the next major release. Use the Service Publish/PublishWithTopic or Context Publish/PublishWithTopic APIs instead.

Application Services using the MessageBus trigger can request a background publisher using the AddBackgroundPublisher API in the SDK. This method takes an int representing the background channel's capacity as the only parameter and returns a reference to a BackgroundPublisher. This reference can then be used by background processes to publish to the configured MessageBus output. A custom topic can be provided to use instead of the configured message bus output as well.

Example - Background Publisher

func runJob (service interfaces.ApplicationService, done chan struct{}){
    ticker := time.NewTicker(1 * time.Minute)

    //initialize background publisher with a channel capacity of 10 and a custom topic
    publisher, err := service.AddBackgroundPublisherWithTopic(10, "custom-topic")

    if err != nil {
        // do something
    }

    go func(pub interfaces.BackgroundPublisher) {
        for {
            select {
            case <-ticker.C:
                msg := myDataService.GetMessage()
                payload, err := json.Marshal(message)

                if err != nil {
                    //do something
                }

                ctx := svc.BuildContext(uuid.NewString(), common.ContentTypeJSON)

                // modify context as needed

                err = pub.Publish(payload, ctx)

                if err != nil {
                    //do something
                }
            case <-j.done:
                ticker.Stop()
                return
            }
        }
    }(publisher)
 }

 func main() {
    service := pkg.NewAppService(serviceKey)

    done := make(chan struct{})
    defer close(done)

    //pass publisher to your background job
    runJob(service, done)

    service.SetDefaultFunctionsPipeline(
        All,
        My,
        Functions,
    )

    service.Run()

    os.Exit(0)
  }