I am building a message application.. in which the UI should get notified when the new message come in the system...
What is best way to achieve it?..
One way is to create a background task that will poll server every one minute to see if there are any new messages in last one minute..
If this is the case then, where would this code of polling should go?.. because.. this task should be initiated every time user logs in into the system.
Is there any other way through which server will notify the UI as and when there are new messages in the system and UI will refresh itself to show some animation to depict that there are new messages in the system..
As of the current RAP version (2.3) you are able to push updates from the server to the client. Your weapon of choice would be ServerPushSession.
For more information and example code see the RAP developer guide on "Server Push" .
Related
I started an app with some events in event store. As I understand, read model building starts on first read model request. But of course on first start it is no ready yet, but state is returned instantly. So on the client side on each first page open after a server refresh I have an incorrect state that break down my client app.
My question is how can I avoid getting stale data on the client if read model is still being rebuilt?
At the moment, reSolve read model has no information if it is still building, therefore query resolver just use the current state of the read model, whatever it is.
Currently there is no way to wait for rebuild to finish, or to throw an error.
We've recorded an issue and will fix this in the future release.
I am wondering if there is a way to trigger message box on server side.
My case is that I have some logic on server side of the scout application. In the middle of the process some decision need to be made. It this case I would like to trigger message box with YES, NO, CANCEL options.
The way my logic works it really hard to split it into two functions and call one first, ask question and call another with on answer. So this is out of the way for me.
If it is not possible to triggered message box on scout service, is there a way to "mimic" it. So call service method, in the middle pause it, go to client side, present messsage box, return to same service method and continue it.
Why do I need this:
I have dependencies graph (between fields) implemented on scout server side.
After one field has been changed, the whole dependencies graph will be resolved.
One node of the graph has some logic that need user interaction. Problem is that I don't know if this method will be called (dependent on a graph), and if after this method other nods will be called.
You have asked a very similar question few months ago:
Scout Eclipse present optional message on server side
MessageBox is a client concept (package is: org.eclipse.scout.rt.client.ui.messagebox).
You need to transfert the data you need from the server to the client and intercept this information client-side to display the message box you want.
As Jmini already said, MessageBox is a client concept. What you can do is sending back a status (from server to client), checking it on client side and show an appropriate message (box). But then you interrupt your service method and cannot go on where it stopped (alternatively you can throw a VetoException, but this interrupts your service method aswell, so same problem). In my opinion, it is also not a good design to 'request' a user interaction from server side, because in this case, the server side has to wait for the user to respond.
I suggest, if possible, to split your logic into different parts. At first, you execute the first part until you reach the point where you need the user interaction. Then you could save the current state of execution, return to client and show the message. After the user has responded, you should start the 'second' execution, depending on the user's input. This second execution should be started by calling another (new) service, which at first should load or restore the state of the execution saved before requesting the user input.
I'm trying to implement a basic but flexible "event queue" so that my web app can go run subs asynchronously. The way I have working for me now is the app writes a record to an "event queue" table in my database with info on what to do and when to fire. Then I have a daemon script that queries that table periodically and if something needs to be done, it fires it off.
I'd like to start moving towards watchers using something like AnyEvent or EV so I'm not hitting my database so often, but try as I might, I can't find good info on "best practices" for setting something like this up. AnyEvent's documentation is pretty good, but it seems to assume you know how your events should be passed around...which I don't.
What should my watcher be watching? A file? If so, what should be in that file? I don't need to send a whole bunch of data around, I just basically need something that says, "go off and run this sub right now"
I would greatly appreciate someone pointing me in the right direction.
EDIT:
It's been requested that I be more specific: The events I'm trying to fire are various. Sometimes it's an email that needs sending, sometimes it's some DB work, sometimes I just need an action to be delayed for a few hours or days. In all cases, I have some sort of backend script to handle the action, I just need a way for my frontend (web app) to tell my backend, "hey I need you to go do this in x minutes" or "I need you to do this now"
You might look at Mojolicious which is built to be non-blocking and respond asynchronously. It even uses EV internally if you have it installed. To get started read the doc for Mojolicious::Lite and then the Guides (in order) from here: http://mojolicio.us/perldoc
So what is it that you are actually trying to do? Until you describe what it is you actually need, I can't help you any further that that.
There are some CPAN modules in order to run asynchronous tasks via message queues. Examples:
Queue::DBI
POE::Component::MessageQueue
Any::MQ
So I currently have an application independent of Play which may take a long time in its execution.
I want to put a UI on top of it using Play where the application may be invoked and to display some of the details of the execution inside of the application to the user. I would like the page to be updated automatically as the execution proceeds e.g. if a variable in the application increments this would be reflected on the page.
I'm not sure where to begin with this - do I need to split the application up into models + controllers ? Or do I just need to have code in a controller to instantiate the classes I have already coded and call the methods I need ?
What about constantly showing the execution state on the page?
Any resources I should know about/read ? Code examples?
Thanks
You may have already done so, but a good starting point is to create a skeleton Play application using the play new command, while referring the creating a new application section. You will have "views" (HTML template pages) and one controller (in Application.scala). You could add more controllers, but as you will have just a single page that should suffice.
You can add jars from your app (if it's a JVM app) to the lib directory of your Play application. From this: "Or do I just need to have code in a controller to instantiate the classes I have already coded and call the methods I need?" it sounds like you would be happy to have your app run in the process of the Jetty + Play server. Check out the Global object for starting your app at process startup.
Check out the section on comet sockets for sending updates from the Play app to the browser. You'll need a bit of Javascript in the web page.
Do you want to have this application running outside of play, perhaps on another server? Can you modify the application, or is this 3rd party software?
If so, you have to have some way to send data back and forth between your play front end and your application. You can either have your application expose a websocket, and then your play front end and your application can push data back and forth to each other. You can then have your client page have a websocket open to you play front end, and then play can push the updates to the client. If your application can't support a websocket, you could also expose some URLs on your front end for the application to POST to. You can then use some sort of message bus or database mechanism (RabbitMQ, redis, Mongo capped collection, or even just a shared Queue object) so that the front end websocket can get those updates and send them to the client.
I have an iPad app that works both on and offline but when I am offline there are web service calls that will need to be made once online availability is an option again.
Example:
A new client is added to the app, this needs to be sent to the web service but since we are offline we dont want to slow the user down so we let them add locally and keep going but we need to remember that that call needs to be made to the web service when we can. Same thing for placing orders and such.
Is there some sort of queue that can be setup that will fire once we have connectivity?
I don't think the overhead of a heavyweight tool like MSMQ is needed for a simple action. You can use Core Data, persist managed objects with the data needed to call the web service, and only delete each managed object after a successful post. There might or might not be a way to capture an event when connectivity starts, but you can certainly create a repeating NSTimer when the first message is queued and stop it when there are no messages in the queue.
This library handles offline persistent message queueing for situations like you describe. It says alpha from a year ago, but I have confirmed it is used in production apps:
https://github.com/gcamp/IPOfflineQueue