[jira] [Commented] (WICKET-5588) Mixing Ajax and push (Atmosphere/native-websockets) updates does not respect order

["Daniel Stoch (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WICKET-5588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956830#comment-15956830 ] 

Daniel Stoch commented on WICKET-5588:
--------------------------------------

{quote}
1. Use the same websocket connection for ajax updates.
{quote}
Unfortunately it does not always work as expected and there are some limitations in implementation.

So for now I am trying to go with this solution:
{quote}
2. Ordering responses (which requires solving such problems as: lost responses, timeouts, maybe some kind of redelivery, etc...).
{quote}
So I want to add some ordering information (key-value) to responses for both ajax and websocket. This information then will be read on client side (JS) to handle proper processing order of responses. But I cannot find a good entry point to add such generic information (order information should be calculated in context of page/component). Any ideas how to add such information to response in Wicket 6.x?

> Mixing Ajax and push (Atmosphere/native-websockets) updates does not respect order
> ----------------------------------------------------------------------------------
>
>                 Key: WICKET-5588
>                 URL: https://issues.apache.org/jira/browse/WICKET-5588
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket, wicket-atmosphere, wicket-native-websocket
>    Affects Versions: 6.15.0, 6.21.0
>            Reporter: Daniel Stoch
>            Assignee: Emond Papegaaij
>         Attachments: 5588-ajax-thru-websocket.tgz
>
>
> As far as I know in Wicket ajax calls by default using the same channel and they are queued. But in wicket-atmosphere integration on the client side the refreshing is done by calling (inside wicket-atomosphere.js):
>   Wicket.Ajax.process(response.responseBody);
> It looks like Wicket.Ajax.process() function does not use channels management, so it can result in out-of-order response processing. This method was added to support Atmosphere push calls in Wicket. See the commit (for issue: WICKET-4668):
> https://github.com/apache/wicket/commit/130b063722e55510f2b2a3b47889e14210a5a32f
> *Example scenario to reproduce this problem:*
> When we try to refresh a component (panelA) via ajax when two different threads in the "same" time perform such refresh.
> 1. The first thread (thread1) is a standard servlet container thread to handle user request from a browser:
> - user clicks AjaxLink and on onClick method panelA is refreshed by target.add(panelA).
> 2. The second thread (thread2) is a notification from a backend system which causes a panelA refreshing too:
> - it can be done for eg. using Atmosphere integration by EventBus.post() - panelA is refreshed by target.add(panelA) too.
> On the server side only one thread can access a page at a time so everything is "queued" properly: the thread1 panelA refresh is executed, then the thread2 refresh code is fired.
> But it looks like on the client side the order of ajax calls is undefined: sometimes JS code added from the thread1 is executed as first, sometimes as a second one. On my computer this order almost always is wrong. It leads to an incorrect situation when the component state on a server is different than the DOM tree on the client browser (so for example user can clicks not existing link).



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