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https://issues.apache.org/jira/browse/WICKET-5588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15902628#comment-15902628
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Daniel Stoch edited comment on WICKET-5588 at 3/9/17 7:57 AM:
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I am still trying to resolve this problem (my local patch does not work in all
cases). So for now I see 2 possible solutions, which Emond described earlier:
1. Use the same websocket connection for ajax updates.
2. Ordering responses (which requires solving such problems as: lost responses,
timeouts, maybe some kind of redelivery, etc...).
I have look again on your patch Martin (solution 1):
{quote}
I've implemented Emond Papegaaij's idea of pushing the Ajax response via the
WebSocket connection.
{quote}
As I said in my previous comment this does not work well for me. But now I have
change this implementation getAjaxRequestTargetProvider() method to have much
simpler "if" condition:
{code}
if (connection != null) {
target = new WebSocketRequestHandler(context, connection);
} else {
target = new AjaxRequestHandler(context);
}
{code}
And it looks promising (I must do more tests).
I have a couple of questions:
1. Why in your example patch you have wrapped WebSocketRequestHandler (ws)
inside AjaxRequestHandler, and you do not return ws directly?
2. ws.respond() call is inside detach() method - what is the reason of this
(maybe it is a source of my problems when I tested this solution for the first
time last year)?
3. Currently I have found an issue that listeners (IListener) does not work -
this is natural because it is not implemented in WebSocketRequestHandler. What
do you think to add such implementation (as it is in AjaxRequestHandler)?
was (Author: interface):
I am still trying to resolve this problem (my local patch does not work in all
cases). So for now I see 2 possible solutions, which Emond described earlier:
1. Use the same websocket connection for ajax updates.
2. Ordering responses (which requires solving such problems as: lost responses,
timeouts, maybe some kind of redelivery, etc...).
I have look again on your patch Martin:
{quote}
I've implemented Emond Papegaaij's idea of pushing the Ajax response via the
WebSocket connection.
{quote}
As I said in my previous comment this does not work well for me. But now I have
change this implementation getAjaxRequestTargetProvider() method to have much
simpler "if" condition:
{code}
if (connection != null) {
target = new WebSocketRequestHandler(context, connection);
} else {
target = new AjaxRequestHandler(context);
}
{code}
And it look promising (I must do more tests).
I have a couple of questions:
1. Why in your example patch Martin you have wrapped WebSocketRequestHandler
(ws) inside AjaxRequestHandler, and you do not return ws directly?
2. ws.respond() call is inside detach() method - what is the reason of this
(maybe it is a source of my problems when I tested this solution for the first
time)?
3. Currently I have found an issue that listeners (IListener) does not work -
this is natural because it is not implemented in WebSocketRequestHandler. What
do you think to add such implementation (as it is in AjaxRequestHandler)?
> 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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