Cluster setup, random issues with missing tree nodes and ComponentNotFoundException

[Bergmann Manfred <mb...@software-by-mabe.com>]

Hi.

I’m using Wicket 8.4 with Kendo widgets (8.3) in a cluster setup.
Meaning Wicket is configured to use HttpSessionStore and Jetty uses NullSessionCache with a custom SessionDataStore.
All session data goes straight to a backend that distributes the session data.

I have two issues.

One is that when using the Kendo AjaxTreeView and a node is opened and I click on that node it is not in the model anymore.
That is, nodes are loaded lazily and stored inside the TreeViewModel as a field that is serialized as part of the session.
This effect doesn’t always happen though. When it happens I observed that on expanding a node (click to expand) there are two session writes to the store almost concurrently.
The first of the writes has slightly larger data (serialized session data) than the second.
When the expanded node (still visible in browser) is clicked the session is loaded from store, but the last loaded node is missing.
My assumption is that the second write to the store overrides the session data with obsolete data (loaded node missing).

The question here is what triggers this second write to the store. Is it from some client Ajax call?

The second issue is, and probably it’s related.
Sometimes (couldn’t find a pattern yet) when a view is loaded and I click a button (Kendo Button), it is not present on the page anymore, hence a ComponentNotFoundException is thrown.


I’m not exactly certain what I want to ask.
For the first case I found a workaround. The missing node is just re-loaded on demand when it’s missing.
But there is some general quirk here.

Any ideas how to trouble shoot this further?


Regards,
Manfred
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Re: Cluster setup, random issues with missing tree nodes and ComponentNotFoundException

[Bergmann Manfred <mb...@software-by-mabe.com>]

I think I found the issue.

Sorry for bothering.

Doing a network trace shows that there is a component that deploys a JavaScript behavior that triggers a second Ajax call.



Manfred



> Am 26.04.2019 um 10:31 schrieb Bergmann Manfred <mb...@software-by-mabe.com>:
> 
> Hi.
> 
> I’m using Wicket 8.4 with Kendo widgets (8.3) in a cluster setup.
> Meaning Wicket is configured to use HttpSessionStore and Jetty uses NullSessionCache with a custom SessionDataStore.
> All session data goes straight to a backend that distributes the session data.
> 
> I have two issues.
> 
> One is that when using the Kendo AjaxTreeView and a node is opened and I click on that node it is not in the model anymore.
> That is, nodes are loaded lazily and stored inside the TreeViewModel as a field that is serialized as part of the session.
> This effect doesn’t always happen though. When it happens I observed that on expanding a node (click to expand) there are two session writes to the store almost concurrently.
> The first of the writes has slightly larger data (serialized session data) than the second.
> When the expanded node (still visible in browser) is clicked the session is loaded from store, but the last loaded node is missing.
> My assumption is that the second write to the store overrides the session data with obsolete data (loaded node missing).
> 
> The question here is what triggers this second write to the store. Is it from some client Ajax call?
> 
> The second issue is, and probably it’s related.
> Sometimes (couldn’t find a pattern yet) when a view is loaded and I click a button (Kendo Button), it is not present on the page anymore, hence a ComponentNotFoundException is thrown.
> 
> 
> I’m not exactly certain what I want to ask.
> For the first case I found a workaround. The missing node is just re-loaded on demand when it’s missing.
> But there is some general quirk here.
> 
> Any ideas how to trouble shoot this further?
> 
> 
> Regards,
> Manfred


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