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https://issues.apache.org/jira/browse/WICKET-5243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919538#comment-13919538
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Martin Grigorov commented on WICKET-5243:
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Thanks for testing, Guillaume!
I will clean and document the new functionality and push it. It will be part of
6.15.
> JS: High stack size in Function Executor causes "too much recursion"
> --------------------------------------------------------------------
>
> Key: WICKET-5243
> URL: https://issues.apache.org/jira/browse/WICKET-5243
> Project: Wicket
> Issue Type: Bug
> Components: wicket
> Affects Versions: 6.8.0
> Environment: Tested on Firefox
> Reporter: Tobias Haupt
> Labels: javascript, perfomance
> Attachments: WICKET-5243-avoid-recursion.patch,
> WICKET-5243-notify-only-when-async.patch, response.xml, wicket-ajax-jquery.js
>
>
> The Function Executor in wicket-ajax-jquery.js uses recursion and deferred
> calls to the notify() function to ensure synchronous execution of all tasks
> contained in an AjaxResponse.
> Each task calls notif() when it is finished. This causes a recursive call to
> processNext() thus raising the stack for each execution. If there are a lot
> of task to handle, the stack size will increase beyond the possible stack
> size in the client causing a "too much recursion" exception and increasingly
> low performance.
> The deferred execution of notify is only necessary if the task executor has
> to wait for long running tasks to finish at some uncertain point in the
> future. Examples: downloading of external resources (js, css, images). These
> task can call back the executor as soon as they are really finished (e.g.
> load event triggerd).
> The problem is that the majority of tasks don't need to wait but return
> instantly instead. Examples: exchanging components, executing custom
> javascripts that do not use the "|-syntax" to include the notify callback.
> Current fix: The depth of the stack is counted and if a depth of >= 1000 is
> reached, a timeout will interrupt the synchronous task queue execution. A new
> executor will continue with an empty stack.
> Problems with that approach:
> - why 1000?
> - several ajax requests might interrupt each other because the synchronous
> execution is broken.
> - if an executed custom javascript creates a big stack itself (e.g. by using
> jquery a lot) the stack will add to the stack used by the Function Executor
> so that it may still be too big.
> Proposal to fix this: see also the attached patch.
> Another callback notifyContinue() is supported that can be called whenever
> the task will return instantly. This callback avoids the recursive call to
> processNext and continues in a simple loop over all the tasks.
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