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https://issues.apache.org/jira/browse/WICKET-4665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420308#comment-13420308
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Martin Grigorov commented on WICKET-4665:
-----------------------------------------
I think Matej have implemented this functionality and I didn't have the chance
someone to explain it to me. So this is how I understood it by reading its
JSDoc and follow the logic in the code:
the already fired request doesn't count, only the requests in the queue count.
That is, the already fired request should not be stopped (this will lead to
"the client aborted the connection" exceptions), the "busy" flag is there to
prevent more than one Ajax requests on the same channel to be fired in the same
time.
DROP and QUEUE affect only the queue of waiting requests.
If DROP was supposed to drop all requests but the one that is currently being
executed then the JSDoc would say that it allows only the *first* request, not
the *last*.
We may add a third value for AjaxChannel.Type for this new behavior though.
> AjaxChannel.Type.DROP actually allows 2 requests in the "total queue"
> ---------------------------------------------------------------------
>
> Key: WICKET-4665
> URL: https://issues.apache.org/jira/browse/WICKET-4665
> Project: Wicket
> Issue Type: Bug
> Components: wicket
> Affects Versions: 6.0.0-beta3
> Reporter: Christian Oldiges
>
> The schedule JavaScript function of the ajax channel uses a BUSY flag and a
> request queue in a callbacks array.
> If the channel is marked as busy because there is a request currently being
> executed, the second part of the function is executed and for channel type
> DROP, the newly scheduled request is put into the callbacks queue.
> Using this approach, the dropping channel type actually allows 2 requests in
> the "total queue".
> The one that triggers the busy = true which is still running and the one that
> is stored into the callbacks array.
> Reading the documentation of AjaxChannel.DROP says:
> dropping - only the last Ajax request is processed, the others are discarded
> schedule: function (callback) {
> if (this.busy === false) {
> this.busy = true;
> try {
> return callback();
> } catch (exception) {
> this.busy = false;
> Wicket.Log.error("An error occurred
> while executing Ajax request:" + exception);
> }
> } else {
> Wicket.Log.info("Channel busy - postponing...");
> if (this.type === 's') { // stack
> this.callbacks.push(callback);
> }
> else { /* drop */
> this.callbacks = [];
> // THIS IS WRONG this.callbacks[0] =
> callback;
> }
> return null;
> }
> },
> To make it work, the dropping channel should NOT store the currently
> scheduled request, but simply clear the callbacks array.
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