[Forum] Duplicate posts via QR since security patch (4.2.0)

[ZeroHour]

Hi
Not sure why but ever since we made the manual edits (and the additional one missed out) quick reply is causing duplicate posts a large amount of the time.
Its not 100% but users are reporting seeing the "You can post twice in X seconds" when submitting a reply to find a double post.
We have merge double posts disabled (set to 0) because we didnt need it and this problem didnt seem to happen prior to the security patch.

Any thoughts?

[Wayne Luke]

This is a known issue that has occurred before the security patch. There are several issues in JIRA covering different aspects of the problem.

[ZeroHour]

Which is why we have not updated to 4.2.2, 4.2.0 pre this change didnt have the issue at all. Limiting ajax in admincp fixes the issue (it appears to) but breaks QR image attachments.

[Zachery]

From what I understand, the issue is caused in part by notices/warnings/depreciated messages occurring in the ajax responses. Upgrading to 4.2.2 and using the SKIP errors line should help resolve this.

[ZeroHour]

From what I understand, the issue is caused in part by notices/warnings/depreciated messages occurring in the ajax responses. Upgrading to 4.2.2 and using the SKIP errors line should help resolve this.

Thanks for that, very useful clue. I will go hunt and see what I find. The biggest weirdness is that it doenst happen for most people, only occasionally and only really started happening on our 4.2.0 after I did the edits.

[ZeroHour]

It does appear to be ajax related, disabling ajax in admincp removed the problem for now but thats not exactly a solution.

[Wayne Luke]

It happens because the user sends the ajax request and before the server replies that has received the request, the user sends a normal request. So the server ends up with two copies at the same time and processes them in order. The check for duplicates fail because the original user request hasn't processed yet. It is known as a race condition.

In a perfect environment, it won't occur because the server is quick enough to respond without the second request being sent. Do you frequently have locks on your tables?

[Sherrie]

This looks like the problem I have been getting for the past month on 4.2.2 with skip all errors in config.php. my.cnf has been optimised thanks to some very helpful suggestions by George many months ago. I now have hooks globally disabled and it still hasn't stopped. It seems to be very intermittent and gets really bad then settles down for a couple of days only to come back. Its enough to make people not want to post when it is happening. I just have the one site running on a VPS (knownhost).

[Mark.B]

To troubleshoot this, please could you start your own thread, and provide the information requested here:
http://www.vbulletin.com/forum/node/4005557