[jira] [Comment Edited] (WW-3957) Multiple concurrent AJAX requests can collide

["victorsosa (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/WW-3957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15176267#comment-15176267 ] 

victorsosa edited comment on WW-3957 at 3/2/16 7:06 PM:
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This was fixed on issue WW-4573 using a CopyOnWriteArrayList. This is to keep Memory consistency on the ValueStack.

Location: RENDER_DIRECT_LOCATION is no managed but it is enough with the value stack and beside add more locking can affect performance.


was (Author: victorsosa):
This was fixed on issue WW-4573 using a CopyOnWriteArrayList. This is to keep Memory consistency on the ValueStack.

> Multiple concurrent AJAX requests can collide
> ---------------------------------------------
>
>                 Key: WW-3957
>                 URL: https://issues.apache.org/jira/browse/WW-3957
>             Project: Struts 2
>          Issue Type: Bug
>          Components: Plugin - Portlet
>    Affects Versions: 2.3.8
>         Environment: Liferay/Tomcat
>            Reporter: Donat Iszak
>             Fix For: 2.5
>
>
> If there are multiple AJAX request in the same time (and same HTTP Session) they can somehow overwrite the concurrent thread's data (for example the result location).
> Update:
> There is no conflict when we use resource URL, but when we use the action URL the struts2 portlet plugin executes the interceptor stack twice:
> - First in Action phase: This runs normally the action, and saves the full stack and response location to the http session. The PortletStateInterceptor saves the stack, the PortletResult saves the location.
> - Second in Render phase: This phase restores the value stack and runs a dummy action (DirectRenderFromEventAction) which does noting but returns the previously saved response location from the session.
> The problem is that key for the http session objects is a constant (Location: RENDER_DIRECT_LOCATION, Valuestack: STACK_FROM_EVENT_PHASE).
> Let's see an example, when there are two concurrent thread A,B:
> 1. A action phase  (saves locationA to session(RENDER_DIRECT_LOCATION), saves stackA to session(STACK_FROM_EVENT_PHASE))
> 2. B action phase (saves locationB to session(RENDER_DIRECT_LOCATION), saves stackB to session(STACK_FROM_EVENT_PHASE), so it overwrites locationA, stackA!)
> 3. A render phase (loads stackB, locationB from session. Returns/forwards to locationB) So it returns the response of the B thread too!
> 4. B render phase (loads stackB, locationB from session. Returns/forwards to locationB)
> Possible solution is to add the threadId to the session key (RENDER_DIRECT_LOCATION + ThreadId). This could cause a massive load to the session so some clever clean up needed.



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