[ORCHESTRA-34] NullPointerException triggered by ConversationWiperThread

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3
• Fix Version/s: 1.3.1
• Component/s: Conversation
• Assignee: Unassigned
• Reporter: Simon Kitching
• Created: 17/Dec/08 10:11
• Updated: 12/Jul/09 08:43
• Resolved: 22/Feb/09 14:22

Description

As reported by Petr Juza, a NullPointerException can be triggered by the ConversationWiperThread:
Exception in thread
"org.apache.myfaces.orchestra.conversation.ConversationWiperThread"
java.lang.NullPointerException
at
org.apache.myfaces.orchestra.conversation.ConversationManager.findConver
sationContextId(ConversationManager.java:140)
at
org.apache.myfaces.orchestra.conversation.ConversationManager.removeAndI
nvalidateConversationContext(ConversationManager.java:343)
at
org.apache.myfaces.orchestra.conversation.ConversationManager.checkTimeo
uts(ConversationManager.java:626)
at
org.apache.myfaces.orchestra.conversation.ConversationWiperThread._run(C
onversationWiperThread.java:113)
at
org.apache.myfaces.orchestra.conversation.ConversationWiperThread.run(Co
nversationWiperThread.java:90)

After initial investigation, the problem appears to be that the ConversationWiperThread is detecting a ConversationContext timeout, and so is trying to delete the ConversationContext. However in the ConversationManager.removeAndInvalidateConversationContext(ctx) method, a check is done to see if the context being removed is the "current one", in order to prevent code within a request from accidentally deleting the context that is being used to process that request. However this check requires the FrameworkAdapter - but there is no FrameworkAdapter instance for a background thread like the ConversationWiperThread:

public void removeAndInvalidateConversationContext(ConversationContext context)
{
.....
if (context.getIdAsLong().equals(findConversationContextId()))
...

where findConversationContextId tries to use FrameworkAdapter to look in the current HttpRequest object.

Here, we could check whether a FrameworkAdapter exists, and if not then assume that the context is not the "current" one. Ideally, we would actually block the wiper thread from deleting a context if it is "locked", but the odds of a context timing out while actually in use are very low indeed.

I'm a little puzzled why I don't see this exception in the logs for my apps that use Orchestra...

Note that this exception is fairly harmless: it just disables the ConversationWiperThread

Issue Links

• is duplicated by: ORCHESTRA-41 NullPointerException in method findConversationContextId