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Re: [xmlblaster] NPE in ClientSubscriptions.getSubscriptionByOid

David Kerry wrote:

On Wed, Oct 23, 2002 at 11:19:03AM -0400, Russell Chan wrote:

>I'm using XMLBlaster 0.80.  I'm getting a NPE in
>[Oct 18, 2002 4:44:50 PM ERROR
>CbWorker-/node/http:] Unexpected
>exception: java.lang.NullPointerException
>	at
>	at
>	at
>	at
>	at
>	at org.xmlBlaster.engine.callback.CbWorker.run(CbWorker.java:61)
>	at
>	at java.lang.Thread.run(Thread.java:498)
>All of my subscriptions are XPATH based, rather than OID based.. For
>SubscribeKeyWrapper subscribeKey = new
>"//service[.=\""+EventQueueConstants.SERVICE_TEMPLATE_PARSE+"\" and "+
>                    "../type[.=\""+EventQueueConstants.TYPE_RESPONSE+"\"
>and "+
>                    "../id[.=\""+ eventQueueId+"\"]]]","XPATH");
>I'm using primarily volatile messages.  I see the NPE while the sweeper
>thread (for volatile messages) appears to be running.
>I'm going to attach a dump of the xmlblaster state.  I *DO* notice that
>even during a dump xmlblaster complains about the "Can't determine key
>oid" (See the top of the dump).
>I'm obviously doing something wrong here... Insights appreciated :-)
If there are NPEs its not you but xmlBlaster which is fishy.
Can you provide a little demo client reproducing this problem?



Here's some more details...

The exception from the latest CVS cut I get is this:

[Oct 23, 2002 11:10:51 AM ERROR CbWorker-/node/http:] Unexpected exception: java.lang.NullPointerException
       at org.xmlBlaster.engine.ClientSubscriptions.getSubscriptionByOid(ClientSubscriptions.java:210)
       at org.xmlBlaster.engine.ClientSubscriptions.messageErase(ClientSubscriptions.java:285)
       at org.xmlBlaster.engine.RequestBroker.fireMessageEraseEvent(RequestBroker.java:1669)
       at org.xmlBlaster.engine.RequestBroker.eraseVolatile(RequestBroker.java:1318)
       at org.xmlBlaster.engine.queue.MsgQueue.checkForVolatileErase(MsgQueue.java:212)
       at org.xmlBlaster.engine.callback.CbWorker.run(CbWorker.java:61)
       at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:728)
       at java.lang.Thread.run(Thread.java:536)

The first time we get this, it happens under the following circumstances:

1) All clients use XML-RPC protocol
2) Client #1 logs in and subscribes using an XPATH query
3) Client #2 logs in and starts publishing simple messages
4) Client #1 receives messages published by client #2
5) Client #1 is killed
6) xmlBlaster throws the above NullPointer exception when it tries
  to publish to the now non-existent client #2.

For reference, client#2 is publishing messages like this:

<key oid='' contentMime='text/xml'>

And client #1 is subscribing like this:

<key oid='' queryType='XPATH'>//service</key>

Note also that after this event, if I restart client #1, it again starts receiving messages, but xmlBlaster will then start throwing out NullPointerExceptions very frequently (same as one above) and the memory consumption starts growing.

Oi, oi, not nice.
I try to find a free hour tomorrow to reproduce it (if you have some code please send it)