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<== Date ==> <== Thread ==>

Subject: CAJ 1.0.4 issues
From: "Chu, Paul C." <chuc@ornl.gov>
To: tech-talk@aps.anl.gov
Date: Mon, 17 Apr 2006 10:03:10 -0400
We have been heavily using the CAJ with our machine here at SNS for a month or so.  So far we've seen the following issues:

1. if an app needs to connect to a large number of PVs, say > 1000, the app has to connect (at least request connections for) these PVs all at the beginning.  If not doing so, the latter PV connection requests would never succeed.  Also, we need to add a lot of "flushIO()" everywhere to keep "pushing" channel access requests to the server.

2. sometimes, when a lot of PV connections dropped, they have hard time to connect back.  For a small number of dropped PVs, the re-connectivity is fine.

3. we got the following Java exception when connecting to many fast updating PVs (in this case, 2Hz PV update rate and > 160 PVs):

java.nio.BufferUnderflowException
        at java.nio.Buffer.nextGetIndex(Buffer.java:404)
        at java.nio.HeapByteBuffer.getShort(HeapByteBuffer.java:285)
        at com.cosylab.epics.caj.impl.DBRDecoder.readValues(DBRDecoder.java:265)
        at com.cosylab.epics.caj.impl.DBRDecoder.getTimeDBR(DBRDecoder.java:439)
        at com.cosylab.epics.caj.impl.DBRDecoder.getDBR(DBRDecoder.java:115)
        at com.cosylab.epics.caj.impl.requests.EventAddRequest.response(EventAddRequest.java:171)
        at com.cosylab.epics.caj.impl.handlers.EventAddResponse.internalHandleResponse(EventAddResponse.java:60)
        at com.cosylab.epics.caj.impl.handlers.AbstractCAResponseHandler.handleResponse(AbstractCAResponseHandler.java:114)
        at com.cosylab.epics.caj.impl.CAResponseHandler.handleResponse(CAResponseHandler.java:117)
        at com.cosylab.epics.caj.impl.CATransport.processRead(CATransport.java:373)
        at com.cosylab.epics.caj.impl.CATransport.handleEvent(CATransport.java:272)
        at com.cosylab.epics.caj.impl.reactor.lf.LeaderFollowersHandler.handleEvent(LeaderFollowersHandler.java:70)
        at com.cosylab.epics.caj.impl.reactor.Reactor.processInternal(Reactor.java:367)
        at com.cosylab.epics.caj.impl.reactor.Reactor.process(Reactor.java:262)
        at com.cosylab.epics.caj.impl.reactor.lf.LeaderFollowersHandler.run(LeaderFollowersHandler.java:84)
        at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:595)

The 3rd problem only shows on our accelerator network (Linux kernel 2.6.9), not our office network which running with PV gateway and different OS (Linux kernels > 2.6.10 and Windows XP SP2).

For the same applications, we don't see any of the above problems with the JCA/JNI.  

The good side of the CAJ is that it's performance is a lot better than the JCA/JNI.

Has anybody else seen these symptoms?  Any suggestions?  


Thanks,
Paul Chu




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